dopamine in male sexual behavior elaine m. hull the florida state university psychology department...
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Dopamine in Male Sexual Behavior
Elaine M. Hull
The Florida State University
Psychology Department & Neuroscience Program
Neural circuits regulating sexual behaviorNeural circuits regulating sexual behavior
OB
MeA
MPOA
NAc
BST
VTA
Brain Stem
CTF
Neural circuits regulating sexual behaviorNeural circuits regulating sexual behavior
OB
MeA
MPOA
NAc
BST
VTA
Brain Stem
CTF
Neural circuits regulating sexual behaviorNeural circuits regulating sexual behavior
OB
MeA
MPOA
NAc
BST
VTA
Brain Stem
CTF
Neural circuits regulating sexual behaviorNeural circuits regulating sexual behavior
OB
MeA
MPOA
NAc
BST
VTA
Brain Stem
CTF
Neural circuits regulating sexual behaviorNeural circuits regulating sexual behavior
OB
MeA
MPOA
NAc
BST
VTA
Brain Stem
CTF
Our lab has focused on the medial preoptic area, which contains A14 periventricular DA neurons. It is the main integrative area for male sexual behavior in all vertebrate species.
Model for MPOA dopamine’s influence on male sexual behavior
Is dopamine released in the MPOA during copulation?
Gonadally intact males and T-treated castrates had increased extracellular DA during pre-exposure to a female and during copulation. Vehicle-treated 1-week castrates that copulated also showed DA increases, but those that did not copulate did not show the DA increase.
What elicits the MPOA DA release?
Large lesions of the amygdala abolished copulation, which was restored by
apomorphine in the MPOA.
Smaller lesions of the MeA impaired, but did not abolish mating.
Basal DA levels in the MPOA were normal, but
the DA response to the female was abolished.
Chemical stimulation of the MeA mimicked the MPOA DA response to a female.
Therefore, normal basal DA in the MPOA is sufficient for suboptimal copulation. The DA increase in response to a female facilitates
mating and is mediated by input from the MeA.
• But there are no DA neurons in the MeA. What elicits the DA increase?
Glutamatergic axons from the MeA and BNST to MPOA
• Juan Dominguez, my former post-doc, showed that a few axons from the MeA, and numerous axons from the BNST, ended in the MPOA and contained glutamate.
Is glutamate released in the MPOA before and during mating?
Sample
BL PRE COP EJAC PEI POST
Glu
tam
ate
% c
han
ge
0
100
200
300
400**
*
Sexual activity increases glutamate in the MPOA of male rats.
Using 2 min microdialysis samples
Samples
BL UPTKi PRE COP EJAC PEI POST
Glu
tam
ate
% c
han
ge
0
100
200
300
400ACSFUPTKi
0
100
200
300
400
0
100
200
300
400
500
600
EJACULATIONFREQUENCY
EJACULATIONLATENCY (sec) PEI (sec)
Reverse dialysis of glutamate uptake inhibitors into the MPOA increased glutamate levels and facilitated mating.
**
0
1
2
3
4
5 *** *
Therefore, glutamate is released in the MPOA during copulation, and it facilitates mating.
• Does glutamate also affect MPOA DA levels?
Sample (6 min)
DO
PA
C %
C
HA
NG
EH
VA
%
CH
AN
GE
Sample (6 min)
Exogenous glutamate in the MPOA increased DA levels, but decreased DOPAC and HVA
DA
%
CH
AN
GE
Nitric oxide has been reported to inhibit DA transport and increase DA levels in the striatum.
• Could NO explain our results?
L-NAME blocked the glutamate-evoked DA release and the decreases in
DOPAC and HVA.
DA
%
CH
AN
GE
Sample (6 min)
DO
PA
C %
C
HA
NG
EH
VA
%
CH
AN
GE
Sample (6 min)
Metabolite levels were lower for animals receiving glutamate alone compared with those receiving glutamate+ L-NAME.
Exogenous glutamate in the MPOA increased DA levels, but inhibited
metabolites: Role for NO?POSSIBLE EXPLANATIONS FOR
THIS EFFECT:
1. Glutamate induces exocytocis of DA
2. Glutamate binds NMDA receptors, which allows for Ca2+ influx and induces NO production in NOS- containing cells.
a) Increased NO may inhibit DA uptake in neighboring terminals, prolonging DA’s effects & decreasing DA catabolism.
b) Increased NO might also increase extracellular DA by inducing vesicular leakage.
