Interneurons with inhibitory effects on stridulation in grasshoppers exhibit GABA-like immunoreactivity

Three identified descending interneurons (SOG-1, -2, -3) of the suboesophageal ganglion are described that have inhibitory effects on stridulatory movements in the grasshoppers Chorthippus mollis and Omocestus viridulus. No major anatomical or physiological difference has been found between the interneurons of both species. The SOG-1 neuron has a median cell body in the labial neuromere, bilateral symmetrical dendrites and a contralateral descending axon. The SOG-2 and SOG-3 neurons lie in the maxillary neuromere and differ anatomically from each other in an anterior dendritic branch which is present in the SOG-3 neuron. Depolarization of each of the three cells result in a decrease in amplitude or total cessation of the stridulation movement. After the intracellular recordings the neurons were injected with Lucifer yellow and subsequently processed for anti-GABA immunocytochemistry. Each of the neurons shows GABA-like immunoreactivity as revealed on the same section used to identify the location of the cell body.