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Dopamine and Serotonin Interactively ModulatePrefrontal Cortex Neurons In VitroNina C. Di Pietro and Jeremy K. Seamans

Background: Dopamine (DA) and serotonin (5-HT) are released in cortex under similar circumstances, and many psychiatric drugs bind toboth types of receptors, yet little is known about how they interact.

Methods: To characterize the nature of these interactions, the current study used in vitro patch-clamp recordings to measure the effects ofDA and/or 5-HT on pyramidal cells in layer V of the medial prefrontal cortex.

Results: Either DA or 5-HT applied in isolation increased the evoked excitability of prefrontal cortex neurons, as shown previously.Coapplication of DA and 5-HT produced either a larger increase in excitability than when either was given alone or a significant decrease thatwas never observed when either was given alone. Dopamine or 5-HT also “primed” neurons to respond in an exaggerated manner to thesubsequent application of the other monoamine.

Conclusions: These data reveal the unappreciated interactive nature of neuromodulation in cortex by showing that the combined effectsof DA and 5-HT can be different from their effects recorded in isolation. On the basis of these findings, we present a theory of how DA and5-HT might synergistically modulate cortical circuits during various tasks.

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Key Words: Dopamine, electrophysiology, modulation, plasticity,prefrontal cortex, serotonin

M onoamines regulate prefrontal cortex (PFC) function, andtheir dysregulation plays an important role in a number ofpsychiatric and neurological disorders. Accordingly,

highly selective serotonin (5-HT) reuptake inhibitors are widely pre-scribed for depression, and catecholamine reuptake inhibitors arewidely prescribed for ADHD, whereas atypical antipsychotic medi-cations for schizophrenia target multiple monoamine receptors(1–3). Despite the success of such drugs, basic research is still strug-gling to understand the rudimentary operating principles of mono-aminergic systems. In most cases, this involves investigating theeffect of a given monoamine in isolation. Although this approachhas lead to a wealth of knowledge, it is important to bear in mindthat a given monoamine is seldom released in isolation. For in-stance, a variety of events evoke both the release of dopamine (DA)and 5-HT, including stress (4,5), food consumption (6,7), condi-tioned taste aversion (8), ethanol consumption (9,10), and exercise(11). Moreover, DA and 5-HT receptors coexist in the PFC (12–14),and many of their intracellular signaling pathways overlap (15).

Early work by Iyer and Bradberry (16) demonstrated a functionalinteraction between 5-HT and DA systems in PFC as 5-HT applica-tion (1–10 �mol/L) increased extracellular DA in a dose-dependentmanner, an effect likely mediated by 5-HT1 receptors (17–19). Inaddition, Westerink et al. (20) demonstrated that coadministrationof a 5-HT2A antagonist with a D2 antagonist increased DA release inthe medial PFC to an extent that was significantly greater than thatobserved after application of either antagonist alone (18). Thesestudies suggest that it is not only the case that multiple mono-amines might be released simultaneously, but once released theyinteract in a complex nontrivial manner.

From the Brain Research Center, Department of Psychiatry, University ofBritish Columbia, Vancouver, British Columbia, Canada.

Address correspondence to Jeremy Seamans, Ph.D., University of BritishColumbia, Department of Psychiatry, Brain Research Center, KoernerPavilion, UBC Hospital, 2211 Wesbrook Mall, room F-241, Vancouver, BCV6T 2R5, Canada; E-mail: [email protected].

ieceived Apr 19, 2010; revised Aug 4, 2010; Aug 9, 2010.

0006-3223/$36.00doi:10.1016/j.biopsych.2010.08.007

Here we used patch-clamp recordings to investigate the effectsf bath application of DA or 5-HT applied singly, concurrently, orequentially on the evoked firing of deep layer PFC neurons in brainlices. We replicated previous studies by showing that DA or 5-HTould alone increase the excitability of these neurons (21–26); how-ver, when coapplied they either produced a larger increase inxcitability than either alone or a decrease in firing that was neverbserved when either was applied alone. Furthermore, the priorpplication of either 5-HT or DA could prime PFC neurons to re-pond in an exaggerated manner to the other monoamine appliedome 20 min later. Thus, 5-HT and DA can interact in unexpectedays to modulate the basic excitability of PFC neurons.

ethods and Materials

Detailed descriptions of brain slice preparation, whole-cellatch-clamp recordings, and drugs are provided in Supplement 1.

xperimental ConditionsFor priming experiments, baseline recordings were taken for 10 min,

ollowed by bath application of either the DA (n�6) or 5-HT (n�6) primeor 5 min, a 20-min washout, then bath application of the other mono-mine (either 5-HT or DA) for 5 min, and a 20-min washout. For concomi-ant bath application of DA and 5-HT (n � 13), baseline recordings wereaken for 10 min before drug applications (5 min), followed by at least a0-min washout period. Drug controls were obtained by recording theffectsofDAor5-HTaloneaftereithera10-min(DA[n�10];5-HT[n�12])r45-min(DA[n�7];5-HT[n�6])baselinerecordingperiod, followedby35-min washout. Recording solution always contained 10 �M bicucull-

ne and 6-cyano-7-nitroquinoxaline-2,3-dione to block �-aminobutyriccid (GABA)A and �-amino-3-hydroxy-5-methylisoxazole propionate cur-ents, respectively.

