Gds. Hirst et al., ELECTRICAL-PROPERTIES OF IRIDIAL ARTERIOLES OF THE RAT, American journal of physiology. Heart and circulatory physiology, 42(5), 1997, pp. 2465-2472
When intracellular recordings were made from iridial arterioles, the c
ells had membrane potentials of about -65 mV and perivascular nerve st
imulation evoked a membrane depolarization. When these cells were labe
led with lucifer yellow, all cells that responded to perivascular nerv
e stimulation had the morphological characteristics of smooth muscle c
ells. Cells with the morphological characteristics of endothelial cell
s were never stained. When impaled with two separate recording electro
des, the smooth muscle layer was shown to form an electrical syncytium
with a membrane time constant of similar to 80 ms and an electrical l
ength constant of similar to 900 mu m. At the ultrastructural level, a
reas of close apposition were frequently observed between adjacent smo
oth muscle cells and between adjacent endothelial cells. On the other
hand, at contacts between smooth muscle and endothelial cells, the mem
branes characteristically had much larger separations. The observation
s 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 electri
cally separate.