Octopamine and phenylethylamine inhibit prolactin secretion both in vivo and in vitro

In the present work, we examined the action of two trace amines, octopamine and phenylethylamine, which are found in the hypothalamus, on pituitary hormone secretion in different experimental situations in vivo and in dispersed anterior pituitary cells. Both octopamine and phenylethylamine decreased high prolactin levels due to swimming or immobilization stress without affecting other adenohypophysial hormones. This is the first description of a specific endocrine action both in vivo and in vitro for octopamine and phenylethylamine. Further studies are needed to ascertain the physiologic or pathologic implication of these findings.