Central imidazoline receptors as a target for centrally acting antihypertensive drugs.

Imidazoline (I1)-receptors in the central nervous system play a role in the central regulation of blood pressure and heart rate. Stimulation of these receptors in the rostral ventrolateral medulla induces peripheral sympathoinhibition, and hence a reduction of elevated blood pressure. The imidazoline derivatives moxonidine and rilmenidine are moderately selective I1 receptor stimulants which have been introduced as centrally acting antihypertensives. Since they have little affinity for alpha 2-adrenoceptors, they may be expected to cause less sedation and dry mouth than the alpha 2-adrenoceptor agonists clonidine and methyldopa. The concept of I1 receptors and their agonists therefore offers the possibility to develop centrally acting antihypertensives with a more favourable profile of adverse reactions than the classical alpha 2-adrenoceptor stimulants such as clonidine and methyldopa.