Article date: December 1988
By: Seiichi Komori, Hidenori Ohashi in Volume 95, Issue 4, pages 1157-1164
Changes in membrane potential in response to local application of ATP by pressure ejection from a micropipette were recorded intracellularly from smooth muscle cells of the longitudinal muscle strip of chicken rectum.
The local application of ATP produced a membrane depolarization. The depolarizing response increased to a plateau of 33 mV with prolongation of the duration of pressure pulses which determines the amount of ATP ejected. The latency and the time required to reach a peak depolarization were not related to the pulse duration, and the shortest latency was 50 ms.
When the application of ATP was repeated at a short interval, the second and subsequent depolarizing responses were suppressed, and their latency and time to reach a peak were also increased; the muscle cells became desensitized to ATP. Recovery from the desensitization occurred slowly over a period of 60s.
Electrotonic potentials decreased in amplitude and time course during an ATP‐induced depolarization, indicating a decrease in membrane resistance.
The ATP‐induced depolarization was longer in the latency than an excitatory junction potential (e.j.p.) elicited by electrical field stimulation of the intramural nerves. The other variables such as amplitude, time to reach the peak and duration could not be matched with those of the e.j.p. at the same time.
The e.j.p. decreased in amplitude and duration during the ATP‐induced depolarization, and its initial amplitude and duration were restored immediately after termination of the ATP‐induced depolarization, as in the case of electrotonic potentials. The e.j.ps were recorded in the same manner as the control from the muscle cell which was in a state of desensitization to ATP.
The present results provide an argument against the hypothesis that ATP mediates the e.j.p. in the rectum of the chicken.
Changes in membrane potential in response to local application of ATP by pressure ejection from a micropipette were recorded intracellularly from smooth muscle cells of the longitudinal muscle strip of chicken rectum.
The local application of ATP produced a membrane depolarization. The depolarizing response increased to a plateau of 33 mV with prolongation of the duration of pressure pulses which determines the amount of ATP ejected. The latency and the time required to reach a peak depolarization were not related to the pulse duration, and the shortest latency was 50 ms.
When the application of ATP was repeated at a short interval, the second and subsequent depolarizing responses were suppressed, and their latency and time to reach a peak were also increased; the muscle cells became desensitized to ATP. Recovery from the desensitization occurred slowly over a period of 60s.
Electrotonic potentials decreased in amplitude and time course during an ATP‐induced depolarization, indicating a decrease in membrane resistance.
The ATP‐induced depolarization was longer in the latency than an excitatory junction potential (e.j.p.) elicited by electrical field stimulation of the intramural nerves. The other variables such as amplitude, time to reach the peak and duration could not be matched with those of the e.j.p. at the same time.
The e.j.p. decreased in amplitude and duration during the ATP‐induced depolarization, and its initial amplitude and duration were restored immediately after termination of the ATP‐induced depolarization, as in the case of electrotonic potentials. The e.j.ps were recorded in the same manner as the control from the muscle cell which was in a state of desensitization to ATP.
The present results provide an argument against the hypothesis that ATP mediates the e.j.p. in the rectum of the chicken.
DOI: 10.1111/j.1476-5381.1988.tb11751.x
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