ABSTRACT
Moxonidine is a new second generation, centrally acting antihypertensive drug. It causes peripheral sympathoinhibition, triggered at the level of central nervous 11-receptors. The present study was designed to screen various cardiovascular effects of moxonidine both in-vivo and in-vitro as well as to investigate the possible analgesic effect of moxonidine. In-vitro results revealed that moxonidine produced dose related inhibition of the force of contraction of the isolated perfused rabbit's heart. A vagal like action was suggested because both muscarinic and nicotinic receptors antagonist abolished this effect. In vivo results showed that acute intravenous injection of moxonidine significantly reduced heart rate of normotensive rats dose dependantly. Moxonidine in different doses exhibited pronounced antiarrhythmic effects characterized by dose-dependent increase in adrenaline arrhythmogenic dose and significant decrease in the number of extrasystoles. Furthermore, moxonidine in different doses, increased both the arrhythmogenic and ventricular fibrillatory doses of ouabain in a dose-dependent manner. Lastly, acute moxonidine administration was found to provide potent antinociceptive efficacy in control of acute pain in rats and yohimbine, was able to antagonize this effect