esults

Detailed descriptions of data analysis methods are provided inupplement 1. We first quantified the effects of bath application ofither 10 �M 5-HT or 20 �M DA on firing in response to a fixedurrent pulse that would evoke approximately 4 – 6 spikes at base-

ine. As shown previously, DA (mean increase � 30 � 6.3%, p � .05)r 5-HT (mean increase � 104.8 � 9.5%, p � .001) application alone

ncreased excitability (Figures 1A and 1B) (Figure S2 in Supplement

BIOL PSYCHIATRY 2011;69:1204–1211© 2011 Society of Biological Psychiatry

mailto:[email protected]

N.C. Di Pietro and J.K. Seamans BIOL PSYCHIATRY 2011;69:1204–1211 1205

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1206 BIOL PSYCHIATRY 2011;69:1204–1211 N.C. Di Pietro and J.K. Seamans

1) to an extent consistent with past studies. To assess the effectsacross a large activity range, we also analyzed the slope of thefrequency-current (F/I) curve or gain across multiple steps. EitherDA (mean increase in slope � .49 � .10, p � .001) or 5-HT (meanncrease in slope � 1.04 � .17, p � .001) application increased the

slope of the F/I curve (Figure 1C), although the effects were mostprominent on the initial slope (i.e., at lower current steps) (Figure S1in Supplement 1). These effects of DA and 5-HT alone closely repli-cate the findings of Thurley et al. (25) and Zhang and Arsenault (26),respectively.

Next we examined the effects of sequential application of 5-HT(10 �M) and DA (20 �M). Bath application of DA when preceded 20

in earlier by 5-HT resulted in an increase in firing activity (meanncrease � 38 � 3.9%) that was greater in magnitude than when DA

was applied at the same time point in the absence of 5-HT pretreat-ment (mean increase � 22 � 3.0%, p � .01) (Figure 1D). The slope ofthe F/I curve was not only increased by DA when it was followed by5-HT pretreatment relative to its own baseline (mean increase �1.03 � .15, p � .01), but the relative increase in the slopes of primedcells was significantly greater than the relative increase in theslopes of nonprimed cells (Figure 1E) (p � .05). This suggests thatprior 5-HT exposure made PFC neurons more sensitive to subse-quent DA application.

When cells were first primed with DA, later application of 5-HTalso led to an overall increase in firing rates (mean increase � 77.4 �7.5%) that was greater (p � .03) than the increase observed in theabsence of DA pretreatment, for a given current pulse (mean in-crease � 59.7 � 4.9%) (Figure 1F). The slope of the F/I curve was alsoncreased by 5-HT (mean increase � 0.53 � .14, p � .02) when it was

followed by DA pretreatment, but in this case the relative increasein the slope of primed cells was not significantly greater than therelative increase in the slope of nonprimed cells (Figure 1G, p � .05).However, the initial slope of primed cells was significantly greaterthan baseline (Figure 1G, p � .05), suggesting that although thepriming effect of 5-HT on DA occurred across the entire input/output range, the priming effect of DA on 5-HT was limited to onlyone or two current steps in the middle range of intensities.

Finally we investigated the effects of simultaneous coapplica-tion of DA (20 �M) and 5-HT (10 �M). Coapplication resulted in oneof two opposing effects; approximately one-half of the recordedcells responded with a massive increase in firing rate (mean in-crease � 211 � 43.7%, p � .01; peaking at approximately 290%),whereas the remaining one-half of the cells were only inhibited(mean decrease � �69 � 22.7%, p � .01) (Figure 2A and 2B) (FigureS2 in Supplement 1). For cells that were increased, the effect wassignificantly larger than that produced by either 5-HT (p � .05) orDA (p � .05) alone (Figure 2B) and was even larger than their linear

4™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™Figure 1. The effects of either dopamine (DA) or serotonin (5-HT) alone on

eurons. (A) Left: baseline responses of two different prefrontal cortex neuroA (20 �M) or (bottom) 5-HT (10 �M), more spikes were evoked by the samvoked spikes were increased significantly (asterisk and number sign) byEM). (C) Frequency-current (F/I) curves for each cell and the slopes of these lilopes of the lines fit to the F/I curves for separate groups of cells during baseA increased the initial slope (asterisks) but not second slope of the F/I curveerotonin produced an initial large increase in the response of a group of neuhe point when DA was applied (gray line and diamonds). The DA-mediatignificantly greater (as denoted by the asterisk) than that observed in cells requares). (E) Slopes of the F/I curves for the same cells shown in D. The astehe group that had been pretreated with 5-HT than the group that had not.o a fixed current pulse that slightly decayed during the following 20 min untncrease in excitability in these cells was greater (as denoted by the asterisk)he experiment (black line and squares). (G) Slopes of the F/I curves for the sa
ne or two current steps in the middle range of intensities; hence the slope chan

um. Because the distribution of the effects was bimodal (Figure 2Bnset), a grouping criterion of � 25% in firing rate was used toategorize cells as either excited or inhibited by DA and 5-HT coap-lication.

