Electromyographic activity and noradrenaline content of the rabbit oviduct under different hormonal states.

Spontaneous electromyographic (EMG) activity of the oviduct recorded in vivo in untreated, estrogen-treated, and progesterone-treated castrated rabbits was found to exhibit two main patterns: short spike bursts lasting 1-10 s and long trains of action potentials lasting several minutes, which constituted the major component of EMG activity. After estrogen treatment, both wet weight and noradrenaline (NA) content of the castrated rabbit oviduct were enhanced mainly at the ampullary-isthmic junction; long trains of discharges were significantly shorter (2.0-2.7 min vs 3.6-4.6 min) and appeared at more frequent intervals (9.8-12.2 min vs 14.2-22.6 min). After progesterone treatment, spontaneous EMG activity was not significantly different from that in untreated castrated rabbits (as was the NA content) except at the ampullary-isthmic junction. NA injection elicited a stimulatory response of the oviduct lasting 1-7 min in the three hormonal states. Phentolamine strongly depressed spontaneous EMG activity but the inhibition was more transient in castrated rabbits than in estrogen-treated and progesterone-treated animals. Propranolol had no effect on spontaneous EMG activity. These data and the high NA concentrations found in all parts of the isthmus support the hypothesis that adrenergic innervation plays a role in the organization of oviductal motility in the rabbit.

Preovulatory injection of estradiol-17 beta: effect on noradrenaline activity in different parts of the rabbit oviduct.

This paper compares noradrenaline content in the different parts of the oviduct in rabbits receiving or not a dose of estradiol-17 beta 24 h before human chorionic gonadotropin (HCG) and killed 60 h post HCG. 3,4-Dihydroxyphenylalanine assays were carried out in the oviduct after aromatic L-amino acid decarboxylase was inhibited by m-hydroxybenzylhydrazine (NSD 1015) in the same experimental conditions. Pauerstein et al. (1974) have shown that an intramuscular injection of 250 micrograms of estradiol-17 beta in rabbits 24 h before intravenous injection of 100 IU of HCG delays ovum transport at the ampullary-isthmic junction. The extent of this noradrenergic innervation suggested that estradiol could act at least partially through the noradrenergic systems. Our results show that estradiol-17 beta increased oviduct weight by water retention without modifying either the tyrosine hydroxylase activity or the noradrenaline content in any part of the oviduct and that, consequently, the estrogen-induced "tube locking" of ova was not mediated through the noradrenergic processes.

[In vitro study of the motor activity of two muscle layers in the rabbit oviduct]. / Etude in vitro de l'activité motrice des deux couches musculaires de l'oviducte chez la lapine.

Electrical and mechanical activities in the circular layer in the longitudinal peritoneal muscle were recorded in vitro in the oviducts of untreated and estrogen-treated ovariectomized rabbits. The duration and frequency of the bursts were not significantly changed in either muscle layer by the hormonal treatment. Estradiol increased the propagation of electrical activity in the isthmus and the amplitude of the contractions as well as the synchronization between the mechanical and electrical activities in the two muscle layers. Recordings of both electrical and mechanical activities were necessary to estimate the effects of the estrogen on the muscular layers. Removal of the longitudinal fiber bundles modifying the pattern of electrical and mechanical activities in the circular layer of the isthmus only increased the frequency of circular bursts and the frequency and amplitude of intraluminal pressure changes in both groups of animals. It is supposed that removal of the longitudinal fiber bundles could have damaged the inhibitory isthmic innervation of the circular layer. The EMG activity of the longitudinal layer was generally independent from that of the circular layer in the oviducts of estrogen-treated rabbits. In 24 p. 100 of records which showed a synchronization of the electrical and mechanical activities of both muscle layers in the isthmus, the times between the contractions of the two muscle layers varied from 0.1 to 3.2 sec, suggesting that they were mechanically coupled.