Modification of the response to nerve stimulation in small arteries of guinea-pig caused by distension of the artery.

1. Intracellular recordings of membrane potential were made from the smooth muscle of small arteries taken from the guinea-pig ear. The arteries were internally perfused at constant pressures ranging from 0 to 60 mmHg. 2. The resting membrane potential of the smooth muscle was not affected by altering the perfusion pressure. 3. At the higher pressures the smooth muscle membrane showed an enhanced ability to generate rapidly rising action potentials. 4. The amplitude of the excitatory junction potential evoked by a single stimulus to the perivascular nerves was increased when the perfusion pressure was raised. 5. Excitatory junction potentials and action potentials could be recorded in the presence of tetrodotoxin (3 x 10(-6) M) although increased stimulus voltages were required. These responses were abolished by guanethidine (2 x 10(-5) M). 6. The effects of increased perfusion pressure could still be observed in tetrodotoxin.