An introduction to the pharmacology of alpha 2-adrenoceptors in the central nervous system.

alpha 2-Adrenoceptors mediate a variety of physiological functions in the central nervous system and in peripheral tissues; thus, the use of pharmacological agents either activating or blocking these receptors results in a mixture of responses from several organs and tissues. This may be utilized therapeutically in some situations. In anaesthesiology, alpha 2-adrenergic agonists are already widely used as veterinary sedative-analgesics, and it is now clear that they are also capable of potentiating the effects and reducing the required dosage of other drugs used in anaesthesia (barbiturates, volatile anaesthetics, narcotic analgesics). In addition, they attenuate sympatho-adrenal responses to noxious stimuli encountered during anaesthesia and surgery, providing improved hemodynamic, metabolic and hormonal stability. Recent results from molecular biology, biochemistry and pharmacology point to the existence of distinct alpha 2-adrenoceptor subtypes. The identification of such subpopulations of alpha 2-adrenoceptors may provide new opportunities for the development of subtype-selective pharmacological agents with more specific therapeutic actions.