Examination of the effects across current intensities for excitedells indicated that only the initial slope was significantly increasedy coapplication (2.86 � �.9 vs. .61 � .23, p � .03) and not theecond slope (1.52 � .36 vs. 1.6 � .15) (Figures 2C and 2D). Thenhibitory effects of concomitant 5-HT and DA application were also

ost evident on the initial slope (1.17 � .1 vs. .29 � .1) and not theecond slope of the F/I curves (1.33 � .14 vs. 1.33 � .28) (Figures 2Cnd 2D). Therefore, although DA and 5-HT were always excitatoryhen given alone, together they produced a larger excitation or a

ompletely novel mode of suppression, approximately one-half ofhe time.

iscussion

The present study investigated the integrative effects of DA and-HT on the electrophysiological properties of PFC neurons. Oneype of comodulation took the form of priming, in that prior appli-ation of DA or 5-HT potentiated the subsequent effect of the otheronoamine. A second type of comodulation was bidirectional in

ature, because in some cells coapplication caused an increase inxcitability that was greater than the increase produced by eithereurotransmitter alone, whereas in the other cells a profound de-ression in spiking occurred. This form of comodulation was unique

n that a decrease in firing was never observed when 5-HT or DA wasiven alone.

otential Cellular MechanismsThe present data are consistent with past studies where DA or

-HT was applied in isolation to PFC neurons in that DA, at theseoncentrations, typically increased evoked excitability by approxi-ately 30%, whereas 5-HT increased it by approximately 100%–

50% (21,23,25–28). However, the present study is the first to exam-ne the combined effects of these two monoamines on the evokedring properties of PFC neurons in brain slices. Under these condi-ions, the most striking effect was the bidirectionality of cell re-ponses.

It is currently unclear as to why some cells exhibited an increasen excitability and others exhibited a decrease upon coapplicationf DA and 5-HT. One reason might be related to the age of thenimals used, with the assumption that monoamines affect PFCeurons differently at different stages of development (29). Accord-

ngly, Zhang (30) showed a developmental decline of 5-HT–in-uced (10 �M) excitatory effects in layer V pyramidal neurons of the

™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™d excitability and the priming effects of 5-HT and DA on prefrontal cortex

a fixed amplitude intracellular current pulse. Right: after application of (top)ent pulse in the two neurons. (B) In separate groups of cells, the number of

DA (black line and diamonds) or 5-HT (gray line and boxes) (mean �ere calculated. The histogram shows the average (and SEM) first and seconderiods and during the 5-min period of 5-HT or DA application. Both 5-HT andicating that the effects were mainly in response to smaller current steps. (D)o a fixed current pulse that slowly decayed during the following 20 min untilcrease in excitability in the cells that received prior 5-HT application wasng only DA at a similar time point 35 min into the experiment (black line anddicates that the relative change in the initial F/I slope by DA was greater inpamine produced an initial increase in the response of a group of neurons

point when 5-HT was applied (gray line and diamonds). The 5-HT–mediatedthat observed in cells receiving only 5-HT at a similar time point 35 min intolls shown in F. Note that the priming effect of DA on 5-HT was limited to only

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Figure 2. Coapplication of dopamine (DA) or serotonin (5-HT) produce qualitatively and quantitatively different effects from those produced by either alone. (A)Representative examples of the two classes of effects produced by DA and 5-HT coapplication. Left: baseline responses of two different prefrontal cortex neurons toa fixed amplitude intracellular current pulse. Right: after coapplication of DA plus 5-HT, many fewer spikes were evoked by the same current pulse in one neuron (top),whereas in the other, many more spikes were evoked. (B) In response to a fixed current step, coapplication increased the number of spikes in approximately one-half

f the cells (gray line and triangles) and significantly decreased the number of spikes in the other one-half (black line and open circles). Dopamine (gray line andiamonds) or 5-HT (gray dashed line and solid squares) alone only increased excitability, and this increase was significantly smaller (asterisks) than the increasebserved when they were coapplied. (C) Example from a single neuron illustrating how the first (solid lines) and second (dotted lines) slope were fitted to the dataoints under baseline conditions (gray circles and lines) and how they were changed by coapplication of 5-HT and DA (black circles and lines). Note that the change

n the first slope was larger than the change in the second slope. (D) Slopes of the F/I curves for the cells receiving coapplication of 5-HT and DA. The asterisks indicatehat there was a significant increase in the first slope for one subgroup of cells and a decrease in the other subgroup.


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rat PFC that peaked at postnatal day (PD) 20 and thereafter re-mained stable. We explored this possibility by examining the ef-fects of concomitant DA and 5-HT application as a function of age ofthe animal. The average age of animals was PD27 for cells thatexhibited an excitatory response and PD26 for inhibited cells. Two-tailed, unpaired t tests revealed that cell responses from rats ages

D21–PD25 were not different (p � .05) from responses obtainedfrom rats ages PD26 –PD35. Thus, age of animal within this rangedid not predict the excitatory or inhibitory types of responses.

