Vagal stimulation and exogenous acetylcholine in isolated rat stomach: calcitonin effect on contractile activity

Calcitonin induces contraction in the vascular and extravascular smooth muscle and facilitates the transmission of the excitation in somatic motor nerve endings. These actions are Ca2(+)-dependent. The calcitonin effect on autonomic nerve endings has been studied here by testing influence of calcitonin on the contractile responses of the isolated rat stomach. The organ was submitted to electrical vagal stimulation or, after denervation, to exogenous acetylcholine. Calcitonin invariably increased the muscular tone and reduced the contractile responses to vagal stimulation. Opposite effects were noted after a serotoninergic block with nicergoline. Calcitonin also increased the contractile response evoked by exogenous acetylcholine and the Ca(2)-antagonist nicardipine counteracted the facilitatory effects. We suggest that the inhibitory action of calcitonin is serotonine-dependent while the facilitatory one is Ca2(+)-dependent.