Opposite effects of ecdysone and 20-hydroxyecdysone on in vitro uterus motility of a tsetse fly

In order to examine the possible effects of ecdysteroids on parturition, we studied in vitro the influence of ecdysone and 20-hydroxyecdysone on the motility of isolated uterus from virgin and pregnant female tsetse fly (Glossina fuscipes). Ecdysone initiates phasic uterine contractions or enhances the frequency of preexisting contractile activity. In contrast, uterine contractions are decreased or abolished by 20-hydroxyecdysone. Pharmacological data indicate that tsetse fly uterus exhibits myogenic and nerve-evoked contractions. Ecdysteroids mainly act on nervous structures that control muscle contractions. Our results provide evidence for a specific action of ecdysteroids on a nerve-muscle target involved in female reproduction.