Another possible reason for the opposing effects of 5-HT and DAon different neurons might be related to heterogeneity in DA and5-HT receptor expression on individual PFC neurons. Because5-HT1A receptors have been shown to inhibit PFC pyramidal cells(31,32), whereas activation of 5-HT2 receptors increased the excit-ability of PFC neurons (26), it might be the case that we observeddifferent effects because we simply recorded from different groupsof neurons with only 5-HT1 or 5-HT2 receptors. However, this is alsounlikely, because 5-HT1A and 5-HT2A/C receptors are coexpressedin approximately 60% of pyramidal neurons, with much lower per-centages (�15%) of neurons containing only one or the other sub-type (11,13,14,33,34). Hence, 5-HT1A and 5-HT2 receptor activationcan have opposite effects on the same PFC neurons, suggestingthat both receptors are functional on a given neuron in terms ofregulating excitability (27). A similar conclusion can be drawn withregard to DA receptors. Although there seems to be a predomi-nance of D1 over D2 receptors in the PFC overall (35–37, but see 38),on a functional level, a given PFC neuron tends to respond to bothD1 and D2 agonists in vitro (39 – 42). Therefore, it is unlikely that agiven neuron contains only 5-HT1 or 5-HT2 receptors and/or onlyD1 or D2 receptors.

Alternatively, it might be the case that the overall effects ofcoapplication of 5-HT and DA depend on the relative densities ofeach receptor on a given neuron and the ability of these receptorsto effect intracellular signaling pathways. Along these lines, Cai etal. (43) showed that 5-HT4 receptor activation could either increaseor decrease GABA currents in PFC neurons, depending on the pro-tein kinase A (PKA) level of the neuron, with moderate levels in-creasing GABA currents and high PKA levels decreasing the cur-rents. If a similar situation exists for excitability, then coactivation ofDA and 5-HT receptors would have additive effects on the levels ofPKA (or another signaling molecule) and evoke different effectsfrom those produced by more moderate levels of PKA achieved byactivation of either receptor type alone. Given the multitude ofreceptor subtypes and downstream intracellular signaling mole-cules, providing evidence for this hypothesis will be difficult.

What Is the Overall Effect of 5-HT and DA Comodulation?One clue as to the overall impact of comodulation might relate

to claims that 5-HT and DA have compartmentalized actions on PFCneurons. The 5-HT1A receptors are located in the axosomatic re-gion, whereas 5-HT2A are located on the dendrites (14,44,45). At acellular level 5-HT2A receptors are thought to increase excitabilityof PFC neurons by reducing the after-hyperpolarization and induc-ing an after-depolarization (14,26,27). As a result, Amargós-Bosch etal. (14) proposed that the depolarization produced by inputs arriv-ing predominately via the apical dendrites would be increased by5-HT2A receptor activation and this effect would be further ampli-fied by the 5-HT2A–mediated increase in glutamatergic inputs tothis region of the neuron (46). They also suggested that 5-HT1Areceptor activation would inhibit local inputs by a shunting or vetoeffect, given their localization in the proximal axon. This theory forcompartmentalized actions of 5-HT is essentially the converse of
what we proposed for the compartmentalized actions of DA on PFC n

eurons (21,47). We suggested that DA might limit the effects ofynaptic inputs to distal apical dendrites by reducing N-type cal-ium ion currents and by perhaps increasing the hyperpolarization-ctivated cyclic-nucleotide gated currents that is generated in theore distal dendrites (48,49). Conversely, we proposed that be-

ause of the effects of DA on a number of inward and outwardurrents in the proximal dendrites/somatic region, DA might exert aet augmentation of local inputs. These effects would be further aug-ented by DA modulation of GABAergic currents, because DA has

een shown to decrease inputs from fast-spiking GABAergic interneu-ons synapsing close to the soma while enhancing inputs from non–ast-spiking GABAergic interneurons synapsing in the dendrites (50).ollectively, the idea is that DA tends to reduce or filter distal inputshile enhancing the effects of inputs arriving close to the soma, pre-

umably arising from local circuit connections putatively involved inhe generation of recurrent activity patterns. In essence therefore, both-HT and DA neuromodulatory systems might bias PFC neurons toespond differentially to inputs arriving in the distal dendrites gener-lly coming from outside the PFC versus those arriving close to theoma generally arising from within the PFC (47). Hence, coactivation ofA and 5-HT systems could effectively regulate information entering

he PFC, the amount of local activity generated within the PFC, andnally which neurons within the PFC participate in this activity. In thisay the presence of both neuromodulators could provide exquisite

ontrol of PFC network activity not possible with either system alone.An example of how this might be relevant is in regard to the

uning of working memory-related activity within the PFC. DA re-eptor manipulations can improve working memory performancender certain conditions, whereas genetically determined differ-nces in 5-HT and DA systems impact working memory perfor-ance and enhance the efficiency of PFC networks during workingemory tasks (51–54). Furthermore, manipulations of either DA or

-HT receptors affect the firing of primate PFC neurons duringorking memory tasks in remarkably similar ways. Serotonin in-

reases the firing of neurons active during the delay period of aorking memory task but only for preferred target locations,hereas it tends to decrease the firing for nontarget locations (55).

ikewise, D1 receptor agonists preferentially suppress activity foronpreferred memory field locations (56), whereas DA itself in-reased the activity for preferred memory field locations (57).herefore, both DA and 5-HT increase the differentiation in thering rates associated with the encoding of different types of infor-ation during delay periods of working memory tasks.

