Vaginal distension induces milk ejection-related burst of oxytocin neurones interacting with suckling stimuli in lactating rats.

Milk ejection-related bursts of action potentials recurred at fairly regular intervals during suckling in oxytocin cells of anesthetized lactating rats. Additional milk ejection-related bursts were frequently induced in response to vaginal distension. The latency for the induced response was 2.9 +/- 0.2 s and the size of the induced bursts was similar to that of spontaneous ones. When animals were not suckled, the burst was in no case induced by the stimulus. The findings indicate that the two afferent stimuli arising from the mammary gland and vagina can interact with each other in generating milk ejection-related bursts of oxytocin cells.