title: Age-Dependent Switch of the Role of Serotonergic 5-HT1A Receptors in Gating Long-Term Potentiation in Rat Visual Cortex In Vivo.
abstract: The rodent primary visual cortex (V1) is densely innervated by serotonergic axons and previous in vitro work has shown that serotonin (5-HT) can modulate plasticity (e.g., long-term potentiation (LTP)) at V1 synapses. However, little work has examined the effects of 5-HT on LTP under in vivo conditions. We examined the role of 5-HT on LTP in V1 elicited by theta burst stimulation (TBS) of the lateral geniculate nucleus in urethane-anesthetized (adult and juvenile) rats. Thalamic TBS consistently induced potentiation of field postsynaptic potentials (fPSPs) recorded in V1. While 5-HT application (0.1-10 mM) itself did not alter LTP levels, the broad-acting 5-HT receptor antagonists methiothepin (1 mM) resulted in a clear facilitation of LTP in adult animals, an effect that was mimicked by the selective 5-HT1A receptor antagonist WAY 100635 (1 mM). Interestingly, in juvenile rats, WAY 100635 application inhibited LTP, indicative of an age-dependent switch in the role of 5-HT1A receptors in gating V1 plasticity. Analyses of spontaneous electrocorticographic (ECoG) activity in V1 indicated that the antagonist-induced LTP enhancement was not related to systematic changes in oscillatory activity in V1. Together, these data suggest a facilitating role of 5-HT1A receptor activation on LTP in the juvenile V1, which switches to a tonic, inhibitory influence in adulthood.
authors.affiliation: Center for Neuroscience Studies, Queen's University, Kingston, ON, Canada K7L 3N6.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Gagolewicz
authors.affiliation: Center for Neuroscience Studies, Queen's University, Kingston, ON, Canada K7L 3N6; Department of Psychology, Queen's University, Kingston, ON, Canada K7L 3N6.
authors.forename: Hans C
authors.initials: HC
authors.lastname: Dringenberg
mesh_terms: D000367:Age Factors; D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008719:Methiothepin / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D044282:Receptor, Serotonin, 5-HT1A / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000378:metabolism; D014793:Visual Cortex / Q000187:drug effects / Q000378:metabolism*
chemical_list: D010879:Piperazines; D011725:Pyridines; D012702:Serotonin Antagonists; D044282:Receptor, Serotonin, 5-HT1A; D012701:Serotonin; D008719:Methiothepin; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide