Summary
Intracellular microelectrodes were used to analyse the excitatory input to single cells of the mouse vas deferens. Excitatory junction potentials (EJP's) were evoked by both orthodromic and antidromic impulses in terminal axons lying within the musculature of the vas deferens, indicating that transmitter is released from the length of the terminal axon not just from the axon termination. The amplitude of the EJP was altered by altering the strength of stimulation. By using this variation, it was found that 15–22 nerve fibres gave a detectable contribution to the amplitude of the EJP in a single cell. The maximum amplitude of the EJP was 45 mV and the maximum depolarization caused by transmission from a single axon was 5 mV. By depolarizing the whole tissue with noradrenaline, the reversal potential for the EJP was found to be −20 to −15 mV. The EJP was not reversed when a single cell was depolarized with an intracellular current pulse. Extracellular electrodes failed to record any reversal of the EJP, corresponding to current sinks. It is concluded that the EJP in a single cell arises both from the action of transmitter, released from terminal varicosities, on its membrane and from potential changes electrically coupled from adjacent cells via low resistance connections between the smooth muscle cells.
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Supported by grants from the Australian Research Grants Committee and the National Heart Foundation of Australia.
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Furness, J.B. The excitatory input to a single smooth muscle cell. Pflugers Arch. 314, 1–13 (1970). https://doi.org/10.1007/BF00587042
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DOI: https://doi.org/10.1007/BF00587042