The Role of Octopamine and Tyramine in the Adult Female Reproductive System of Rhodnius prolixus

Octopamine and tyramine are neuroactive chemicals involved in many physiological processes acting as neurotransmitters, neuromodulators and neurohormones. Octopamine and tyramine modulate reproduction in insects. In Rhodnius prolixus, octopamine decreased the amplitude and reduced the RhoprFIRFa-induced oviduct contraction in a dose-dependent manner, whereas tyramine only reduced the RhoprFIRFa-induced contractions. Also, octopamine and tyramine reduced the frequency and abolished bursal contractions at higher concentrations. Octopamine also increased the levels of cAMP in the oviducts, an effect blocked by phentolamine. Dibutyryl cAMP mimicked the effects of octopamine at the bursa, suggesting that octopamine may act by an Octβ-receptor, a known GPCR. The cDNA sequences of RhoprOctβ2-R and RhoprTyr1-R have been cloned and characterized; the receptor transcripts are expressed in all female reproductive tissues. Injection of octopamine and tyramine into mated and fed adult females increased oogenesis. Overall, octopamine and tyramine modulate the female reproductive tissues leading to successful laying of eggs.M.Sc