Distribution and vasomotor effects of peptide HI (PHI) in feline cerebral blood vessels in vitro and in situ |
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Authors: | Lars Edvinsson James McCulloch |
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Institution: | a Department of Clinical Pharmacology, University Hospital of Lund, Lund, Sweden b The Wellcome Surgical Institute, University of Glasgow, Glasgow, U.K. |
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Abstract: | 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. |
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Keywords: | cerebrovascular nerves vasoactive intestinal polypeptide (VIP) peptide HI (PHI) vasomotor effects dilatation |
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