The Relationship Between Increased Intracranial Pressure and Central alpha-Adrenoceptors

ABSTRACT

The author attempted to clarify the nature of alpha-adrenoceptors in relation to the pressor response to the increased intracranial pressure(ICP) in urethane-anesthetized rabbits, using the epidural balloon method. 1) The blood pressure increased in parallel with the raised ICP which was made by gradual inflation of the balloon. 2) B-HT 920, an alpha2-agonist, which elicited depressor and bradycardiac responses in normal rabbits inhibited markedly the pressor response to the raised ICP. 3) Piperoxan, an alpha2-antagonist, potentiated the pressor response to the raised ICP. 4) Piperoxan antagonized the depressor and bradycardiac responses by B-HT 920 as well as the inhibitory effect of B-HT 920 on the pressor response to the raised ICP. 5) The pressor response to the raised ICP were not affected at all by prazosin, an alpha1-antagonist. 6) Neither the depressor and bradycardiac responses by B-HT 920 itself nor the inhibitory effect of B-HT 920 on the pressor response to the raised ICP were significantly affected by prazosin. It is inferred from these observations that the central alpha-adrenoceptors play an important role in producing the pressor response to the raised ICP and that the receptors involved here seems to be of alpha2-type.