Effects of propranolol on the cardiovascular responses to intracranial pressure elevation in rats

This study was performed to examine the effects of propranolol on the cardiovascular responses to intracranial pressure (ICP) elevation in rats. Intracranial pressure was raised by infusion of artificial cerebrospinal fluid into a lateral ventricle of rat's brain. Graded increases in ICP (from base line 7 mmHg 40 mmHg and then 60 mmHg) produced a graded reduction in regional cerebral blood flow (measured with a laser Doppler flowmeter at the parietal lobe). The ICP was claimed at each level for 5 min. ICP elevation also produced an increase in both mean arterial pressure and heart rate. Furthermore, 5 min after the termination of ICP elevation, a rebounding cerebral hyperemia was observed in control rats. It was found that pretreatment of animals with an i.p. doses of 2 mg/kg of propranolol significantly reduced both the tachycardia induced by ICP elevation and the cerebral post-ischemic hyperemia. However, the hypertension induced by ICP elevation was not affected by propranolol. The results suggested that beta-adrenergic mechanisms maybe involved in the cardiovascular responses to ICP elevation.