title: Hippocampal nicotinic cholinergic mechanisms mediate spontaneous alternation and fear during ontogenesis but not later in the rat.
abstract: Spontaneous alternation was examined in young rats following microinjections of antinicotinic agents into one of the 4 hippocampal sites: anterodorsal, or posteroventral dentate gyrus, hippocampal gyrus, or entorhinal cortex. In control and saline-injected animals, the alternation rate was shown to grow suddenly from 40 to 80% between days 15 and 17 (the adult level being 85-90%), to regress partly (to 55%) between days 20 and 30, and return to a near-adult level (75%) by day 40. Meanwhile fear responses to environment (defecation and vocalization) emerged between days 20 and 25, increased to a maximum until day 30, and returned to the typically low adult level by day 40. Injections of mecamylamine (5, 20 micrograms) or hexamethonium (5, 20 micrograms) into any of the 4 sites significantly reduced the rate of alternation from as early as day 10 on, but were no longer effective from day 30 on; on the other hand, they did not alter the level of defecation, but had a tendency to lower the level of vocalization on day 30 only. These results indicate that hippocampal nicotinic cholinergic mechanisms play a role in spontaneous alternation and appear to be involved in the control of one fear reaction (vocalization) until day 30.
authors.affiliation: Université Pierre et Marie Curie-C.N.R.S. UA 1199, Département de Neurophysiologie Comparée, Paris, France.
authors.forename: D
authors.initials: D
authors.lastname: Blozovski
authors.forename: C
authors.initials: C
authors.lastname: Hess
mesh_terms: D000375:Aging / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D002799:Cholinergic Fibers / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D005239:Fear / Q000502:physiology*; D005260:Female; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D006624:Hippocampus / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000502:physiology*
chemical_list: D006584:Hexamethonium Compounds; D011978:Receptors, Nicotinic; D018738:Hexamethonium; D008464:Mecamylamine