Mechanism of the hypotensive action of practolol in the anesthetized rat

Cardiovascular effects of acute administration of practolol were studied in groups of normotensive and spontaneously hypertensive rats. In some of these animals a strong and long-lasting hypotension was shown, resulting from a decrease in the total peripheral resistance. This hypotension was impaired by preventive propranolol administration, and did not result from a direct vascular effect. Moreover, it was previously reported that practolol induced a strong and long-lasting hypotension in all normotensive and hypertensive rats after blood-brain barrier disruption. From these experiments it is suggested that the blood pressure decrease observed in some groups of Okamoto rats may be due to a practolol action on central beta-receptors. The intensity of hypotension depends on the molecule penetration in the central nervous system, and seems to be related to blood-brain barrier lesions induced by genetic hypertension.