Conditional expression in corticothalamic efferents reveals a developmental role for nicotinic acetylcholine receptors in modulation of passive avoidance behavior.
Prenatal nicotine exposure has been linked to attention deficit hyperactivity disorder and cognitive impairment, but the sites of action for these effects of nicotine are still under investigation. High-affinity nicotinic acetylcholine receptors (nAChRs) contain the beta2 subunit and modulate passive avoidance (PA) learning in mice. Using an inducible, tetracycline-regulated transgenic system, we generated lines of mice with expression of high-affinity nicotinic receptors restored in specific neuronal populations. One line of mice shows functional beta2 subunit-containing nAChRs localized exclusively in corticothalamic efferents. Functional, presynaptic nAChRs are present in the thalamus of these mice as detected by nicotine-elicited rubidium efflux assays from synaptosomes. Knock-out mice lacking high-affinity nAChRs show elevated baseline PA learning, whereas normal baseline PA behavior is restored in mice with corticothalamic expression of these nAChRs. In contrast, nicotine can enhance PA learning in adult wild-type animals but not in corticothalamic-expressing transgenic mice. When these transgenic mice are treated with doxycycline in adulthood to switch off nAChR expression, baseline PA is maintained even after transgene expression is abolished. These data suggest that high-affinity nAChRs expressed on corticothalamic neurons during development are critical for baseline PA performance and provide a potential neuroanatomical substrate for changes induced by prenatal nicotine exposure leading to long-term behavioral and cognitive deficits.
King
Sarah L
SL
Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut 06508, USA.
Marks
Michael J
MJ
Grady
Sharon R
SR
Caldarone
Barbara J
BJ
Koren
Andrei O
AO
Mukhin
Alexey G
AG
Collins
Allan C
AC
Picciotto
Marina R
MR
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology*; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001667:Binding, Competitive; D002540:Cerebral Cortex / Q000502:physiology*; D004597:Electroshock; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009476:Neurons, Efferent / Q000187:drug effects / Q000502:physiology*; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000493:pharmacokinetics; D017729:Presynaptic Terminals / Q000378:metabolism; D011978:Receptors, Nicotinic / Q000235:genetics / Q000502:physiology*; D013752:Tetracycline / Q000494:pharmacology; D013788:Thalamus / Q000502:physiology*; D019076:Transgenes / Q000187:drug effects
D009538:Nicotine; D018722:Nicotinic Agonists; D011978:Receptors, Nicotinic; D013752:Tetracycline