In order to define the
purinergic receptors subtype involved in the control of cardiovascular activity, the effects of intracerebroventricular (icv 3rd ventricle) or intravenous (i.v.) injection of
purinergic agonists and antagonists were evaluated on arterial blood pressure and heart rate of anaesthetized normotensive adult male rats.
Adenosine (
Ado) an A1 and A2
purinergic receptors agonist,
N6-cyclohexyladenosine (CHA), an A1 receptor agonist and 5'-(N-cyclopropyl)-carboxamidoadenosine (
CPCA), an A2
purinergic receptor agonist, were administered in rats by icv (0.01-0.05-0.1 microgram) and i.v. (0.1-0.5-1 microgram/kg)
injections. The animals treated with
adenosine were either pretreated with an A1 (8-cyclopenthyl-1,3-dimethylxanthine, CPT) an A2 (3,7dimethyl-1-propargylxanthine, DMPX) or an A1-A2 (
aminophylline, APH)
purinergic receptor antagonist by icv (0.05 microgram) or i.v. (0.5 microgram/kg) injected or not at all pretreated.
Ado,
CPCA and CHA produced a dose-dependent decrease in arterial blood pressure and heart rate. The effects of CHA were less marked than those caused by
Ado and
CPCA. The icv and i.v. pretreatment with
aminophylline,
CPT and
DMPX inhibited arterial
hypotension and
bradycardia induced by
Ado, CHA and
CPCA. The inhibitor effects of
aminophylline and
DMPX were stronger than those caused by
CPT. These results showed that in the cerebral areas near the 3rd ventricle the purinergic system plays an important role in the control of cardiovascular function. The involvement of A2
purinergic receptors after administration of
adenosine or its analogs on central and peripheral cardiovascular activity was also confirmed.