Effects of diazepam on the carotid sinus baroreflex control of circulation in rabbits

Abstract

To examine the effects of diazepam on the carotid sinus baroreflex control of circulation, bilateral carotid occlusion was performed on 14 conscious rabbits with aortic denervation. The responses of mean arterial pressure, heart rate, cardiac output and total peripheral resistance were obtained. The haemodynamic responses to carotid occlusion were evaluated at cumulative doses of 0.5 and 1.0 mg kg-1 of diazepam. The administration of diazepam decreased cardiac output and increased total peripheral resistance significantly, but did not affect the arterial pressure and heart rate. The response of total peripheral resistance to carotid occlusion was significantly increased from 0.118 +/- 0.018 (mean +/- SE) to 0.154 +/- 0.026 mmHg min ml-1 at 1.0 mg kg-1 of diazepam. The heart rate response was attenuated significantly from 41 +/- 5 to 24 +/- 4 beats min-1 at 1.0 mg kg-1 of diazepam. Diazepam did not alter the response of arterial pressure to carotid occlusion. We suggest that the dissociated effects of diazepam on the reflex control of circulation reflect the dissociated influences of diazepam on the central sympathetic and vagal-mediated pathways.

Electrocardiographic Changes during Exposure to Residual Oil Fly Ash (ROFA) Particles in a Rat Model of Myocardial Infarction

“…However, studies indicate that diazepam reduces vagal tone and suppresses vagally mediated reflexes in humans and large animals (Adinoff et al, 1992;Hockman and Livingston, 1971;Keim and Sigg, 1973;Marty et al, 1986;Sakamoto et al, 1990;Sigg et al, 1971;Taneyama et al, 1993). It is unlikely that the dose used in our experiments significantly reduced vagal tone, as our average baseline heart rates in both the sham-operated and MI animals were similar to those reported in the literature for conscious rats (e.g., Krüger et al, 2000;Opitz et al, 1995).…”