MPOA dopamine release during copulationdepends on nitric oxide
L-NAME blocked mating-induced DA release in the MPOA.
Microinjection of L-NAME into the MPOA impaired copulation in sexually naïve (A) and experienced (B) males.
A B
Sexually Experienced Males
1. Show increased preference for being with a receptive female.
Sexually Experienced Males
1. Increased preference for being with a receptive female.
2. Require less time and stimulation to achieve ejaculation.
Sexually Experienced Males
1. Increased preference for being with a receptive female.
2. Require less time and stimulation to achieve ejaculation.
3. Require less time to resume copulation after ejaculating.
Sexually Experienced Males
1. Increased preference for being with a receptive female.
2. Require less time and stimulation to achieve ejaculation.
3. Require less time to resume copulation after ejaculating.
4. Are more resistant to sexual impairments due to castration, brain damage, or stress.
Sexually Experienced Males
1. Increased preference for being with a receptive female
2. Require less time and stimulation to achieve ejaculation
3. Require less time to resume copulation after ejaculating
4. Are more resistant to sexual impairments due to castration, brain damage, or stress
Is the MPOA implicated?Is the MPOA implicated?
Stronger Activation of the MPOA in Sexually Experienced Males
Sexually experienced males had more Fos-ir in the MPOA resulting from mating to one ejaculation, than did naïve males that mated for the first time.
First Experience
Repeated Experience
Does NOS in the MPOA contribute to exposure-induced enhancement of mating?
L-NAME administration before each of seven non-copulatory exposures to an estrous female blocked exposure-induced enhancements on the drug-free test day. (Preliminary data suggest that a D1 antagonist has similar effects.)
NNS NS ENS ES
% NOS w/NR1P
erce
ntag
e
0
25
50
75
100
Total NOS
# Cel
ls
NNS NS ENS ES0
20
40
60
80
* **
Sexual experience increases NOS-ir in the MPOA of male
rats
NOS
NMDAR1
Overlay
Nearly all cells containing NOS also contained NMDA receptors. Sexual experience increased the number of NOS-ir cells in MPOA.
Sexually Naïveand Mated
(NM)
SexuallyExperienced
and Not Mated(EC)
Sexually Naïveand Not Mated
(NC)
SexuallyExperiencedand Mated
(EM)M
EA
N D
EN
SIT
Y
(PIX
ELS
)
0
50
100
150
NC NM EC EM
* *
*
Sexual experience increases NOS protein concentration in the MPOA of male rats
A major means of activating NOS is via NMDA glutamate receptors. Does an NMDA antagonist in the MPOA also impair sexual sensitization?
Blocking NMDA receptors in the MPOA impaired sexual sensitization.
Microinjecting MK-801 before each noncopulatory exposures to an estrous female impaired exposure-induced enhancements of:
1. number of mounts
0
2
4
6
8
10
12
14
16
MO
UN
TS
Saline
MK801
Naive*
0
2
4
6
8
10
12
14
16
18
INT
RO
MIS
SIO
NS
Saline
MK801
Naive
Blocking NMDA receptors in the MPOA impaired sexual sensitization.
Microinjecting MK-801 prior to repeated noncopulatory exposures to an estrous female impaired experience-induced enhancements on:
1. number of mounts2. number of intromissions
*
0
0.5
1
1.5
2
2.5
EJA
CU
LA
TIO
NS
Saline
MK801
Naive
Blocking NMDA receptors in the MPOA impaired sexual sensitization.
Microinjecting MK-801 prior to repeated noncopulatory exposures to an estrous female impaired experience-induced enhancements on:
1. number of mounts2. number of intromissions3. number of ejaculations
*
• What intracellular messenger mediates NO’s effects?
Inhibition of guanylyl cyclase blocked effects of the NO donor (sodium nitroprusside).
Cyclic GMP mediates NO’s facilitation of DA release in the MPOA
Cyclic GMP mediates NO’s facilitation of DA release in the MPOA
Inhibition of NOS did not affect facilitation by cGMP analog, because cGMP is downstream of NOS.
