In the isolated internal anal sphincter of the guinea-pig, adenosine 5'-triphosphate (ATP) and adenosine induced a concentration-dependent and tetrodotoxin-insensitive relaxation. Pretreatment with theophylline (25-50 μM) had no significant effect on the concentration-response curves obtained with either purine compound. Reactive blue 2 (25-100 μM) shifted the curve to ATP to the right in a dose-dependent fashion leaving that to adenosine unaltered. The antagonism appeared to be non-competitive. Neither reactive blue 2 nor purine receptor occupation by ATP or adenosine altered the electrically-induced non-adrenergic, non-cholinergic inhibitory response. The actions of ATP and adenosine in the guinea-pig internal anal sphincter appear to be mediated by separate receptors. These receptors are not involved in the nerve-mediated relaxation.
|Number of pages||5|
|Journal||British Journal of Pharmacology|
|Publication status||Published - 1983|
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