Activity of metathoracic interneurons during stridulation in the acridid grasshopperOmocestus viridulus L.

Abstract

1. The activity of metathoracic interneurons of the acridid grasshopperOmocestus viridulus L. was recorded intracellularly while the animals were caused to stridulate by electrical stimulation of the prothoracic ganglion. After recording, the interneurons were injected with the fluorescent dye Lucifer Yellow to reveal their structure. To monitor the stridulation pattern the muscular activity during stridulation was documented by myograms recorded extracellularly from metathoracic muscles (Fig. 1). 2. Five types of unisegmental interneurons discharged in a pattern coupled to the pattern of muscular excitation in singing (Figs. 2–7). Interneurons of each of the five types resembled the stridulatory pattern such that certain phases of their activity were highly correlated with the onset of the contraction in the stridulatory muscles (Table 1). 3. The activation of these interneurons within the stridulatory rhythm distinctly preceded that of the musculature (Figs. 2, 5), and the neurons responded hardly at all to sensory stimuli. For these reasons, it is assumed that the interneurons are not activated by sensory inputs during stridulation. 4. In a not stridulating grasshopper depolarization caused some of the interneurons to discharge bursts of impulses that closely resembled the pattern of excitation during stridulation (Fig. 8).