Dopamine regulation of reproduction in insects

Dopamine (DA) regulates reproductive behavior and promotes maturation of the reproductive system in insects. In Drosophila , male courtship behavior is regulated by the protocerebral posteriolateral dopaminergic cluster neuron 2ab (PPL2ab). The ability to synthesize DA in the PPL2ab affects male-male and male-female courtship behavior. The DA level in the brain of adult male Drosophila influences sexual orientation; although, male-male courtship is induced when the DA level is too high or too low. DA also regulates changes in reproductive behavior and post-copulation behavior. As a neurohormone, DA regulates taste and smell perception in insects. In the central nervous system, DA regulation of reproductive behavior involves the DA/MH (molting hormone) receptor (DopEcR) and synergy between DA and ecdysone, with the tritocerebrum P1 neurons playing an important role in the male courtship information loop. DA can promote development in the eggs and regulate the reproductive state in social insects. The promotional effect of DA on egg development involves developmental stage differences in DA receptor expression and interactions among DA, juvenile hormone (JH), MH, and octopamine (OA). For example, the expression level of dopamine D2-like receptor (DD2R) in the corpora allata of D. melanogaster young females is far lower than that in sexually mature females. Meanwhile, the expression level of dopamine D1-like receptor (DopR) in young females is much higher than that in mature females. By contrast, the expression of DopR and DD2R in the fat body is the opposite to that in the corpora allata. The interactions among DA, JH, MH, and OA depend on the expression of certain genes and regulation of metabolic enzyme activity. In addition, the interactions among different hormones also involve the insulin-like signaling (ILPs) pathway. As to reproductive state regulation in social insects, it has been found that the reproductive state of worker bees is regulated by queen mandibular pheromone (QMP), larvae pheromones, and the ovarian DA D2 receptor gene. Research on DA regulation of insect reproduction will provide us with references for the development of new drugs, and for research on mechanisms in human brain science and nervous system diseases.