A comparative study of neuromuscular transmission in several mammalian muscular arteries

Intracellular recordings were made from the smooth muscle of isolated segments of the rabbit ear artery, rabbit saphenous artery, rat tail artery, and guinea pig mesenteric artery. Resting membrane potentials recorded from cells in all these arteries were the same (-65 to -75 mV) and perivascular nerve stimulation evoked excitatory junction potentials (EJPs). At stimulation frequencies > 0.2 Hz facilitation of the EJPs was observed in all but the rat tail artery; in this artery the amplitude of the second EJP in a train was less than the first for stimulation frequencies between 0.3 and 2.0 Hz. Spontaneous excitatory junction potentials (SEJPs) at frequencies up to 20/min were recorded during all impalements in the rat caudal artery. In rabbit ear, saphenous and guinea pig measenteric arteries single, supramaximal intensity stimuli evoked EJPs which were not associated with any detectable contraction. Facilitation of EJPs during trains of stimuli > 1 Hz gave rise to graded active responses of up to 50 mV in the saphenous and tail arteries whereas all-or-nothing action potentials of 42--50 mV were recorded in both the rabbit ear and guinea pig mesenteric arteries. Such responses were always associated with contraction. Intraluminal distension of the arteries had no effect on the RMP or response to nerve stimulation.