Evidence that vasoactive intestinal polypeptide is a physiological prolactin-releasing factor in the XXXX hen.

@entity17548 @entity1420 @entity2931 @entity38615 @entity1573
Vasoactive intestinal polypeptide ( @entity38615 )-like material was localised immunohistochemically in the hypothalamus of the @entity1573 hen. Abundant immunoreactive @entity38615 terminals were seen in the external layer of the median eminence and most immunoreactive @entity38615 cell bodies were located in the basal hypothalamus. A few immunoreactive @entity38615 cell bodies and many fibres were found in the preoptic hypothalamus. Intravenous injections of synthetic porcine @entity38615 over a dose range of 12.5 to 100 micrograms kg-1 body wt resulted in dose-related increase in concentration of plasma prolactin in incubating @entity1573 deprived of their nests for 24 hr. These doses of @entity38615 did not stimulate the release of @entity17548 . Studies in vitro showed that synthetic @entity38615 directly stimulated prolactin release from the anterior pituitary gland. The glands from incubating @entity1573 were more responsive to the prolactin-releasing effects of @entity38615 than were the glands from laying birds. Studies in vitro showed that the amount of prolactin released in response to an iv injection of 50 micrograms kg-1 @entity38615 was greater in incubating birds deprived of their nests for 24 hr than in laying hens. Prolactin release was not stimulated in ovariectomized hens after an injection of 50 micrograms kg-1 @entity38615 unless the birds were first treated with @entity2931 or @entity2931 and @entity1420 . It was concluded that a @entity38615 -like material in the @entity1573 hypothalamus may be a physiological prolactin-releasing factor acting at least in part at the level of the anterior pituitary gland.(ABSTRACT TRUNCATED AT 250 WORDS)
