The membrane potential of the Japanese quail's oviductal smooth muscle during ovum transport

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Abstract
In the quail''s oviductal smooth muscle there evidently exists coordinated electrical and mechanical activity. It is not known how the contractions are regulated; the oviduct probably functions as a stretch receptor and the mechanical stimulus is produced by the ovum itself. The cellular basis for stretch-induced contractions is not known. In strips (8) from the magnum, stretches of 50% changed the membrane potential. Compared with the resting length L0 (= 100%), stretches to 150% and 200% significantly (P < 0.001) hyperpolarized the membrane potential. Analyses of variance, revealed that at the length 150% both the level of stretch and single experiments differed significantly in relation to the membrane potential: F = 7.1, P < 0.5; F = 14.6, P < 0.01, respectively. At the length 200%, there were highly significant differences between the groups 100% and 200% (F = 36.3, P < 0.01) but the differences could be explained by the highly significant (F = 13.9, P < 0.001) interaction. Membrane potential measured from isolated, intact oviducts (7) which had ovum in the magnum was significantly depolarized by 8-9 mV on the region over the ovum. The membrane potentials were the same in the different segments of the oviduct which did not contain an ovum: 52 mV. At fiber level, the temporal and spatial changes in membrane potential could be the basis for the stretch receptor characteristics of the quail''s oviductal smooth muscle which has been concluded to be responsible for ovum transport.