Biol Reprod Keystone Symposia Conference on Frontiers in Reproductive Biology & Regulation of Fertility.
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Biology of Reproduction 59, 670-675 (1998)
©Copyright 1998 Society for the Study of Reproduction, Inc.

Vasoactive Intestinal Peptide Secretion by Turkey Hypothalamic Explants1

Yupaporn Chaisehaa, Orlan M. Youngrenb, , and Mohamed E. El Halawani2,a

a Department of Animal Science b and Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota 55108

The objective of this study was to culture turkey hypothalami and examine vasoactive intestinal peptide (VIP) release during the turkey reproductive cycle. The release of VIP was studied employing a computer-guided perifusion system. Hypothalami were perifused with Krebs-Ringer bicarbonate medium for 10 or 15 h at a flow rate of 40 µl/min, and perifusate was collected at 5-min intervals. Basal VIP secretion increased (p < 0.05) over time, and no differences in release rate were noted between reproductive stages. Basal VIP release during perifusion was episodic throughout each experimental period. Perifusion with dopamine (DA; 10 and 100 nmol/min) in incubating hens stimulated VIP release in a dose-dependent manner. There were no significant differences (p > 0.05) in VIP release in response to DA stimulation between hypothalamic fragments obtained from nonphotostimulated and incubating birds. The data suggest that 1) a VIP pulse generator appears to be located within the turkey hypothalamus, on the basis of the observed pulsatile release of VIP; 2) hypothalamic secretion of VIP is augmented by removal of inhibitory factors residing outside of the hypothalamus, or by the loss of negative feedback mechanisms that inhibit VIP release; and 3) mechanisms responsible for altering VIP release during different reproductive conditions may lie external to the hypothalamus.

1 This is Scientific Journal Series Paper 22,534 of the Minnesota Agriculture Experiment Station. Research supported by USDA Grant No. 97-35203-4960.

2 Correspondence: Mohamed El Halawani, 495 Animal Science/Veterinary Medicine, 1988 Fitch Avenue, University of Minnesota, St. Paul, MN 55108. FAX: (612) 625-2743; elhal001{at}maroon.tc.umn.edu






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Copyright © 1998 by the Society for the Study of Reproduction.