Clonidine on the pressor response to raised intracranial pressure

We attemptedto clarify the mechanism of the pressor response to raised intracranial pressure (ICP) in urethane-anesthetized rabbits. Intraventricular clonidine inhibited the pressor response to raised ICP, and intraventricular phentolamine antagonized the inhibitory effect of clonidine on the pressor response. In reserpine-treated rabbits the pressor response to raised ICP was not observed. Following intraventricular norepinephrine, however, the pressor response was observed. Intraventricular clonidine inhibited the pressor response that could be observed in the reserpine-treated rabbits following the intraventricular norepinephrine. These results suggest that the central sympathetic neurons play an important role in producing the pressor response to raised ICP.