Effects of gastrointestinal hormones on the electrical and mechanical activity of the cat stomach.

Effects of gastrointestinal hormones on electrical and mechanical activity of smooth muscle of cat stomach were studied. Spontaneous electrical activity of the antrum preparation consisted of slow waves with superimposed spike-like potentials. Phasic contractions occurred synchronously with the electrical activity. Pentagastrin, tetragastrin, pancreozymin and secretin increased frequency of slow wave component and amplitude of phasic contraction. Atropine and tetrodotoxin did not block the spike-like potential and slow wave component. Noradrenaline and verapamil blocked the phasic contraction. The excitatory effects of these gastrointestinal hormones were observed in the presence of atropine, tetrodotoxin and dibenamine, but not in verapamil. When the mechanical activity of the antral strips was depressed by caffeine or theophylline, the excitatory effects of gastrointestinal hormones were also suppressed. The excitatory effects produced by these hormones were potentiated by imidazole. These results suggest that gastrointestinal hormones have a direct excitatory action on the longitudinal smooth muscle of the antrum region and that the excitatory action is associated with phosphodiesterase activity and intracellular cyclic AMP content.