Spread of the single spike activity in the myenteric plexus of the guinea-pig duodenum

The spontaneous single spikes in the myenteric plexus of the guinea-pig duodenum were recorded extracellularly. The myenteric plexus neurones in the cardiac region of the stomach also exhibited the spontaneous single spike activity. The frequency of these spikes was at low level. By the treatment with a high Mg and Ca-free Krebs solution, the single spikes were abolished. The generation of the single spikes was also inhibited by d-tubocurarine. These results suggest the presence of nicotinic neurotransmission in the myenteric plexus. The field stimulation could not evoke the single spike activity. The single spike activities of the myenteric plexus neurones were recorded by two electrodes situated in a ganglion or at two different ganglia. The simultaneous recordings by two different spots showed that there were corresponded and non-corresponded spikes. The former may be due to the conduction of excitation. The values of the correspondence ratio were calculated and the values ranged from 39.1% to 69.6% in a ganglion and ranged from 55.2% to 94.2% in different ganglia. The single spikes may spread over 10 mm in a longitudinal direction. These results suggest that the intra- and interganglionic interactions appear within the myenteric plexus and ganglia are interconnected into a functional integrative circuitry.