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Serotoninergic innervation of nonprincipal cells in the cerebral cortex of the lizard Podarcis hispanica
Author(s) -
MartínezGuijarro F. J.,
BlascoIbáñez J. M.,
Freund T. F.
Publication year - 1994
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.903430405
Subject(s) - serotonergic , biology , neuroscience , parvalbumin , gabaergic , hippocampal formation , inhibitory postsynaptic potential , hippocampus , cerebral cortex , neurotransmission , serotonin , receptor , biochemistry
Abstract The mechanism of serotoninergic transmission in the neo‐ and archicortex of mammals kis complex, including both synaptic and nonsynaptic components, direct actions on principal cells, and indirect effects mediated by GABAergic interneurons. Here we studied the termination pattern and synaptic organization of the serotoninergic afferents in the cerebral cortex of the lizard, Podarcis hispanica , which is considered to correspond in part to the mammalian hippocampal formation, with the aim of unraveling basic, phylogenetically preserved rules in the connectivity of this pathway. We demonstrate that serotoninergic afferents, visualized by immunostaining for serotonin itself, establish multiple synaptic contacts with different subpopulations of nonprincipal cells containing parvalbumin, neuropeptide Y, and opioid peptides. The former two subpopulations contain GABA, whereas the opioid‐ immunoreactive neurons are most likely GABA‐negative cells. Evidence is provided at the electron microscopic level that serotonin‐immunoreactive varicosities establish conventional asymmetric synaptic contacts with their nonprincipal targets, but nonsynaptic varicosities also exist. We conclude that, similarly to mammals, a selective synaptic innervation of nonprincipal, possibly inhibitory, neurons is among the mechanisms of serotoninergic modulation of cerebral cortical activity in the lizard. © 1994 Wiley‐Liss, Inc.