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Biology of Reproduction, Vol 21, 787-792, Copyright © 1979 by Society for the Study of Reproduction
1 Neurosciences Section,
Division of Biology and Medicine,
Brown University,
Providence, Rhode Island 02912 The action of prostaglandin E2 (PGE2) on the response of the circular muscle of the oviductal
isthmus to stimulation of the perivascular, adrenergic nerves was compared in estrous and hCG
treated rabbits. We measured latency from nerve stimulation to evoked potential discharge as well
as the intramural pressure increase reflecting circular muscle contractions. We assume that these
parameters are indirect estimates of the amount of norepinephrine (NE) released during nerve
stimulation. In oviducts from estrous rabbits, PGE2 (10-13 M) increased the latency and decreased
the magnitude of the contraction in response to nerve stimulation but had no effect on spontaneous
myogenic activity or on the sensitivity of the muscle to exogenous NE. Therefore, the inhibitory
actions of PGE2 are probably on the adrenergic nerve terminals within the muscle, resulting in a
decrease in the amount of transmitter released during nerve stimulation. On the other hand, PGE2
(10-13 M) had no effect on the neurogenic responses of oviducts from rabbits 72 h after injection
of hCG. These results suggest that neurogenic contractions of the circular muscle of the isthmus
may become insensitive to the inhibitory effects of endogenous prostaglandin soon after ovulation
occurs. Thus, tonic neurogenic activity could reinforce the spontaneous contractions of the circular
muscle of the isthmus which are believed to mediate ovum transport.
Accepted on July 5, 1979
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