Oxytocin depresses spontaneous gamma-aminobutyric acid-ergic inhibitory postsynaptic currents in cultured mitral cells of the rat olfactory bulb by apresynaptic mechanism

Oxytocin (OT) modulation of synaptic transmission between olfactory bulb ne urones has been implicated in the induction of maternal behaviour, but the mechanism of action is unknown. We examined the action of OT on gamma-amino butyric acid(A) (GABA(A)) receptor-mediated spontaneous inhibitory postsyn aptic currents (sIPSCs) in cultured mitral/tufted (M/T) cells with the use of whole-cell patch-clamp recordings. OT reversibly reduced the frequency o f sIPSCs without affecting the amplitudes. The effect of OT on sIPSCs was m imicked by the OT receptor agonist [Thr(4),Gly(7)]-OT in a reversible manne r and blocked by the OT receptor antagonist desGly-NH29, d(CH2)(5)-[Tyr(Me) (2),Thr(4)]-ornithine-vasotocin. OT has no effect, however, on the membrane currents evoked by exogenous application of GABA. These results demonstrat e that OT depresses GABA(A) receptor-mediated sIPSCs in MTT cells by a pres ynaptic mechanism. (C) 2000 Elsevier Science ireland Ltd. All rights reserv ed.