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GABAergic transmission in the rat paraventricular nucleus of the hypothalamus is suppressed by corticosterone and stress
Author(s) -
Verkuyl J. Martin,
Karst Henk,
Joëls Marian
Publication year - 2005
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2004.03846.x
Subject(s) - corticosterone , parvocellular cell , gabaergic , medicine , endocrinology , inhibitory postsynaptic potential , hypothalamus , neuroactive steroid , chemistry , biology , hormone , neuroscience , gabaa receptor , receptor
Parvocellular neurons in the hypothalamic paraventricular nucleus receive hormonal inputs mediated by corticosterone as well as neuronal inputs, prominent among which is a GABAergic inhibitory projection. In the present study we examined the functional properties of this GABAergic innervation when corticosteroid levels fluctuate. Frequency, amplitude and kinetic properties of miniature inhibitory postsynaptic potentials (mIPSCs), mediated by γ amino butyric acid (GABA) were studied with whole cell recording in parvocellular neurons. Injection of a high dose of corticosterone in vivo suppressed the frequency but did not change the amplitude and kinetic properties of mIPSCs recorded 1–5 h later in vitro . Similar effects were observed after restraint stress. The corticosteroid actions do not require involvement of extrahypothalamic brain regions, because in vitro administration of 100 n m corticosterone (20 min) directly to a hypothalamic slice also suppressed the frequency of mIPSCs recorded several hours later. Corticosterone administration to hypothalamic slices from restraint rats did not result in stronger reduction of mIPSC frequency than either treatment alone, pointing to a common underlying mechanism. Paired pulse response inhibition was reduced by corticosterone, suggesting that the hormone decreases the release probability of GABA‐containing vesicles. Unlike neurosteroids, corticosterone induced no rapid effects on mIPSC properties. These results indicate that increases in glucocorticoid level due to stress can slowly but persistently inhibit the GABAergic tone on parvocellular hypothalamic neurons via a hitherto unknown local mechanism independent of limbic projections.