Abstract
Summary
On the morning of proestrus or estrus, mature rats were injected with an extract of eight rat hypothalami or an equivalent amount of cerebral tissue. Blood was removed just prior to injection of hypothalamic extract and at 1 and/or 4 hr after injection, for assay of prolactin by radioimmunoassay. In each of the three experiments, hypothalamic extract significantly depressed serum prolactin values, confirming the presence of prolactin-inhibiting activity in the hypothalamus. Cerebral extract had no effect. In another experiment, the litters of postpartum lactating rats were removed for 12 hr and the rats were injected with an extract of four or eight rat hypothalami or an equivalent amount of cerebral tissue. The litters were then returned for 3 hr of suckling. Blood samples taken before and after suckling, showed that neither brain extract prevented the suckling stimulus from producing a 5- to 6-fold increase in serum prolactin values. This indicates that 3 hr of suckling is a more powerful stimulus to prolactin release than a single injection of hypothalamic extract on inhibition of prolactin release.
Get full access to this article
View all access options for this article.