The actions of atropine, tropenziline and N-butyl hyoscine bromide on the isolated distal colon of the guinea-pig: a comparison of their activities and mechanisms of action

In the guinea-pig isolated distal colon, the order of anticholinergic activity is as follows: atropine > tropenziline bromide > N-butyl hyoscine bromide. The reduction in the responses to pelvic and transmural stimulation produced by tropenziline and N-butyl hyoscine bromide is due partly to their ganglion blocking activity. This effect also explains the reduction they cause in acetylcholine output on pelvic nerve and transmural stimulation. Since atropine also reduces acetylcholine release on pelvic nerve stimulation, it is suggested that muscarinic receptors of the parasympathetic ganglia are involved in transmission of pelvic nerve impulses.