1989 Volume 39 Issue 4 Pages 487-496
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 1.0μg and a volume of 2.0μl 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 1100h, and a decrease when injected at 1900h. Thus, a time-dependent fluctuation in the VIP effect on the hypothalamic neuronal activity was suggested.