Summary
NOS
NM
DA
r
Glutamate
Dopamine
Sexual stimulation
NO
Summary
NOS
NM
DA
r
Glutamate
Dopamine
Sexual stimulation
NO
Summary
NOS
NM
DA
r
Glutamate
Dopamine
Sexual stimulation
(Higher NOSw/ experience)
Postscript: Orexin/hypocretin increases mesolimbic DA activity and facilitates
copulation
Copulation increased Fos-ir in orexin-containing
neurons of perifornical LH.
Double-labeled cells in Non-copulating males
Double-labeled cells in copulating males
Castration decreased
orexin-containing cells; E2
restored them.
Orexin (.014 nmol) in the VTA increased firing rates
of DA neurons.
Orexin (1.4 nmol) in the VTA increased cells per track,
but not firing rates.
Orexin (140 nmol) in the VTA decreased cells per track, probably due to
depolarization block, an effect reversed by
autoreceptor stimulation by
systemic apomorphine.
Red orexin-containing axons end near green TH-containing neurons that are activated (Fos-ir, black) by
copulation.
• Estrogen receptor-containing cells in the MPOA, BNST, and LHA orexin-containing cells in the LHA. Axons from those cells depolarize DA-ergic cells in the VTA and, perhaps, the MPOA. Microinjection of orexin into the MPOA facilitates male sexual behavior (Gulia et al., 2003). 5-HT is released in the LHA at the time of ejaculation and inhibits mating. It also decreases DA release in the NAc (Lorrain et al., 1999) and hyperpolarizes orexin neurons (Li et al., 2002).
Acknowledgments Acknowledgments
K02-MH001714R01-MH040826
Former and Present Lab Members:Bradley Lown, Ph.D Linda Rosselli-Austin, Ph.D Rosemary D’Agostino, Ph.D Deborah Kleese Edelstein, Ph.D Mary Solanto, Ph.D Richard Thomas, Ph.D J. Ken Nishita, Ph.D Daniel Bitran, Ph.D Elizabeth A. Pehek, Ph.D Linda C. Band, Ph.DTerrence Bazzett, Ph.D Vincent P. Markowski, Ph.D Robert C. Eaton, Ph.D Jason Moses, Ph.DLeslie Matuszewich, Ph.D Jianfang Du, Ph.D Susan K. Putnam, Ph.D Jon V. Riolo, Ph.DKatie Grausam
Juan Dominguez, Ph.D
Mario Gil
Gwen Lagoda
Lucy Lumley, Ph.D
Daniel Lorrain, Ph.D
Satoru Sato, Ph.D
Anna Vigdorchik
John Muschamp, Ph.D
Harvey Rattus
SNP and 8-Br-cGMP increase DA levels in the MPOA of DHT-treated castrates.
However, SNP was somewhat more effective.
Only SNP increased DOPAC in DHT-Treated Castrates
Only SNP into the MPOA facilitated sexual behavior in DHT treated castrates
0.00
10.00
20.00
30.00
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90.00
100.00
Control 8-Br-cGMP SNP
Percent that Displayed Mounts
PE
RC
EN
T
*
Only SNP into the MPOA facilitates sexual behavior in DHT treated castrates
Control 8-Br-cGMP SNP
Percent that Displayed Intromissions
PE
RC
EN
T
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
*
Only SNP into the MPOA facilitates sexual behavior in DHT treated castrates
Control 8-Br-cGMP SNP
Percent that Displayed Ejaculations
PE
RC
EN
T
0.00
10.00
20.00
30.00
40.00
50.00
60.00
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100.00
*
PEI (Sec)
100 200 300 400 500 600
Glu
tam
ate
% d
ecre
ase
0
100
200
300
400
500
600
Sample
BL PRE COP EJAC PEI POST
Glu
tam
ate
% c
han
ge
0
100
200
300
400
**
*
Magnitude of decrease in glutamate after ejaculation correlates with post-ejaculatory
interval.
Blocking D1 Receptors Attenuated Activation of MPOA During Initial
Experience
Males receiving a D1 antagonist had less Fos-ir in the MPOA after their first sexual experience, than did males receiving vehicle.
Vehicle
D1 Antagonist