Motor reflexes of stomach elicited by phenyldiguanide in the rat

Intragastric pressure (IGP) as an index of gastric motor activity was used to investigate gastric motor responses elicited by phenyldiguanide (PDG) in rats under pentobarbitone anaesthesia. Phenyldiguanide injected into the atrium produced an inhibitory gastric motor response whereas an aortic injection resulted in an increase in IGP. Intracarotid injections were without effect. Atropine reduced the response to atrial PDG but not to aortic PDG. Cervical vagotomy abolished the response to both atrial and aortic PDG. Guanethidine and spinal transection abolished the response to atrial PDG only. It is concluded that PDG acts by stimulation of nonmedullated vagal afferents. The efferent pathway for PDG-evoked gastric relaxation is through sympathetic nerves and the efferent system for gastric contraction involves a noncholinergic, nonadrenergic excitatory mechanism.