Participation of cholinergic pathways in sinoaortic denervated rats

Seven days after sinoaortic denervation (SAD), mean blood pressure (MBP) and heart rate measured in conscious rats were not significantly different from sham-operated animals. A high dose of atropine, 8 mg kg-1, reduced MBP only in SAD rats. Atropine, 0.08-0.8 mg kg-1, or methylatropine, 0.8 mg kg-1, induced tachycardia in sham rats. This effect was reduced after sinoaortic denervation and it involves peripheral muscarinic receptors. The hypertension and tachycardia provoked by physostigmine were more marked in SAD than in sham rats. The cardiovascular responses induced by physostigmine were abolished by atropine and were not affected by methylatropine. The hypertension caused by physostigmine in SAD animals was more sensitive to the antagonism of atropine than in sham rats. Our results show that baroreceptor deafferentation affects peripheral parasympathetic tone to the heart and changes the cholinergic pathways involved in the modulation of cardiovascular response.