Neurochemical control of cricket stridulation revealed by pharmacological microinjections into the brain.

Neuroactive substances were administered into the frontal protocerebrum of tethered male Gryllus bimaculatus by pressure injections from microcapillaries. All three types of species-specific song pattern (calling song, rivalry song and courtship song) could be elicited by injection of acetylcholine and cholinergic agonists. Injection of nicotine led to short bouts of calling song that occurred after a short latency. In contrast, muscarine elicited long-lasting stridulation that took longer to develop. The pharmacologically induced song patterns showed transitions from rivalry song to calling song and from calling song to courtship song, which also occur during natural behaviour. Stridulation induced by a cholinergic agonist could be immediately blocked by microinjection of (&ggr;)-aminobutyric acid (GABA) into the same neuropile sites. Administration of picrotoxin in resting crickets led to enhanced motor activity that incorporated the three different song patterns. We propose that, in the brain of the cricket, acetylcholine and GABA are putative transmitters involved in the control of stridulation. Histological analysis located the stimulation sites to an area between the pedunculus and the (&agr;)-lobe of the mushroom body in which the command neurons for calling song have dendritic arborizations.