| Research Abstract |
Effects of adenosine receptor agonists of the pancreatic exocrine secretion were examined in anesthetized dogs. Graded doses of CGS21680 (1-300 nmol/kg), a selective adenosine A_<2A> receptor agonist, produced dose-dependent increasein the secretory rate of pancreatic juice, with a maximum effect at approximately 30 nmol/kg. However, CPA (1-300 nmol/kg), a selective adenosine A_1 receptor agonist, did not cause the pancreatic secretion. CGS21680 (3-30 nmol/kg) and secretin (0.01-0.03 pmol/kg) increased the bicarbonate concentration in pancreatic juice and decreased the protein concentration. DMPX (5-50 nmol/kg), a weak adenosine A_<2A> receptor antagonist, caused a progressive parallel shift to the right in the dose -response curve for CGS21680-induced pancreatic secretion without changes in the maximal response. DPCPX (100 nmol/kg), a selective A_1 adenosine receptor antagonist, did not antagonize the CGS21680-induced pancreatic secretion. These results suggest the existence of adenosine A_<2A> receptors in the exocrine cells of dog pancreas, involved in the water and bicarbonate secretory response.
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