Some properties of the smooth muscle of mouse vas deferens.

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Abstract
Contractions of the mouse vas deferens in response to electrical stimulation differ from those recorded from the guinea pig vas deferens in that they were abolished by tetrodotoxin. Changes in membrane potential were recorded from the smooth muscle of both preparations in response to stimulation with current pulses applied by an intracellular electrode and by large extracellular plate electrodes. Both preparations behaved similarly in response to intracellular stimulation. Electrotonic potentials in response to extracellular current pulses spread in a longitudinal direction in the guinea pig vas deferens in accordance with the cable-like properties of this preparation. No longitudinal spread of electrotonus was observed in the mouse vas deferens. Responses to nerve stimulation differed in the 2 preparations. In the guinea pig, single stimuli caused excitatory junction potentials (ejp) which gave rise to action potentials. Some cells from the mouse vas deferens showed similar ejp and action potentials, although the threshold for the initiation of action potentials was lower and more variable. The majority of cells in the mouse vas deferens failed to show action potentials in response to a single stimuli even though the amplitude of ejp was from 35-40 mV. This was probably due to the large resting membrane potential of these cells, as all-or-nothing action potentials could be evoked if successive ejp were allowed to sum with each other or if a depolarizing current pulse was applied at the peak of an ejp. The nature of the response to nerve stimulation recorded from different cells in the mouse vas deferens was correlated with the amplitude and time course of the response of the same cell to intracellular stimulation. Individual smooth muscle cells in both preparations were probably coupled electrically but that there were few, if any, low resistance pathways in the longitudinal direction in the mouse vas deferens.