[Pharmacological analysis of the role of central alpha-2 adrenergic and imidazoline receptors in mechanism of the hypotensive effect of clonidine in rats].

The role of alpha 2-adrenergic and imidazoline receptors in the hemodynamic response to clonidine (manifested by reduced arterial pressure, heart rate, and renal blood flow rate) was studied by injecting their antagonists with different affinity (yohimbine and idazoxan) into narcotized Sprague--Dawley rats. The local introduction (microinjection into rostral ventrolateral medulla) and systemic administration (intraperitoneal injection) of the drugs showed that the hemodynamic effect of clonidine is mediated predominantly by the central alpha 2-adrenergic receptors, rather than by the imidazoline receptors.