Recently, we performed an analysis of how networks of rat PFCeurons encode information during working memory tasks and

ound that all task epochs were encoded as unique states or activityatterns across the network (58). The results of Lapish et al. (58) areummarized schematically in Figure 3 (gray box). A critical conclu-ion from this work was that that almost all neurons participated inhe encoding of all task epochs to varying degrees and it was theifferences in the pattern of activity across the neurons as definedy both increases and decreases in firing rates that determined thepoch-specific patterns. What seemed to separate “good” frompoor” behavioral performance on the task was the degree of dif-erentiation in PFC network states associated with each task epoch:

hen rats performed well, each task epoch was associated with veryifferent network states, whereas if the same rats performed poorly

here was little differentiation between activity states as defined byelative changes in the firing rates of the neurons (Figure 3).

It is presently unclear why performance varies on this task, al-hough there does seem to be some correlation with PFC DA levels59). When viewed in light of the present data, DA (acting on a
umber of ionic currents as discussed previously in [60]) might

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increase the firing rate of neurons already activated as part of a taskepoch-specific pattern (e.g., cells 2, 4, 5, and 8 during the choiceperiods of the task in Figure 3). The 5-HT–mediated increase in firingwould also presumably tend to further augment the firing of acti-vated cells. These increases in firing of activated neurons wouldhelp to differentiate the overall activity state associated with eachtask epoch and perhaps result in improved performance.

Although increasing the activity of a subset of neurons is usefulin helping to orthogonalize the patterns, augmenting the de-creases in activity would serve to differentiate each pattern evenfurther. As shown in the present study, at least in terms of current-pulse evoked firing, neither DA nor 5-HT seemed capable of de-creasing PFC activity in isolation. Yet when combined they exertedeither a larger increase in firing rates or a massive decrease in firing.By exaggerating both increases and decreases in firing rates, theoverall effect would be to make each task epoch-specific pattern farmore differentiated (as illustrated schematically in Figure 3) andpresumably aid in the performance of the task.

Although the aforementioned theoretical example was within thecontext of a working memory task, these neuromodulators presum-ably tune the activity of PFC networks in a variety of circumstances. Forinstance, ensembles of PFC neurons also exhibit unique network statesthat encode associative rules, and these network representations shiftabruptly when rats switch between rules on a set-shifting task (61). Inthis context it is of interest that both monoamines are involved inmediating behavioral flexibility, albeit in slightly different manners

Figure 3. A theory of how dopamine (DA) or serotonin (5-HT) might act synea schematic recapitulation of data presented in Lapish et al. (58). By recorddelayed win-shift radial arm maze working memory task, Lapish et al. (58) fou

ays every time the rat participated in a given task epoch (i.e., making choicering rate of each neuron are given by direction and the sizes of the bars ineuron during a given task epoch. The same neurons are presented under va

he deviations in firing rates collectively formed a network state or pattern.erforming poorly (making more than two errors/trial), Lapish et al. (58) foun

performing optimally (committing no errors) the differences in the patternschanges that might be expected to occur in such networks when levels of Deither DA or 5-HT levels in isolation would be expected to augment the deviaa given epoch, while having little effect on the firing rates of neurons that weof activated neurons would help to disambiguate one epoch-specific patternvery large increases and decreases in firing, as shown in Figure 2. Therefore, oof neurons whose rates increased during a given task epoch but in additiondecreased in association with a given task epoch. By accentuating the deviatias each pattern becomes highly differentiated.

(62–63). By accentuating differences in network patterns as proposed

n Figure 3, 5-HT and DA might help to disambiguate different rulesuch that the correct rule is implement at the correct time, withoutontamination from past rule representations.

This type of comodulatory control likely occurs quite often,ecause both DA and 5-HT are released in response to a varietyf similar and quite common events (4 –11). Furthermore, 5-HTan itself evoke the release of DA in the PFC and vice versa19,64). In clinical situations the comodulatory effect can bexploited to a therapeutic advantage, such as in the case whenelective serotonin reuptake inhibitors are given in combinationith bupropion, which acts on the DA system (65). Therefore, the

ype of comodulation described here should be consideredhen trying to understand PFC function in general and perhaps

ould be further exploited in the development of novel pharma-otherapies to treat such monoaminergic-based disorders asepression, drug addiction, attention-deficit/hyperactivity dis-rder, and schizophrenia.

This work was funded by the Canadian Institutes of Health ResearchGrants MOP-93784 and INO-83009). We would like to thank Dr. N. Gore-ova for help with experiments and insightful comments throughout thisroject.

