Time-dependent effects of intrahypothalamic injection of vasoactive intestinal peptide on spontaneous motor activity in rats.

Abstract

In male Wistar rats, microinjection cannulae were stereotaxically implanted in the ventromedial and paraventricular hypothalamic nuclei. After control recordings of spontaneous motor activity for 4-6 days, vasoactive intestinal peptide (VIP) was injected in a dose of 1.0 pg and a volume of 2.0 pl into these nuclei at 1100 or 1900h, and the activity during the 3-h period following was compared with that on the control days in individual animals. VIP injection produced an increase when injected at 1100 h, and a decrease when injected at 1900 h. Thus, a timedependent fluctuation in the VIP effect on the hypothalamic neuronal activity was suggested.

Changes in Vasoactive Intestinal Peptide Binding Site Densities in the Female Rat Central Nervous System and Pituitary During Lactation

“…The hypothalamic ventromedial nucleus and PVN have been identified as important sites mediating feeding and drinking behavior (40)(41)(42)(43). Intrahypothalamic injection of VIP into these areas has been assumed to influence neuronal activity based on the potent effects this peptide has on motor behavior (44). VIP receptor density was increased in the PVNAp during lactation and was decreased by pup removal.…”