Effect of strychnine,hydrastine, and apamine on synaptic transmission in smooth muscle cells

The action of strychnine, hydrastine, and apamine on neuromuscular transmission in the stomach and taenia coli was investigated. Hydrastine and strychnine increase nonadrenergic IPSPs of smooth muscle cells. Under the influence of apamine the IPSP and hyperpolarization evoked by exogenous ATP are reversibly blocked and noncholinergic EPSPs appear; ATP, however, does not cause depolarization of the cell membrane. Consequently, apamine is a specific blocker of nonadrenergic inhibition, acting on the postsynaptic membrane, and ATP is a mediator both of this inhibition and of noncholinergic synaptic excitation discovered in smooth muscle cells.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 3, pp. 295–299, May–June, 1978.