Distribution and vasomotor effects of peptide HI (PHI) in feline cerebral blood vessels in vitro and in situ.
Peptide HI (PHI)-immunoreactive nerve fibres were numerous around cerebral blood vessels of the cat. The number and distribution resemble that previously found for vasoactive intestinal polypeptide (VIP), a peptide with which PHI co-exists in pial arteries, at least in some segments. PHI and VIP elicit dilatation in a concentration-dependent manner in isolated middle cerebral arteries; the maximum effects were similar but VIP was considerably more potent. Neither effect was blocked by atropine, cimetidine or propranolol, confirming an action at a non-adrenergic, non-cholinergic site. In chloralose-anaesthetized cats PHI and VIP elicited concentration-dependent dilatations; the magnitude of responses was similar, however, considerably more PHI was necessary to elicit the same response as that of VIP. The results suggest that though both peptides are co-localized and may act at the same receptor, VIP is a more likely candidate for eliciting dilatation during physiological conditions.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002415:Cats; D002536:Cerebral Arteries / Q000294:innervation / Q000502:physiology*; D002927:Cimetidine / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology; D015237:Dinoprost; D007120:Immunochemistry; D066298:In Vitro Techniques; D009412:Nerve Fibers / Q000378:metabolism*; D010451:Peptide PHI; D010455:Peptides / Q000378:metabolism / Q000494:pharmacology*; D010841:Pia Mater / Q000098:blood supply; D011433:Propranolol / Q000494:pharmacology; D011460:Prostaglandins F / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
D010451:Peptide PHI; D010455:Peptides; D011460:Prostaglandins F; D014660:Vasoactive Intestinal Peptide; D001285:Atropine; D002927:Cimetidine; D011433:Propranolol; D015237:Dinoprost; D003042:Cocaine