Pharmacological study of cholinergic system on cardiovascular regulation in the cuneiform nucleus of rat

• Microinjection of Ach in CnF induced hypotension with no effect on HR.
• Blockade of muscarinic receptors by atropine in CnF strongly attenuate hypotension induced by Ach.
• Blockade of nicotinic receptors by hexametunium in CnF slightly attenuate hypotension induced by Ach.
• Effect of CnF muscarinic receptor in cardiovascular regulation is higher than nicotinic receptor.

In the present study the effect of cholinergic system of Cuneiform nucleus (CnF) on central regulation of cardiovascular system was investigated. Two doses of acetylcholine (Ach; 90 and 150 nmol), atropine (3 and 9 nmol) and hexamethonium (Hexa; 100 and 300 nmol) were microinjected into the CnF. The maximum changes of MAP and HR were compared with control group (independent t-test). Both doses of Ach significantly decreased MAP but had no significant effect on HR. Administration of atropine and Hexa by themselves did not alter the MAP or HR. However, both doses of atropine and higher dose of Hexa significantly attenuated the hypotensive effect of Ach with no significant effect on HR. Our results suggest the involvement of CnF cholinergic system only on central blood pressure regulation that strongly mediated by muscarinic receptors.