Cholinergic influences on the spinal cardiovascular neurones.
1 In bilaterally vagotomized and spinal cord (C1) transected dogs, intrathecal (i.t.) injection of pilocarpine decreased while DMPP increased the blood pressure. These responses were antagonized by i.t. pretreatment with ethylbenztropine and chlorisondamine respectively. 2 No change in the resting heart rate occurred after intrathecal injection of cholinergic drugs in these animals. 3 The post-coronary artery ligation cardiac arrhythmia, in bilaterally vagotomized and spinal (C1) transected dogs, was inhibited by i.t. pilocarpine and chlorisondamine and facilitated by ethylbenztropine and DMPP. 4 The effects of muscarinic and nicotinic receptor agonists on the arrhythmia were blocked by their respective blockers. 5 It appears that the muscarinic receptors are inhibitory while nicotinic receptors are facilitatory for spinal control of vasomotor tone and the post-coronary artery ligation cardiac arrhythmia. However, the spinal muscarinic and nicotinic receptors do not appear to have a significant role in the regulation of normal heart rate.