Allatotropic peptides modulate muscle contraction of the female reproductive system in Rhodnius prolixus (STÄL).

Allatotropin (AT) acts as a myoregulator at the level of the dorsal vessel (DV) and midgut (MG) in triatominae insects. Previous analyses of the expression of the AT receptor in Rhodnius prolixus showed that AT is expressed in the DV and MG, but also in the reproductive system in females. To further study the activity of AT on female reproductive organs we analyzed the response by adult females in different physiological conditions, including unfed (virgin and mated), and fed mated females (gravid), to doses ranging between 10-14 and 10-6M. Myoregulatory activity was evaluated in vivo, by recording independently the frequency of contractions of each organ after treatment. The results show that the effect of AT varies depending on the organs and on the physiological state of the female. Whilst unfed virgin females did not show response to the peptide for neither of the applied doses, the ovaries showed a differential response, presenting the highest frequency of contractions in gravid individuals. An increase in the frequency of contractions of the oviducts was only observed in mated females. Uterus and spermathecae responded in both gravid and mated females, with maximum activity in the latter. In the bursa, responses were only detected in gravid females. The differential response of the organs seems to be associated to particular moments along the reproductive cycle, such as with the spermathecae that reacted to AT in both unfed mated and gravid females, when the movement of spermatozoids is physiologically crucial. Testes and accessory glands of the male, expressed the mRNA of AT precursor, suggesting that the male would modulate the contractile behavior of the female reproductive system after copula. The ovaries also expressed AT mRNA suggesting the existence of a paracrine/autocrine system modulating muscle contraction.