Spontaneous Electrical Activity in Pressurized Small Mesenteric Arteries

Abstract

Spontaneous electrical activity was recorded intracellularly in vitro from smooth muscle cells of guinea pig small pressurized mesenteric arteries. Spontaneous action potentials were recorded at 37 °C at frequencies of 30–55/min. Each action potential consisted of a prepotential (pacemaker potential) followed by a spike of variable amplitude (10–35 mV). This activity was not blocked by tetrodotoxin (TTX) or guanethidine, indicating it was myogenic in origin. Sympathetic nerve stimulation (single 0.5-ms field stimuli) could evoke action potentials in between the spontaneous action potentials and could drive the activity; this effect was blocked by TTX. Addition of the vasodilator adenosine (10^–6 to 10^–4 M) reversibly decreased action potential amplitude and frequency. Lowering the temperature to 35 °C for 1–3 min during a single impalement decreased spontaneous action potential frequency. Spontaneous activity was abolished after longer periods at 35 °C. The spontaneous activity recorded in vitro at 37 °C and 5 or 40 mm Hg inflation pressure was similar to that previously reported from guinea pig and rat mesenteric arteries in vivo. Such activity might be important in the normal physiological control of arterial tone.