Effects of sympathomimetic drugs on the contractility of the vas deferens and on fertility in the male rat and rabbit

The sympathomimetic drugs noradrenaline, methoxamine, tyramine and norephedrine, caused rhythmic contractions in isolated human vasa deferentia. These contractions were mediated via α-adrenorcceptors. Intravenous administration of some of these drugs into rats and guinea-pigs produced contractions of the vas deferens in vivo but was accompanied by severe cardiovascuiar side effects. Hence a local method of application, using medical grade silastic in the form of collars or rods was developed. Insertion of fhese slow-releasing devices around the vas deferens in anaesthetized rats produced rhythmic contractions without serious side effects. In a fertility screen, these silastic drug mixtures caused a temporary reduction in fertility of male rats and rabbits. The maximal antifertility action occurred in the first week foIlowing the insertion of drug-containing collars or rods. At the time of the peak effect on fertility, the numbers of sperm in the ejaculate were reduced to almost zero. In addition the treatment impaired the quaIity of the ejaculated sperm. Spontaneous restoration of fertiIity was evident with some of the treatments, but not with others. It was concluded that the main cause of infertilty was the reduction of sperm numbers in the ejaculate resulting from either a block in sperm transport in the vas deferens or by a deficiency in the mechanism of emission. An occlusion of the vas may result from a mechanical block as with methoxamine or from a sustained spasm. A defect in emission may result from depletion of the transmitter, receptor-specific desensitization or by pre-synaptic α-receptor mediated inhibition.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral-pg

Grantor dc:publisher.institution

University of Strathclyde

Year dc:date.issued

1978

Author dc:creator

• Ratnasooriya, W. D.

DOI

10.48730/bgyt-2m39

Identifier

uk.bl.ethos.470033
T3369

OAI identifier oai:identifier

oai:strathclyde:c821gj795