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ELECTROPHYSICAL PROPERTIES, SYNAPTIC TRANSMISSION AND NEUROMODULATION IN SEROTONERGIC CAUDAL RAPHE NEURONS
Author(s) -
Li YuWen,
Bayliss Douglas A.
Publication year - 1998
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1998.tb02237.x
Subject(s) - serotonergic , neuroscience , excitatory postsynaptic potential , neurotransmission , raphe , glutamatergic , raphe nuclei , chemistry , neuromodulation , serotonin , biology , glutamate receptor , inhibitory postsynaptic potential , stimulation , receptor , biochemistry
SUMMARY 1. We studied electrophysiological properties, synaptic transmission and modulation by 5‐hydroxytryptamine (5‐HT) of caudal raphe neurons using whole‐cell recording in a neonatal rat brain slice preparation; recorded neurons were identified as serotonergic by post‐hoc immunohistochemical detection of tryptophan hydroxylase, the 5‐HT‐synthesizing enzyme. 2. Serotonergic neurons fired spontaneously (approximately 1 Hz), with maximal steady state firing rates of < 4 Hz. 5‐Hydroxytryptamine caused hyperpolarization and cessation of spike activity in these neurons by activating inwardly rectifying K + conductance via somatodendritic 5‐HT 1A receptors. 3. Unitary glutamatergic excitatory post‐synaptic potentials (EPSP) and currents (EPSC) were evoked in serotonergic neurons by local electrical stimulation. Evoked EPSC were potently inhibited by 5‐HT, an effect mediated by presynaptic 5‐HT IB receptors. 4. In conclusion, serotonergic caudal raphe neurons are spontaneously active in vitro; they receive prominent glutamatergic synaptic inputs. 5‐Hydroxytryptamine regulates serotonergic neuronal activity of the caudal raphe by decreasing spontaneous activity via somatodendritic 5‐HT IA receptors and by inhibiting excitatory synaptic transmission onto these neurons via presynaptic 5‐HTIB receptors. These local modulatory mechanisms provide multiple levels of feedback autoregulation of serotonergic raphe neurons by 5‐HT.