Drugs interacting with alpha adrenoceptors.

Alpha adrenoceptors should be divided into various subtypes, comprising pre/postsynaptic and alpha 1/alpha 2-subpopulations, respectively. This classification implicates important functional differences between the various alpha-receptor subtypes, including certain differences in signal transduction following receptor stimulation. After a brief synopsis of the modern classification of alpha-adrenoceptors and its functional implications, the emphasis of the present survey is laid upon the various drugs that interact with the different alpha-adrenoceptor subtypes. Accordingly, agonists and antagonists towards alpha 1- and alpha 2-adrenoceptors are discussed with respect to the pharmacologic basis of their therapeutic activity. Some attention is paid to alpha 1-adrenoceptor antagonists with additional pharmacological activities, e.g., labetalol, ketanserin, and urapidil. Finally, the indirect and rather subtle interaction of calcium antagonists and ACE inhibitors with alpha-adrenoceptor-triggered vasoconstriction is also dealt with, in particular with respect to the influence of these drugs on receptor-operated calcium channels and signal transduction following receptor stimulation.