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  • Title: Vasoactive intestinal peptide secretion by turkey hypothalamic explants.
    Author: Chaiseha Y, Youngren OM, El Halawani ME.
    Journal: Biol Reprod; 1998 Sep; 59(3):670-5. PubMed ID: 9716568.
    Abstract:
    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 microliter/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.
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