ENDOGENOUS AVP SYSTEMS REGULATE ORAL BEHAVIOR IN THE RAT FETUS - NEUROPEPTIDE SYSTEMS AS ONTOGENIC ADAPTATIONS

Pharmacological manipulation of V-1 receptors in rostral and caudal br ain regions alters perioral responsiveness in the E20 rat fetus. Block ade of caudal V-1 receptors or activation of rostral V-1 receptors red uces fetal responsiveness to perioral cutaneous stimulation. Activatio n of caudal V-1 receptors or blockade of rostral V-1 receptors increas es fetal responsiveness to perioral stimulation, including oral captur e and grasping of an artificial nipple. These results suggest that V-1 receptor-containing neurons regulate perioral responsiveness in the E 20 rat fetus and that the 2 populations of neurons exhibit functional differences. The caudal part of the arginines-vasopressin (AVP) system increases whereas the rostral part decreases responsiveness to differ ent types of perioral stimuli. The neuropeptide AVP may affect sucklin g behavior immediately after birth by regulating perioral sensory resp onsiveness.