DIFFERENT EFFECT OF OXYTOCIN ON MEMBRANE-POTENTIAL OF SUPRAOPTIC OXYTOCIN NEURONS IN VIRGIN FEMALE AND MALE RATS IN-VITRO

The effects of oxytocin on membrane potential were investigated in the supraoptic nucleus (SON) neurons of rats using whole-cell patch-clamp technique. SON neurons were electrophysiologically identified as oxyt ocin (OT) or vasopressin (VP) neurons. Application of OT (1 x 10(-7) M ) hyperpolarized membrane potentials of OT neurons in virgin female ra ts but depolarized membrane potentials of putative OT neurons in male rats. The membrane conductance of SON neurons were increased by treatm ent of OT in both sexes, suggesting that OT increased the opening of c hannels on SON neurons. The reversal potential of OT neurons in virgin female rats and putative OT neurons in male rats under OT effective c onditions were -66 +/- 1 mV (n = 4) and -46 +/- 2 mV (n = 5), respecti vely. These data suggest that OT released within the SON suppresses th e activity of OT neurons in virgin female rats while it excites putati ve OT neurons in male rats. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.