Role of the autonomic nervous system in the rabbit sphincter of Oddi.

In vivo myoelectrical activity and pressure of the SO have been studied in intact, vagotomized and splanchnicectomized rabbits. Preganglionic nerve sections made no significant differences compared to the control group. Acetylcholine (3-11 mu g/kg) and adrenaline (1-50 micrograms/kg) increased and decreased respectively the myoelectrical activity. Hyoscine (0.5 mg/kg) and verapamil (35 micrograms/kg/min.) but not pentolinium (2 mg/kg) inhibited the excitatory activity of ACh; phentolamine (3 mg/kg) but not propranolol (3 mg/kg) antagonized the inhibitory activity of adrenaline. It can be concluded that the neurotransmission in the rabbit SO has both pathways: excitatory transmission mediated by cholinergic muscarinic receptors which are calcium dependent, and relaxation mediated by inhibitory alpha-adrenoceptors.