All authors report no biomedical financial interests or potentialonflicts of interest.

ally to modulate prefrontal cortex networks. The images in the gray box areultiple single units in the medial prefrontal cortex of rats performing theat individual neurons deviated from their baseline firing rates in consistentiving rewards, or waiting in the delay period). The deviations from the mean

figure. Thus, each bar represents the deviation in the firing rate of a giventheoretical conditions. When viewed across the 10 neurons in this example,patterns presumably represented some aspect of each task epoch. In ratsthe differences in the epoch-specific patterns were slight. In contrast, in ratssignificantly larger. The series of bars outside the gray box are theoretical

5-HT increase, on the basis of data shown in the present study. Increases inin firing rates only for neurons whose activity was typically increased duringpressed during a given epoch. This selective augmentation in the deviationthe others. However, when DA and 5-HT are present together, they produceould expect not only a further augmentation in the deviations in firing ratesgmentation in the firing rate reductions exhibited by neurons whose ratesfiring rates in both directions the overall effect is a dramatic increase in gain

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Supplementary material cited in this article is available online.


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1. Hagino Y, Watanabe M (2002): Effects of clozapine on the efflux ofserotonin and dopamine in the rat brain: The role of 5-HT1A receptors.Can J Physiol Pharmacol 80:1158 –1166.

2. Dodson WW (2005): Pharmacotherapy of adult ADHD. J Clin Psychol61:589 – 606.

3. Meltzer HY, Huang M (2008): In vivo actions of atypical antipsychoticdrug on serotonergic and dopaminergic systems. Prog Brain Res 172:177–197.

4. Mitsushima D, Yamada K, Takase K, Funabashi T, Kimura F (2006): Sexdifferences in the basolateral amygdala: The extracellular levels of sero-tonin and dopamine, and their responses to restraint stress in rats. EurJ Neurosci 24:3245–3254.

5. Jordan S, Kramer GL, Zukas PK, Petty F (1994): Previous stress increasesin vivo biogenic amine response to swim stress. Neurochem Res 19:1521–1525.

6. Fallon S, Shearman E, Sershen H, Lajtha A (2007): Food reward-inducedneurotransmitter changes in cognitive brain regions. Neurochem Res32:1772–1782.

7. Fetissov SO, Meguid MM, Chen C, Miyata G (2000): Synchronized releaseof dopamine and serotonin in the medial and lateral hypothalamus ofrats. Neuroscience 101:657– 663.

8. Hoebel BG, Mark GP, West HL (1992): Conditioned release of neurotrans-mitters as measured by microdialysis. Clin Neuropharmacol 15(suppl 1Pt A):704A–705A.

9. Bare DJ, McKinzie JH, McBride WJ (1998): Development of rapid toler-ance to ethanol-stimulated serotonin release in the ventral hippocam-pus. Alcohol Clin Exp Res 22:1272–1276.

10. Samson HH, Tolliver GA, Haraguchi M, Hodge CW (1992): Alcohol self-administration: Role of mesolimbic dopamine. Ann N Y Acad Sci 654:242–253.

1. Meeusen R, De Meirleir K (1995): Exercise and brain neurotransmission.Sports Med 20:160 –188.

12. Santana N, Bortolozzi A, Serrats J, Mengod G, Artigas F (2004): Expres-sion of serotonin1A and serotonin2A receptors in pyramidal andGABAergic neurons of the rat prefrontal cortex. Cereb Cortex 14:1100 –1109.

13. Santana N, Mengod G, Artigas F (2009): Quantitative analysis of theexpression of dopamine D1 and D2 receptors in pyramidal and GABAergicneurons of the rat prefrontal cortex. Cereb Cortex 19:849 – 860.

14. Amargós-Bosch M, Bortolozzi A, Puig MV, Serrats J, Adell A, Celada P, etal. (2004): Co-expression and in vivo interaction of serotonin1A andserotonin2A receptors in pyramidal neurons of prefrontal cortex. CerebCortex 14:281–299.

15. Di Pietro NC, Seamans JK (2007): Dopamine and serotonin interactionsin the prefrontal cortex: Insights on antipsychotic drugs and their mech-anism of action. Pharmacopsychiatry 40(suppl 1):S27–S33.

16. Iyer RN, Bradberry CW (1996): Serotonin-mediated increase in prefrontalcortex dopamine release: Pharmacological characterization. J Pharma-col Exp Ther 277:40 – 47.

17. Diaz-Mataix L, Scorza MC, Bortolozzi A, Toth M, Celada P, Artigas F(2005): Involvement of 5-HT1A receptors in prefrontal cortex in themodulation of dopaminergic activity: Role in atypical antipsychotic ac-tion. J Neurosci 25:10831–10843.

18. Ichikawa J, Ishii H, Bonaccorso S, Fowler WL, O’Laughlin IA, Meltzer HY(2001): 5-HT(2A) and D(2) receptor blockade increases cortical DA re-lease via 5-HT(1A) receptor activation: A possible mechanism of atypicalantipsychotic-induced cortical dopamine release. J Neurochem 76:1521–1531.

19. Matsumoto M, Togashi H, Mori K, Ueno K, Miyamoto A, Yoshioka M(1999): Characterization of endogenous serotonin-mediated regulationof dopamine release in the rat prefrontal cortex. Eur J Pharmacol 383:39 – 48.

20. Westerink BH, Kawahara Y, De Boer P, Geels C, De Vries JB, Wikstrom HV,et al. (2001): Antipsychotic drugs classified by their effects on the releaseof dopamine and noradrenaline in the prefrontal cortex and striatum.Eur J Pharmacol 412:127–138.

