Bradycardic responses to vagal stimulation and methacholine injection in sinoaotic denervated rats

ABSTRACT

The bradycardia that occurs in response to vagal stimulation or to methacholine after 6 h of sinoaort denervation (SAD) was studied in SAD rats before and agter adrenergic blockade to determinewhether the peripheral vagal action was impaired by sympathetic hyperactivity. A marked attenuation in the response to methacholine and no difference in the responses to vagal stimulation were observed in SAD rats compared to sham-operated controls. The adrenergic blockade attenuated the responses to both vagal stimulation and nethacholine in control rats but not in SAD rats. These finding revealed an impairment of peripheral vagal function after 6 h of SAD, probaly due to a decreased sensitivity of the muscarinic receptors