Pharmacological properties of electrical activities obtained from neurons in Auerbach's plexus.

Two kinds of spikes, a single-spike unit and burst unit, were obtained by a glass suction electrode recording from neurons in Auerbach's plexus of the guinea pig ileum. Both spikes were inhibited by tetrodotoxin but not by Mn2+. Frequency of the single-spike unit was increased by nicotine and high concentrations of acetyl choline. The single-spike unit induced by nicotine was inhibited by hexamethonium, while hexamethonium was without any effect on the spontaneous single-spike unit. Morphine inhibited the spontaneous single-spike unit. The spontaneous single spike unit was also inhibited by a-adrenergic stimulants but not by β-adrenergic stimu lants. Inhibition of single-spike unit activity by the α-adrenergic stimulants was antagonized by α-adrenergic blockers. These findings indicate that the single-spike unit is concerned with cholinergic transmission in Auerbach's plexus. The single spike unit evoked by nicotine was partly inhibited by morphine or α-adrenergic stimu lants. This fact indicated the possibility that morphine and the α-adrenergic stimu lants also inhibit the acetylcholine release from the cholinergic nerve at the ending of the post-ganglionic fibres. On the other hand the burst unit was little affected by the drugs utilized herein. The effects of drugs on acetylcholine liberation from the ileum of the guinea pig have been extensively studied by many authors (1-11), however, pharmacological experiments on the electrical activities from neurons in Auerbach's plexus are rare. Recently, the elec trophysiological properties of Auerbach's plexus have received considerable attention. The present paper describes the effects of some drugs on electrical activities obtained by a fine glass suction electrode recording from neurons in Auerbach's plexus of the guinea