21. Yang CR, Seamans JK (1996): Dopamine D1 receptor actions in layerV–VI rat prefrontal cortex neurons in vitro: Modulation of dendriticso-matic signal integration. J Neurosci 16:1922–1935.

22. Aghajanian GK, Marek GJ (1997): Serotonin induces excitatory postsyn-
aptic potentials in apical dendrites of neocortical pyramidal cells. Neu-ropharmacology 36:589 –599.

3. Henze DA, González-Burgos GR, Urban NN, Lewis DA, Barrionuevo G(2000): Dopamine increases excitability of pyramidal neurons in pri-mate prefrontal cortex. J Neurophysiol 84:2799 –2809.

4. Lambe EK, Goldman-Rakic PS, Aghajanian GK (2000): Serotonin inducesEPSCs preferentially in layer V pyramidal neurons of the frontal cortex inthe rat. Cereb Cortex 10:974 –980.

5. Thurley K, Senn W, Lüscher HR (2008): Dopamine increases the gain ofthe input-output response of rat prefrontal pyramidal neurons. J Neuro-physiol 99:2985–2997.

6. Zhang ZW, Arsenault D (2005): Gain modulation by serotonin in pyrami-dal neurones of the rat prefrontal cortex. J Physiol 566:379 –394.

7. Araneda R, Andrade R (1991): 5-Hydroxytryptamine2 and 5-hydroxy-tryptamine 1A receptors mediate opposing responses on membraneexcitability in rat association cortex. Neuroscience 40:399 – 412.

8. Tanaka E, North RA (1993): Actions of 5-hydroxytryptamine on neuronsof the rat cingulate cortex. J Neurophysiol 69:1749 –1757.

9. O’Donnell P (2010): Adolescent maturation of cortical dopamine [pub-lished online ahead of print February 12]. Neurotox Res.

0. Zhang ZW (2003): Serotonin induces tonic firing in layer V pyramidalneurons of rat prefrontal cortex during postnatal development. J Neu-rosci 23:3373–3384.

1. Goodfellow NM, Benekareddy M, Vaidya VA, Lambe EK (2009): Layer.II/III of the prefrontal cortex: Inhibition by the serotonin 5-HT1A recep-tor in development and stress. J Neurosci 29:10094 –10103.

2. Béïque JC, Chapin-Penick EM, Mladenovic L, Andrade R (2004): Seroto-nergic facilitation of synaptic activity in the developing rat prefrontalcortex. J Physiol 556:739 –754.

3. Carr DB, Cooper DC, Ulrich SL, Spruston N, Surmeier DJ (2002): Serotoninreceptor activation inhibits sodium current and dendritic excitability inprefrontal cortex via a protein kinase C-dependent mechanism. J Neu-rosci 22:6846 – 6855.

4. Martín-Ruiz R, Ugedo L, Honrubia MA, Mengod G, Artigas F (2001):Control of serotonergic neurons in rat brain by dopaminergic receptorsoutside the dorsal raphe nucleus. J Neurochem 77:762–775.

5. Lidow MS, Goldman-Rakic PS, Gallager DW, Rakic P (1991): Distributionof dopaminergic receptors in the primate cerebral cortex: Quantitativeautoradiographic analysis using [3H]raclopride, [3H]spiperone and[3H]SCH23390. Neuroscience 40:657– 671.

6. Goldman-Rakic PS, Lidow MS, Smiley JF, Williams MS (1992): The anat-omy of dopamine in monkey and human prefrontal cortex. J NeuralTransm Suppl 36:163–177.

7. Gaspar P, Bloch B, Le Moine C (1995): D1 and D2 receptor gene expres-sion in the rat frontal cortex: Cellular localization in different classes ofefferent neurons. Eur J Neurosci 7:1050 –1063.

8. Zhang ZW, Burke MW, Calakos N, Beaulieu JM, Vaucher E (2010): Confo-cal analysis of cholinergic and dopaminergic inputs pyramidal cells inthe prefrontal cortex of rodents. Front Neuroanat 4:21.

9. Seamans JK, Gorelova N, Durstewitz D, Yang CR (2001): Bidirectionaldopamine modulation of GABAergic inhibition in prefrontal corticalpyramidal neurons. J Neurosci 21:3628 –3638.

0. Trantham-Davidson H, Neely LC, Lavin A, Seamans JK (2004): Mecha-nisms underlying differential D1 versus D2 dopamine receptor regula-tion of inhibition in prefrontal cortex. J Neurosci 24:10652–10659.

1. Zheng P, Zhang XX, Bunney BS, Shi WX (1999): Opposite modulation ofcortical N-methyl-D-aspartate receptor-mediated responses by low andhigh concentrations of dopamine. Neuroscience 91:527–535.

2. Gulledge AT, Jaffe DB (2001): Multiple effects of dopamine on layer Vpyramidal cell excitability in rat prefrontal cortex. J Neurophysiol 86:586 –595.

