Effect of Clonidine and Regitine on the Pressor Response to Raised Intracranial Pressure in Rabbits

ABSTRACT

1. It was attempted to clarify the mechanism of the pressor response to raised intracranial pressure in urethane-anesthetized rabbits. 2. Intraventricular clonidine markedly inhibited the pressor response to raised intracranial pressure. 3. Intraventricular regitine antagonized the above mentioned inhibitory effect of clonidine on the pressor response. 4. In reserpine-treated rabbits the pressor response to raised intracranial pressure was not observed, whereas after the intraventricular administration of norepinephrine the pressor response was observed. 5. Intraventricular clonidine inhibited the pressor response that could be observed in the reserpine-treated rabbits after the intraventricular norepinephrine. 6. It is inferred that raised intracranial pressure stimulated some part of the brain to cause the increase of norepinephrine release, resulting in the increase of the sympathetic outflow and the elevation of blood pressure.