Some properties of the excitatory junction potentials recorded from saphenous arteries of rabbits.

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Abstract
Excitatory junction potentials (EJP) were recorded from smooth muscle cells of the saphenous arteries of young rabbits. EJP amplitudes recorded from different preparations, in response to a single maximal stimulus, were small and variable (5-14 mV) and decayed exponentially with a time constant of .apprx. 200 ms. At frequencies > 1 Hz the shape of EJP exceeding 12-15 mV in amplitude was changed. The velocity of the early part of the EJP increased. Trains of up to 5 stimuli at frequencies > 4 Hz caused summation of EJP; active responses were superimposed on depolarization. Peak amplitude of the response to repetitive stimulation was 50 mV. In isotonic solution, contraction appeared to be associated with a change in configuration of EJP. No action potentials resembling those recorded from most visceral smooth muscles were observed in isotonic solutions although these could be evoked by TEA [tetraethylammonium] (2.5-10 mM). The Abe and Tomita method was used to determine values of the length constant (.lambda.) and time constant (.tau.) of the smooth muscle of intact arteries. The value of .lambda. (0.6 mm) was .apprx. 1/2 that for circular strips cut from larger arteries. The time constant of decay of single EJP of < 12 mV in amplitude was indistinguishable from the membrane time constant. Noradrenaline [norepinephrine] caused contraction of the artery in the absence of a change in membrane potential. There may 2 different populations of receptors in this smooth muscle membrane.