Pharmacological evidence in vitro and in vivo for functional beta1 receptors in the cerebral circulation

Abstract

Blood flow in the caudate nucleus was measured by the thermoclearance technique in non-anesthetized rabbits, accompanied by recording of electrocorticogram, systemic blood pressure, andPa _{O 2} andPa _{CO 2} (mass spectrometry). Isoprenaline increased caudate nucleus blood flow and reduced systemic blood pressure. The beta₂-receptor agonist, terbutaline, on the other hand, had only peripheral effects. The caudate nucleus flow response was selectively blocked by the beta₁-receptor antagonist, practolol, whereas propranolol inhibited all effects of both agonists. Isoprenaline dilated isolated pieces of the tributary artery (middle cerebral) tested in cats, the effect being inhibited not only by propranolol but also by practolol. The results offer further evidence for the view that the beta-receptors in the cerebral vascular bed are of the beta₁-type.