3. Cai X, Gu Z, Zhong P, Ren Y, Yan Z (2002): Serotonin 5-HT1A receptorsregulate AMPA receptor channels through inhibiting Ca2/calmodu-lin-dependent kinase II in prefrontal cortical pyramidal neurons. J BiolChem 277:36553–36562.

4. Azmitia EC, Gannon PJ, Kheck NM, Whitaker-Azmitia PM (1996): Cellularlocalization of the 5-HT1A receptor in primate brain neurons and glialcells. Neuropsychopharmacology 14:35– 46.

5. Jakab RL, Goldman-Rakic PS (1998): 5-hydroxytryptamine 2A serotoninreceptors in the primate cerebral cortex: Possible site of action of hallu-cinogenic and antipsychotic drugs in pyramidal cell apical dendrites.Proc Natl Acad Sci U S A 95:735–740.

6. Aghajanian GK, Marek GJ (1999): Serotonin, via 5-HT2A receptors, in-
creases EPSCs in layer V pyramidal cells of prefrontal cortex by an asyn-chronous mode of glutamate release. Brain Res 825:161–171.

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5

6

6

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6

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47. Yang CR, Seamans JK, Gorelova N (1996): Electrophysiological and mor-phological properties of layers V-VI principal pyramidal cells in rat pre-frontal cortex in vitro. J Neurosci 16:1904 –21.

48. Kole MH, Bräuer AU, Stuart GJ (2007): Inherited cortical HCN1 channelloss amplifies dendritic calcium electrogenesis and burst firing in a ratabsence epilepsy model. J Physiol 578:507–525.

49. Arnsten AF, Paspalas CD, Gamo NJ, Yang Y, Wang M (2010): Dynamic NetworkConnectivity: A new form of neuroplasticity. Trends Cogn Sci 14:365–375.

50. Gao WJ, Goldman-Rakic PS (2003): Selective modulation of excitatoryand inhibitory microcircuits by dopamine. Proc Natl Acad Sci U S A 100:2836 –2841.

51. Allen PP, Cleare AJ, Lee F, Fusar-Poli P, Tunstall N, Fu CH, et al. (2006):Effect of acute tryptophan depletion on pre-frontal engagement. Psy-chopharmacology 187:486 – 497.

52. Zahrt J, Taylor JR, Mathew RG, Arnsten AF (1997): Supranormal stimula-tion of D1 dopamine receptors in the rodent prefrontal cortex impairsspatial working memory performance. J Neurosci 17:8528 – 8535.

53. Floresco SB, Phillips AG (2001): Delay-dependent modulation of mem-ory retrieval by infusion of a dopamine D1 agonist into the rat medialprefrontal cortex. Behav Neurosci 115:934 –939.

54. Winterer G, Weinberger DR (2004): Genes, dopamine and cortical signal-to-noise ratio in schizophrenia. Trends Neurosci 27:683– 690.

55. Williams GV, Rao SG, Goldman-Rakic PS (2002): The physiological role of5-HT2A receptors in working memory. J Neurosci 22:2843–2854.

56. Vijayraghavan S, Wang M, Birnbaum SG, Williams GV, Arnsten AF (2007):Inverted-U dopamine D1 receptor actions on prefrontal neurons en-gaged in working memory. Nat Neurosci 10:376 –384.

57. Sawaguchi T (2001): The effects of dopamine and its antagonists on
directional delay-period activity of prefrontal neurons in monkeys
during an oculomotor delayed-response task. Neurosci Res 41:115–128.

8. Lapish CC, Durstewitz D, Chandler LJ, Seamans JK (2008): Successfulchoice behavior is associated with distinct and coherent networkstates in anterior cingulate cortex. Proc Natl Acad Sci U S A 105:11963–11968.

9. Phillips AG, Ahn S, Floresco SB (2004): Magnitude of dopamine release inmedial prefrontal cortex predicts accuracy of memory on a delayedresponse task. J Neurosci 24:547–553.

0. Durstewitz D, Seamans JK, Sejnowski TJ (2000): Dopamine-mediatedstabilization of delay-period activity in a network model of prefrontalcortex. J Neurophysiol 83:1733–1750.

1. Durstewitz D, Vittoz NM, Floresco SB, Seamans JK (2010): Abrupt transi-tions between prefrontal neural ensemble states accompany behav-ioral transitions during rule learning. Neuron 66:438 – 448.

2. Robbins TW, Roberts AC (2007): Differential regulation of fronto-execu-tive function by the monoamines and acetylcholine. Cereb Cortex17(suppl 1):i151–i160.

3. Floresco SB, Zhang Y, Enomoto T (2009): Neural circuits subservingbehavioral flexibility and their relevance to schizophrenia. Behav BrainRes 204:396 – 409.

4. Mendlin A, Martín FJ, Jacobs BL (1999): Dopaminergic input is re-quired for increases in serotonin output produced by behavioralactivation: An in vivo microdialysis study in rat forebrain. Neurosci-ence 93:897–905.

5. Li SX, Perry KW, Wong DT (2002): Influence of fluoxetine on the ability ofbupropion to modulate extracellular dopamine and norepinephrineconcentrations in three mesocorticolimbic areas of rats. Neuropharma-
cology 42:181–190.

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