Effects of azepexole and clonidine on baroreceptor mediated reflex bradycardia and physiological tremor in man.

Abstract

1 The effects of oral administration of axepexole 10 mg, clonidine 300 ,ug and placebo on baroreceptor mediated reflex bradycardia and physiological tremor were investigated in six healthy volunteers. 2 Both azepexole and clonidine reduced (P < 0.05) systolic (120.5 ± 2.5 to 105.0 + 3.3 mm Hg; 115.8 + 2.6 to 104.7 + 2.8 mm Hg respectively) and diastolic (52.5 + 2.6 to 47.2 + 1.4 mmHg; 53.7 + 1.6 to 49.0 ± 1.5 mmHg respectively) pressure when compared to placebo and to pre-treatment values. This reduction in pressure was not accompanied by a change in heart rate. 3 Both azepexole and clonidine enhanced (P < 0.05) baroreflex sensitivity to increases in systolic arterial pressure with phenylephrine. 4 Clonidine facilitated (P < 0.05) baroreflex sensitivity during the strain phase of the Valsalva manoeuvre, whereas azepexole reduced it (P < 0.05). 5 Neither clonidine nor azepexole altered finger tremor when compared to placebo or pre-treatment values. 6 Azepexole produced (P < 0.05) sedation compared to placebo but not when compared to pre-treatment values. Clonidine caused significant increases in sedation when compared to both placebo and to pre-treatment values. 7 The differences between azepexole and clonidine may be due to the greater specificity of azepexole for the a2-adrenoceptor than clonidine.

Comparison of the effects of high ambient temperature and clonidine on autonomic functions in man

“…This observation is in agreement with our earlier report about the lack of effect of a single oral dose (200 lg) of clonidine on the enhancement of finger tremor evoked by high ambient temperature (Fleming et al 1991). This observation is in agreement with the report of Harron et al (1985) of the lack of effect of clonidine on baseline tremor and also with our earlier observation of the lack of effect of a single oral dose (200 lg) of clonidine on the enhancement of finger tremor evoked by high ambient temperature (Fleming et al 1991). It should be noted, however, that the lack of effect of clonidine on both baseline and temperature-enhanced finger tremor may have reflected the relative lack of sensitivity of the finger tremor test to detect drug-induced changes.…”

Hemodynamic effects of dexmedetomidine in isoflurane-anesthetized cats

“…Alpha‐2 agonists have been shown to cause decreases in heart rate by increasing baroreceptor responses to increases in blood pressure, decreasing sympathetic tone, and/or increasing parasympathetic tone (Badoer et al. 1983; Harron et al. 1985; Devcic et al.…”

Increased central alpha2-adrenoceptor sensitivity in panic disorder

“…Normally hypotension is accompanied by a compensatory tachycardia via baroreceptor stimulation. Clonidine, as well as producing a bradycardia by directly increasing vagal outflow, also prevents this reflex by resetting baroreflex sensitivity (Harron et al 1985). It is possible that in panic disorder baroreceptor control is more sensitive to clonidine.…”