Electrical properties of iridial arterioles of the rat

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 273; no. 5; pp. H2465 - H2472
• Main Authors: Hirst, G. David S, Edwards, Frank R, Gould, Dianna J, Sandow, Shaun L, Hill, Caryl E
• Format: Journal Article
• Language: English
• Published: United States 01.11.1997
• Subjects: Animals; Arterioles - innervation; Arterioles - physiology; Arterioles - ultrastructure; Electric Stimulation - methods; Endothelium, Vascular - physiology; Endothelium, Vascular - ultrastructure; Iris - blood supply; Membrane Potentials - physiology; Muscle Contraction; Muscle, Smooth, Vascular - innervation; Muscle, Smooth, Vascular - physiology; Muscle, Smooth, Vascular - ultrastructure; Rats; Sympathetic Nervous System - physiology
• ISSN: 0363-6135; 0002-9513; 1522-1539; 2163-5773
• DOI: 10.1152/ajpheart.1997.273.5.H2465

1  Department of Zoology, University of Melbourne, Parkville, Victoria 3052; and 2  Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 0200, Australia When intracellular recordings were made from iridial arterioles, the cells had membrane potentials of about 65 mV and perivascular nerve stimulation evoked a membrane depolarization. When these cells were labeled with lucifer yellow, all cells that responded to perivascular nerve stimulation had the morphological characteristics of smooth muscle cells. Cells with the morphological characteristics of endothelial cells were never stained. When impaled with two separate recording electrodes, the smooth muscle layer was shown to form an electrical syncytium with a membrane time constant of ~80 ms and an electrical length constant of ~900 µm. At the ultrastructural level, areas of close apposition were frequently observed between adjacent smooth muscle cells and between adjacent endothelial cells. On the other hand, at contacts between smooth muscle and endothelial cells, the membranes characteristically had much larger separations. The observations show that individual smooth muscle cells are electrically coupled to their neighbors, but the morphological studies raise the possibility that in these arterioles the endothelial and muscle layers are electrically separate. endothelial cells; smooth muscle syncytium; ultrastructure; electrical coupling