From molecule to sexual behavior: The role of the neuropentapeptide proctolin in acoustic communication in the male grasshopper Chorthippus biguttulus

Acoustic communication in male Chorthippus biguttulus is a suitable behavioral model to explore the physiological effects and underlying molecular mechanisms of identified neuropeptides. Proctolin plays a modulatory role in a neuronal circuit controlling sexual behavior in these insects. Activation of proctolin receptors triggers courtship singing (the second level of excitation in sexual behavior) that is preceded by call singing triggered by muscarinic acetylcholine receptor activation. The pharmacological studies presented here revealed that the Phospholipase C pathway was involved in courtship singing since neomycin and Li+ strongly inhibited proctolin-stimulated singing. In addition, injecting phorbol ester into proctolin-sensitive neural sites only elicited stridulation. This confirms that proteinkinase C can mediate the effects of Phospholipase C activation in this model. These results partially clarify the molecular mechanisms in the decision making brain center that controls sexual behavior in these insects.