Differential modulation of bovine epididymal activity by oxytocin and noradrenaline

Abstract

Passage of spermatozoa through the epididymis and emission of sperm during ejaculation are based on spontaneous and induced contractions of epididymal peritubular muscle layers. This study deals with the ejaculation-relevant factors noradrenaline (NA) and oxytocin (OT) and their contractile effects in the course of the bovine epididymal duct. Muscle tension recording revealed excitatory effects of NA in all duct regions. A peculiarity was found in a duct section between the mid-cauda and ductus deferens, where the responsiveness to NA was particularly faint in comparison with the adjacent regions. NA-induced contraction was primarily mediated by postjunctional a 2 -adrenoceptors (ADRA) in the caput and corpus regions, and by a 1 -ADRA in the cauda region. Contrary to NA, OT exerted regionally varying effects. The peptide induced contraction in intact and epithelium-denuded caput as well as in epithelium-denuded corpus segments but had a relaxant net effect in intact corpus and proximal cauda segments. Within the mid-cauda, OT evoked strong contraction, which progressively decreased distally. Receptor specificity of the epididymal OT effects was verified using the selective OT receptor (

Time-Lapse Imaging as a Tool to Investigate Contractility of the Epididymal Duct – Effects of Cgmp Signaling

“…As suggested before for different species [16], [24], [25], [27], [28] we observed a regular and phasic contractile activity in duct segments of all parts investigated in the caput and corpus regions. Direct information on contractile force, however, cannot be deduced directly by our experiments.…”

“…This was neither possible by previously used visual studies [3], [24] nor by pure physiological settings [15], [16], [25], [26] and it was interesting to see that the frequency of spontaneous contractions remained stable over the length of one isolated part of the epididymal duct.…”

Erg K+ channels modulate contractile activity in the bovine epididymal duct

“…OT (500 nM), which was recently found to evoke strong contraction in the epididymal cauda region (24), was applied at the end of each experiment to check intactness of the epididymal musculature. To test the ability of E-4031 to affect contraction in the cauda (m), the channel blocker was applied after application of OT (500 nM).…”

Physiological and pharmacological impact of oxytocin on epididymal propulsion during the ejaculatory process in rodents and men

“…A relaxing effect was noted in cow corpus and proximal cauda epididymidis. 22 One study found no electrical or mechanical effects of oxytocin on rat caput or cauda epididymidis. 27 In rat and rabbit epididymis (without specifying which part exactly) another study reported oxytocin to have no effect 28 but found vasopressin (which differs to oxytocin only by two amino acids) to have an increasing effect, suggesting that the vasopressin 1 A receptor rather than the oxytocin receptor might be involved in signal transduction of oxytocin in the epididymis.…”