the amazing brain webinar series: select topics in ... webinars/nicotine and...introductions . carol...

The Amazing Brain Webinar Series: Select Topics in Neuroscience and Child

Development for the Clinician

Part IV – Nicotine and Cortical Development

Marina Picciotto, PhD

Jointly sponsored by the Association of University Centers on Disabilities, the Maternal and Child Health Bureau/Health Resources and Services Administration and Yale School of Medicine, Section of Developmental-Behavioral Pediatrics

Webinar Overview

• Webinar Recording – Visit www.aucd.org/webinars

• Q & A – Please submit your questions throughout the webinar via

the “question box” on your webinar dashboard. Questions will be answered following the presentation.

• Survey – Please complete the short survey at the end of the webinar!

http://www.aucd.org/webinars

Introductions

Carol Weitzman, MD, Associate Professor of Pediatrics and the Child Study Center, Yale School of Medicine

Marina Picciotto, PhD, Charles B.G. Murphy Professor, Departments of Psychiatry, Neurobiology and Pharmacology, Yale School of Medicine

Marina Picciotto, Charles B.G. Murphy Professor Depts. of Psychiatry, Neurobiology & Pharmacology Yale University School of Medicine

Developmental effects of nicotine and nicotinic acetylcholine receptors on circuits involved in passive avoidance learning

Smoking and Pregnancy

• 10.7-12.4% of US pregnant women are smokers

(Martin, J.A. et al. (2007) Natl. Vit. Stat. Rep. (56) pp1-104)

• Underestimate due to maternal self-report (England, L.J. et al. (2007) Nicotine Tob. Res. (10) pp1005-1013)

(Warland, J. et al. (2010) Midwifery Epub)

• Relapse and intermittent smoking in pregnancy

(Warland, J. et al. (2010) Midwifery Epub)

Smoking and Pregnancy • Persistent mental health effects in

exposed offspring – ADHD – Conduct Disorder – Antisocial behavior – Substance abuse – Psychotic-like symptoms / Psychiatric morbidity – Cognitive and attentional deficits

(Fried, P. et al. (1997) Neurotoxicol. Teratol. (19) pp171-183) (Button, T.M.M. et al. (2007) Early Hum. Dev. (83) pp727-732)

(Jacobsen, L.K. et al. (2007) Neuropsychopharm. (32) pp2453-2464) (Zammit, S. et al. (2009) Br. J. Psychiatr. (195) pp294-300)

(Ekblad, M. et al. (2010) Arch. Gen. Psych. (67) pp841-849)

• Does developmental tobacco exposure cause ADD?

• Which tobacco component is responsible?

• What is the underlying mechanism?

Developmental effects of smoking

nAChRs α4

β2 β2

β2 α4

α4 β2

α4 β2

α4

α4 α5

β2 β2

α4

α7 α7

α7 α7

α7

• Ligand gated ion channels • 12 potential neuronal subunits • Heteromeric vs. homomeric • Biophysical and pharmacological parameters affected by

subunit composition • Widespread and early expression in CNS

(Gotti, C. et al. (2006) TiPS (27) pp482- 491) (Gotti, C. et al. (2007) Biochem. Pharmacol. (74) pp1102-1111)

(Collins, A.C. et al. (2009) Handbook Expt. Pharmacol. (192) pp85-112)

Developmental effects of nicotine

• nAChR stimulation potentiates LTP at glutamatergic synapses in sensory cortex and thalamus

• Nicotine accelerates maturation of GABA and glutamate synapses

(Metherate; Berg)

Neurobiological studies:

Nicotinic acetylcholine receptors (nAChRs) are the primary molecular targets for nicotine

neuronal type nicotinic receptors

α 3

α 3

β 4 α 3

β 4 α 4

α 6

β 2 β 3

β 2

α 7

α 7

α 7 α 7

α 7

muscle type nicotinic receptor

α β γ

α

δ

1

1

Mouse model of developmental nicotine exposure

• Nicotine-treated drinking water • Dam drinks throughout pregnancy

• Nicotine levels vary and are low during sleep • Pups are exposed to nicotine that crosses the

placenta or is delivered through mother’s milk

Testing Time entry to dark chamber

The image part with relationship ID rId3 was not found in the file.

dark compartment

light compartment


- Dams 200 ug/ml nicotine in drinking water - Offspring weaned on water (3 - 4 weeks), tested as adults (3 - 5 months).

Nicotine during development results in hypersensitive passive avoidance in adulthood

Tim

e to

ent

er d

ark

cham

ber (

sec)

NIC

E1 Birth P21 P90

NIC PA

King et al, J. Neuroscience, 2003

.

training testing

120

100

80

60

40

20

0 wildtype knockout

Constitutive β2 subunit knockout results in hypersensitive passive avoidance learning

Picciotto et al, Nature, 1995

Tim

e to

ent

er d

ark

(sec

)

Testing Time entry to dark chamber


dark light compartment


Questions to be answered:

•Where in the brain is this happening?

•When during development are nAChRs necessary for this effect?

•Does this have relevance for human beings?

