Effect of long‐term treatment with high doses of guanethidine on sperm transport and fertility of rats

Abstract

Summary Male rats treated with guanethidine 25 mg/kg daily for eight weeks had no demonstrable ejaculatory function immediately after cessation of treatment. Four weeks later, ejaculatory function had returned in two‐thirds of the males, and after eight weeks, all males were able to deposit sperm in the vagina. However, fertility had returned at that time in only two of the nine males. On the basis of these findings it might be expected that fertility would return in the other males after a more prolonged observation period. At autopsy, 66 days after cessation of treatment, the vasa deferentia were congested and filled with viscous material, and along their course dilated regions and pseudocysts containing sperm debris and spermatozoa were found. The isolated ducts of the guanethidine‐treated males showed a markedly increased response to noradrenaline if compared with ducts from control rats. Response to tyramine was similar in both treated and untreated rats. In view of the increased response to noradrenaline it may be concluded that the noradrenaline stores, which are sensitive to tyramine, were still reduced 66 days after guanethidine treatment had been stopped.

Guanethidine and Guanacline on the Rat Vas Deferens

“…However, chronic treatment of rats with guanethidine (10 mg/kg) for 13 weeks has recently been shown not to decrease the number of axons nor to produce any degenerating axons in the vas deferens (Evans, Iwayama & Burnstock, 1973). Although these authors reported no restoration, after cessation of treatment, of contractile responses to stimulation previously blocked by guanethidine treatment, Hepp & Kreye (1973) did find that ejaculatory function was restored 8 weeks after guanethidine treatment had finished (25 mg/kg daily for 8 weeks). The latter result agrees with the findings in the present study where contractile responses were partly restored after cessation of guanethidine treatment.…”

Contractile Behaviour of Rat Epididymis after Sympathectomy Produced by the Administration of Guanethidine

“…This is not the case concerning the smooth muscle of other organs, where the action of adrenergic and cholinergic fibers are opposed to each other. The fact that treated rats were able to ejaculate after mating (Hepp and Kreye -1973) or after electroejaculation, indicates that, although this obstruction cannot be avoided by an increased spontaneous activity, it can be overcome by the sudden contractions that take place during ejaculation. In our experiments the persistence of spontaneous motility in the ductus and the presence of spermatozoa in the ejaculate after electroejaculations, allows us to assume that cholinergic neurotransmission acts directly on the smooth muscle of the epididymis in absence of adrenergic innervation.…”

A STUDY OF STIMULATION‐EVOKED ACTIVATION OF α2‐ADRENOCEPTORS IN THE RAT ISOLATED VAS DEFERENS

“…It has been suggested previously that regional variation along the length of the vas deferens of responsiveness to field stimulation and to noradrenaline may be of functional significance (Pennefather et al, 1974). Within the vas deferens, sperm are transferred in an epididymal to prostatic direction, and there is evidence to suggest that this transport is regulated by sympathetic activity both during and in between periods of sexual activity (Evans et al, 1972;Hepp & Kreye, 1973;Prins & Zaneveld, 1969;Zankl & Leidl, 1979 ; Alexander et a/., 1979). In the dog vas deferens hypogastric nerve stimulation in vivo produces a delayed co-ordinated contractile response which occurs first in the epididymal end and is followed 5-10 s later by contraction at the prostatic end of the tissue (Kimura ef ul., 1975).…”