The effects of oxytocin and vasotocin analogues on the responses of rat brainstem neurones to oxytocin.

The effects of microiontophoretically applied oxytocin on the firing rates of neurones in the rat caudal brainstem have been examined. Of the sample of 156 units recorded the firing rates of 33.3% were reduced and those of 21.2% were raised by microiontophoretically applied oxytocin, whilst the remainder were unaffected. The distribution of units facilitated by oxytocin tended to overlap with the distribution of oxytocin demonstrated immunocytochemically, whereas many units inhibited by oxytocin were in regions where no oxytocin was observed. Overall the excitatory but not the inhibitory effects of oxytocin could be blocked by oxytocin and vasotocin analogues with antagonist properties.