Inducible region specific expression

Temporal-control of gene expression

β2 +/-

β2 -/-

β2 tr(CT)

β2 tr(VN)

β2 tr(VTA)

β2 tr(FB) (CamKII-tTA)

Region-specific β2 nAChR expression

King et al, J. Neuroscience, 2003

wildtype β2 knockout transgenic Nicotine binding

in situ hybridization

thalamus

cortex Rubidium efflux

Thalamic Relay Neuron

Sensory Input

IV

V

VI

Thalamic Reticular Neuron

Adapted from: Miyata, M. (2007) Neurosci. Res. (59) pp377-382

Reichova, I. and Sherman, S.M. (2004) J. Neurophysiol. (92) pp2185-2197

Cortico-Thalamic Circuitry


Sensory Input

IV

V

VI




Cortico-Thalamic Circuitry a7 modulated synapse

(Metherate)


Sensory Input

IV

V

VI





β2* modulated synapse?

Corticothalamic expression of β2 nAChRs rescues adult passive avoidance

King et al, J. Neurosci., 2003

Effect of developmental nicotine on PA depends on corticothalamic β2* nAChRs

mean time to enter

dark chamber

(sec)

0

50

100

150

200

250

300

Saline Nicotine Saline Nicotine KO CT Transgenics

Tim

e to

en

ter

the

dar

k ch

amb

er (

sec)

Train Test

***

Heath et al, Neuropsychopharmacology, 2010

PA

E1 Birth P21 P90

NIC NIC

Other nAChR subunits expressed by corticothalamic neurons

• α5:

α5 In-situ hybridization


α5 nAChR expression: functional consequences

• α5: is an accessory subunit – α4β2α5 nAChRs exhibit higher

conductance and faster inactivation (Ramirez-Latorre, J. et al. (1996) Nature (380) pp347-351)

– α4β2α5 nAChRs respond differently to intracellular Ca2+

• ↓ p(open) + open duration • ↑ inter burst interval

(Girod, R. et al. (1999) Ann. NY Acad. Sci. (868) pp578-590)

α5 nAChR expression: functional consequences

• α5 nAChR subunit KO mice: – Relatively indistinguishable from WTs – Nicotine-induced seizure resistance

(Salas, R. et al. (2003) Mol. Pharmacol. (63) pp1059-1066)

• Decreased function in corticothalamic terminal nAChRs – Thalamic synaptosomal 86Rb+ efflux

(Brown, R.W. et al. (2007) J. Neurochem. (103) pp204-215)

α5 knockout mice show partial hypersensitivity in passive avoidance


Corticothalamic mice show rescued α4/β2/α5 nAChRs




Sensory Input

IV

V

VI




α4β2α5 modulated synapse

Perinatal nicotine

Temporally-controlled gene expression


β2* nAChRs in corticothalamic neurons during development rescue PA

mean time to enter

dark chamber

(sec)


The β2 nAChR transgene is expressed in corticothalamic efferents after P7


Mouse model of developmental nicotine exposure

• Nicotine-treated drinking water • Dam drinks throughout pregnancy

• Cross foster to naïve dam = prenatal • Keep pups with dam = pre- and

postnatal • Cross foster to nicotine dam = postnatal

Nicotine affects passive avoidance when administered only posnatally

0

40

80

120

160

200

240

280

320

Sac-Sac Sac-Nic Nic-Sac Nic-Nic

train test

nicotine Saccharin

birth weaning conception Day -19.5 Day 0 Day 21

* *

Tim

e to

ent

er d

ark

cham

ber (

sec)

PA

E1 Birth P21 P90

SAC NIC NIC SAC


Jacobsen et al, J Neuroscience, 2007

Developmental smoke exposure alters white matter maturation in internal capsule

Myelinated Optic Nerve

What we think is happening

Corticothalamic Glutamatergic Projection neuron

Cholinergic afferent from hind brain

Somatosensory neuron

Thalamocortical relay cell

Glutamatergic projection back to cortex

ACh X

Summary

• Both perinatal nicotine exposure and β2* nACHR KO result in hypersensitive passive avoidance in adulthood

• Expression in corticothalamic efferents rescues this defect in KO mice and restores nicotine sensitivity

• nAChR signaling appears to be critical for maturation of corticothalamic glutamate synapses in mice and humans

Steve Buka J-P Changeux Al Collins Sharon Grady Cecelia Gotti Leslie Jacobsen

Current lab members

Sam Blakeman Cali Calarco Emily Einstein Giana Fote Nadia Gavrilova Shefali Jain Yonwoo Jung Yann Mineur Samantha Sheppard Seth Taylor

Past lab members involved in these studies:

Christopher Heath Postdoctoral Fellow Cambridge University Sarah King Lecturer University of Sussex

NIDA

NIMH

Michael Marks Eric Nestler Tony George Stephanie O’Malley Julie Staley Michele Zoli

Collaborators

TTURC

NARSAD

Funding

Q & A

• Ask a question! – Type your question in the “question box” on your webinar

dashboard.

– The moderator will read the question.

Thank You!

• Questions about the webinar? – Email Tory Christensen([email protected])

Please take a few minutes to complete the survey!

mailto:[email protected]

the amazing brain webinar series: select topics in ... webinars/nicotine and...introductions . carol...

Documents