Cardiovascular pharmacology of the A2A adenosine receptor antagonist, SCH 58261, in the rat.
We characterized the in vivo cardiovascular profile of SCH 58261, 7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2, 4-triazolo[1,5-c] pyrimidine, a selective A2A adenosine receptor antagonist, in conscious, freely moving rats by use of the telemetry system. In normotensive rats, SCH 58261, at 10 mg/kg i.p., significantly (P < .05) inhibited hypotension and tachycardia induced by the A2A receptor agonist 2-hexynyl-5'-N-ethylcarboxamidoadenosine (0.01 mg/kg i.p.), but not the bradycardic effect caused by the A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (0.03 mg/kg i.p.). SCH 58261, when administered alone, at 0.1 and 1 mg/kg i.p., did not induce significant hemodynamic changes, but at 10 mg/kg i.p., it slightly increased both systolic blood pressure (SBP) and diastolic blood pressure (DBP) (+19 +/- 3 and +16 +/- 2 mm Hg, respectively; P < . 01) and heart rate (HR) (+85 +/- 5 beats/min; P < .01). These effects were inhibited by adrenergic blockade with propranolol (30 mg/kg i.p.) and phentolamine (10 mg/kg i.p.): -5 +/- 3 mm Hg on DBP and -12 +/- 11 beats/min on HR (P < .01). In spontaneously hypertensive rats, SCH 58261, at 3 and 10 mg/kg i.p., increased weakly both SBP (+19 +/- 5 mm Hg and +25 +/- 4 mm Hg) and DBP (+14 +/- 4 mm Hg and +23 +/- 4 mm Hg) vs. vehicle (P < .01) and HR (+45 +/- 17 and +64 +/- 18 beats/min vs. vehicle, respectively; P < .01). The data indicate that SCH 58261 retains A2A selective receptor antagonist properties in vivo. Its effect on cardiovascular sympathetic outflow further suggests that endogenous adenosine exerts a tonic vascular regulation through A2A receptors. Therefore, SCH 58261 can be a useful pharmacological tool for clarifying A2A-mediated cardiovascular actions of adenosine.
Monopoli
A
A
Schering-Plough Research Institute, San Raffaele Science Park, I-20132, Milan, Italy.
Casati
C
C
Lozza
G
G
Forlani
A
A
Ongini
E
E
D018674:Adrenergic Antagonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004347:Drug Interactions; D006339:Heart Rate / Q000187:drug effects*; D006439:Hemodynamics / Q000187:drug effects; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D058915:Purinergic P1 Receptor Antagonists; D011743:Pyrimidines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014230:Triazoles / Q000494:pharmacology*
C098657:5-amino-7-(2-phenylethyl)-2-(2-furyl)pyrazolo(4,3-e)-1,2,4-triazolo(1,5-c)pyrimidine; D018674:Adrenergic Antagonists; D058915:Purinergic P1 Receptor Antagonists; D011743:Pyrimidines; D014230:Triazoles; D011433:Propranolol; D010646:Phentolamine