PMID: 8968369Dec 1, 1996Paper

Partial agonism of the nonselective adenosine receptor agonist 8-butylaminoadenosine at the A1 receptor in vivo

The Journal of Pharmacology and Experimental Therapeutics
R A MathôtM Danhof

Abstract

The cardiovascular effects of the nonselective adenosine receptor agonist 8-butylaminoadenosine (BAA) were quantified in conscious normotensive rats. The potency and intrinsic activity for the A1 and A2a receptor were determined separately. The rats received a short intravenous infusion of 100 mg/kg BAA in combination with a continuous infusion of either the A1-selective antagonist 8-cyclopentyltheophylline (CPT) (8 micrograms/min/kg), the A2a-selective antagonist 8-(3-chlorostyryl)caffeine (CSC) (32 micrograms/min/kg) or the vehicle. Heart rate (HR) and mean arterial pressure (MAP) were recorded continuously as pharmacodynamic indices for adenosine receptor activation. The MAP/HR ratio was derived as an additional cardiovascular parameter. This ratio reflects changes in total peripheral resistance on the assumption that stroke volume remains constant. During the infusion of CSC, the potency and intrinsic activity for the A1 receptor were estimated by relating the negative chronotropic effect to BAA blood concentrations. The sigmoidal curve yielded a potency value based on unbound concentrations (EC50,u) of 1.9 +/- 0.4 micrograms/ml (mean +/- S.E.; n = 5). The maximal reduction (Emax) in HR (-85 +/- 9 beats/min) was significant...Continue Reading

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