Some characteristics of transmission from non-adrenergic, non-cholinergic excitatory nerves to the smooth muscle of the chicken.

Non-adrenergic, non-cholinergic excitatory junction potentials (e.j.p.s) were recorded from the longitudinal muscle cells of the chicken rectum following stimulation of the nerve of Remak and field stimulation of intramural nerves. The amplitude of e.j.p.s was a direct function of the stimulus intensity. When peak depolarization of an e.j.p. reached threshold, a muscle action potential was evoked. When the extrinsic nerve was stimulated with a given stimulus intensity, the e.j.p.s recorded from different cells showed little change in amplitude and time-course, reached their peaks in 74 ms and declined to half their amplitudes in 230 ms. These corresponding values for the e.j.p.s in response to field stimulation were 51 ms and 159 ms respectively, but became larger as the microelectrode was moved away from the stimulating site. The amplitude became smaller also and the distance at which the e.j.p. declined to half its control amplitude was 4.3 mm. The time constant for the exponential decay phase of the e.j.p. was the same as the time constant for the muscle membrane. Facilitation of e.j.p. amplitude occurred during repetitive nerve stimulation; however, the facilitation was accompanied frequently by an initial depression phase during extrinsic nerve stimulation.