ISSN:
1460-9568
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Intracellular recordings were performed in area CA1 pyramidal cells of rat hippocampal slices to determine the effects of certain steroids on inhibitory postsynaptic potentials/currents (IPSP/Cs) mediated by GABAA receptors. Following application of the steroids 5α-pregnan-3α,21-diol-20-one (5α-THDOC), alphaxalone and 5β-pregnan-3α-ol-20-one (pregnanolone) hyperpolarizing PSPs developed into biphasic responses consisting of an early hyperpolarizing and a late depolarizing PSP sequence. Steroid-induced depolarizing PSPs could be elicited in the presence of antagonists to non-NMDA, NMDA, and GABAB receptors, indicating that these receptor types do not contribute significantly to the initiation of these responses. Depolarizing PSPs were completely blocked by both GABAA receptor antagonists bicuculline and t-butylbicyclophosphorothionat (TBPS) providing evidence for their mediation by GABAA receptors. The reversal potential of steroid-induced late inward PSCs, measured in single-electrode voltage clamp, was –29.9 ± 5.3 mV, whereas the early outward current, which corresponded to the early hyperpolarizing component of PSPs, reversed at –68.2 ± 1.5 mV. Depolarizing PSPs and late inward PSCs were sensitive to reduction of extracellular [HCO3–] and block of carbonic anhydrase by application of acetazolamide. The results suggest that certain neuroactive steroids can induce GABAA receptor-mediated depolarizing PSPs, which are dependent on HCO3–.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1460-9568.1998.00297.x
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