Cardiovascular responses to carotid and vertebral artery infusions of propranolol

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Abstract
The cardiovascular effects of intracarotid and intravertebral injections of propranolol were studied in open-chest anaesthetized dogs. After injection of 0.1 mg/kg propranolol into the common or internal carotid artery, a decrease in blood pressure started after a latent period of 2–3 sec. There was a slight but not significant decrease in heart rate, but no change in aortic flow or myocardial contractile force. Injection of propranolol into the vertebral artery induced a decrease in blood pressure after a latent period of 3–4 sec. By contrast, injection of the drug into the femoral artery caused a decrease in blood pressure only after a latent period of 7–8 sec. The injection of propranolol proximal or distal to the carotid bifurcation – that is, proximal or distal to the carotid chemo- and baro-receptors – did not change the magnitude or latent period of the pressure drop. We conclude that propranolol acts on some structure or structures in the central nervous system within the area of distribution of the carotid and/or vertebral arteries, and that this effect contributes to its hypotensive action. The carotid chemo- and baro-receptors apparently play no part in the decrease in blood pressure induced by the drug.

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