D-Fenfluramine activates rat oxytocinergic and vasopressinergic neurons through different mechanisms

Activation of serotonin neurotransmission produces increase of plasma oxyto cin, prolactin, vasopressin and ACTH levels. Using dual-immunocytochemistry , the number of oxytocinergic neurons in the hypothalamic magnocellular nuc lei co-storing Fos after administration of D-fenfluramine was found to be 1 5-fold higher compared to vehicle, comprising about 30% of the total number of these neurons. Vasopressinergic neurons were virtually not affected. Th ese results show that serotonergic neurotransmission induces Fos transcript ion in oxytocinergic neurons that may lead to a release of oxytocin to the general circulation, whereas vasopressinergic neurons are activated through another mechanism. (C) 1999 Elsevier Science B.V. All rights reserved.