Participation of the parasympathetic and sympathetic nerves in regulation of gallbladder motility in the dog.

The participation of the parasympathetic and sympathetic nerves in the canine gallbladder motility was examined. Efferent stimulation of the parasympathetic (vagus) and sympathetic (celiac) nerves caused contraction or inhibition of the neck, body and fundus of the gallbladder. The contractile response induced by vagus nerve stimulation was reduced by subthreshold efferent stimulation of the celiac nerve, while the inhibitory response was neither reduced nor enhanced by subthreshold efferent stimulation of the celiac nerve. The contractile and inhibitory response induced by celiac nerve stimulation was not reduced in the neck, body and fundus by subthreshold efferent stimulation of the vagus nerve. The contractile response to vagus nerve stimulation was reversed to a relaxant response by atropine administration, which was reduced or abolished by hexamethonium. It is suggested that the vagus nerve-induced contractile response in the canine gallbladder is modulated by sympathetic nerves presynaptically at the vagus nerve endings in the enteric ganglion, but the vagus nerve-induced relaxant response, which probably was induced by non-adrenergic non-cholinergic inhibitory neurons, is not modulated by the sympathetic nerves.