2018 Volume 89 Issue 1 Pages 13-17
Most oxytocin cells distributing separate nuclei in the hypothalamus display synchronous high frequency burst discharge preceding each milk ejection in lactating rats. We have suggested that excitatory neural connections between oxytocin cells distributing separate nuclei are involved in the synchronization of bursting discharge of oxytocin cells. In the present experiment, to examine whether oxytocinergic synapse intervening excitatory neural connections between oxytocin cells are involved in the occurrence of synchronized bursting discharge of oxytocin cells preceding milk ejection, effects of intraventricular administration of atosiban which has antagonizing effect of oxytocin or vasopressin receptor was were tested in lactating suckled mother rats. Intraventricular administration of atosiban decreased the frequency of milk ejection. Amount of oxytocin released at each milk ejection was decreased following intraventricular administration of atosiban. The results of the present experiments indicate that central oxytocin is involved in the occurrence of milk ejection. It was suggested that excitatory neural connections between oxytocin cells distributing separate nuclei are involved in the timing of milk ejection and amount of oxytocin released at each milk ejection, because intraventricular administration of atosiban affected the frequency of milk ejection and the amplitude of increase of intramammary pressure at each milk ejection.
