Glutamate and neuropeptide released in the brain of male grasshopper Chorthippus bigutulus alter the contex of the produced singing in a step-wise manner
Injections of neuropeptide proctolin into brain can elicit singing behaviour in male grasshoppers of the species Ch.biguttulus. It has been shown earlier that activation of mAChRs lead to prolonged calling song – fi rst level of excitation. Proctolin release might be associated with courtship singing and could probably trigger switches between calling and courtship singing when a con-specifi c female responds acoustically – second level of excitation. Coinjections of proctolin with glutamate could alter the time course of proctolin-stimulated singing by appearance of precopulatory movements or led to appearance of additional behaviours such as wing fl appings – third level of excitation. The singing patterns are produced only by the hind legs stridulatory movements rubbing to the wing’s vein and driven by internal neuronal oscillator. The context of the acoustic patterns depends only on the time courses of these hind legs’ movements. The arousal of excitation was not linear but in a step-wise manner alternating the described patterns above. These pattern alterations were triggered by co-release of few neurotransmitters – ACh, proctolin and glutamate. There were indications that the intracellular signalling pathways coupled to mAChRs, Proctolin receptors and mGluRs interact each other to achieve the switches between the particular oscillator activity. The latter might alternate the outgoing message context, produced by the male in a given communicative situation.