Effect of various drugs and extrinsic denervation on the non-adrenergic inhibitory neurons in the rat stomach.

The effects of various drugs and extrinsic denervation on the non-adrenergic inhibitory nerves in the rat stomach were examined. Stimulation of the intramural nerves supplying the longitudinal smooth muscle strips taken from the rat stomach produced responses consisting initial contractions followed by relaxations in the presence of guanethidine in case of the tone of the preparation maintained with serotonin. After scopolamine treatment, transmural nerve stimulation (TMS) caused a relaxation or a relaxation followed by a transient after-contraction. All of these responses were abolished reversibly with tetrodotoxin. After cold storage of rat stomach strips for 5 d at 4 degrees C, the TMS-induced response was not observed, but noradrenaline still relaxed these strips. The TMS-induced relaxation reached a maximum amplitude at 2-5 Hz, and was entirely independent of alpha- and beta-blockers, or a combination of them. It was not affected by treatment of 6-hydroxydopamine and reserpine. These results strongly suggested that the relaxation was not myogenic, but neurogenic, and was not elicited by stimulation of adrenergic neurons. Strychnine and poly-L-lysine inhibited the relaxation elicited by TMS even in normal and transection-treated rats. Histochemical studies showed degenerative changes due to the dissection at the axons of a ganglion in the Auerbach's plexuses by transection. The effect of various drugs and extrinsic denervation on the response to TMS in relation to non-adrenergic inhibitory nerves in the rat stomach is discussed.