[Fast modulation of glutamate and GABA receptor--mediate electrophysiological responses by glucocorticoid]

Fast modulation by glucocorticoid on gluatmate and GABA receptor-mediated electrophysiological responses was investigated by extracellular iontophoresis and intracellular techniques in rat hypothalamic brain slices and guinea pig coeliac ganglion preparations respectively. The results were as follows: Glucocorticoid inhibited the glutamate receptor-mediated excitatory response and potentiated the GABA receptor-mediated inhibitory response within 5 min after perfusion. All these responses are reversible after removal of the glucocorticoid. Low Ca2+ high Mg2+ medium was ineffective to block the fast modulatory effects of glucocorticoid on the gluatmate and GABA receptor-mediated responses. It appears that the latter responses are mediated through some non-genomic mechanism without an involvement of synaptic circuitry.