Spinal cholinergic inhibition of the pressor response to muscle activation is mediated by muscarinic, but not nicotinic, receptors

This study examined the influence of spinal muscarinic and nicotinic receptors on the cardiovascular adjustments to skeletal muscle activation in anesthetized cats. Microdialyzing into the L(7) dorsal horn increasing doses of the muscarinic receptor agonist bethanechol, but not the nicotinic receptor antagonist mecamylamine, reduced increases in mean arterial pressure (MAP) and heart rate (HR) during hindlimb contraction or passive stretch. Atropine administration accentuated the cardiovascular responses during contraction, but not during passive stretch. These data indicate that muscarinic, but not nicotinic, receptors at the dorsal horn level blunt the pressor response to muscle activity. Further, the data suggest that the two neural pathways involved in muscle contraction or stretch are anatomically distinct.