Burst generation in coordinating interneurons of the ventilatory system of the locust
- Cite this article as:
- Pearson, K.G. J. Comp. Physiol. (1980) 137: 305. doi:10.1007/BF00657111
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Intracellular recordings were made from the processes of the interneurons coordinating ventilatory pumping movements in two species of locust,Schistocerca gregaria andLocusta migratoria. These neurons have their cell body in the metathoracic ganglion and their axon extends to the last abdominal ganglion via the contralateral abdominal connective. The structure of these interneurons within the metathoracic ganglion was determined by intracellular staining with cobalt followed by Timm's intensification, or by the injection of the fluorescent dye Lucifer Yellow.
During expiration the coordinating interneurons receive a large excitatory synaptic input causing them to discharge in an accelerating burst. Within the interburst interval no inhibitory postsynaptic potentials were observed, and excitatory postsynaptic potentials occurred only occasionally.
A number of tests failed to demonstrate that the coordinating interneurons were endogenous bursters, or that there was any coupling between different coordinating interneurons. Thus, bursts in these interneurons appear to be produced entirely by periods of intense excitatory synaptic input from as yet unidentified interneurons.
The rate of ventilation could be increased by a factor of two by the intracellular injection of constant depolarizing current into a coordinating interneuron. Although this result indicates that the coordinating interneurons are elements within the ventilatory rhythm generating system, it is probable that they are normally involved in generating the rhythm only when the demand for oxygen is high.