Response of the parotid gland of red kangaroos, Macropus rufus, to phenylephrine stimulation.
Intracarotid infusions of l-phenylephrine at 1.0 or 10 nmol kg(-1) min(-1) were accompanied by increases in salivary amylase activity, protein, potassium, magnesium and chloride relative to cholinergically-stimulated saliva. Intravenous infusions of phenylephrine at the same dose rates had a lesser effect on salivary composition particularly protein. Propranolol administered with phenylephrine via the carotid artery, at an antagonist/agonist ratio of 10:1, was much more effective in blocking the phenylephrine-induced changes in salivary composition than equimolar infusion of phentolamine with phenylephrine. It was concluded that alpha(1)-adrenoreceptors were not present in functionally significant numbers in the gland and that the effect of phenylephrine on the kangaroo parotid was mediated by beta-adrenoreceptors. As the phenylephrine dose rates in the kangaroos were comparable with those used to determine alpha-adrenergic responses of eutherian salivary glands and as phentolamine appeared to have minor beta-sympathomimetic activity, at least one subtype of beta-adrenoreceptors in macropods may not be identical to its eutherian counterpart.
Beal
A M
AM
Faculty of Science, University of New South Wales, Sydney 2052, Australia. m.beal@unsw.edu.au
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000681:Amylases / Q000378:metabolism; D000818:Animals; D005260:Female; D007614:Macropodidae / Q000502:physiology*; D008297:Male; D010306:Parotid Gland / Q000187:drug effects* / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000378:metabolism; D012463:Saliva / Q000201:enzymology
D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D011941:Receptors, Adrenergic; D010656:Phenylephrine; D011433:Propranolol; D000681:Amylases