Ionic dependence of electrical activity in small mesenteric arteries of guinea-pigs.
The regulation of blood vessel diameter is under the control of the autonomic nervous system (as well as hormones and metabolites), sympathetic nerve stimulation evoking depolarizing post-synaptic potentials. Excitatory junction potentials (EJPs) were recorded from vascular smooth muscle cells of guinea-pig small mesenteric arteries (pressurized) following nerve stimulation. Repetitive stimulation (greater than 5Hz) led to summation of EJPs, which evoked spikes and vasoconstriction. Replacing extracellular Na+ with choline (plus atropine) resulted in a decrease in EJP amplitude, but spike amplitude and maximum rate of rise (+Vmax) were unaffected. Decreasing the Ca2+ concentration produced decreases in EJP amplitude and spike +Vmax. Verapamil and bepridil, agents that depress Ca2+ influx in vascular and visceral smooth muscle, depolarized the membrane and depressed EJPs and spikes at higher concentrations (10(-5) M and 5 X 10(-6) M, respectively). The data indicate that EJPs are dependent on external Na+ and Ca2+ ions, and that spikes are dependent on Ca2+. Thus, neuromuscular transmission in this muscle is similar to that in non-vascular smooth muscles, such as intestinal muscles and vas deferens.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D004558:Electric Stimulation; D004594:Electrophysiology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008638:Mesenteric Arteries / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000502:physiology* / Q000648:ultrastructure; D009469:Neuromuscular Junction / Q000502:physiology; D012964:Sodium / Q000502:physiology*; D014700:Verapamil / Q000494:pharmacology
D012964:Sodium; D014700:Verapamil; D002118:Calcium