Electrical synapses on the axon form spontaneous burst activity of the Retzius neuron of the leech

Abstract

The purpose of this article was to demonstrate the variation of impulse activity of a neuron when electrical synapses (ES) appear on its branches. The object of research was an abdominal nerve ganglion of a medical leech. Spontaneous impulse activity of one of the neurons on the surface of a ganglion was registered. In order to obtain ES we used 0.4% pronase solution to transform the ganglion into a new nerve structure, namely, a glial-free ganglion. We studied impulse activity frequency, amplitude and the duration of spikes of an individual neuron. It was found that in the glial-free ganglion, the neuron generates a burst of impulses. The duration of the first impulse in the burst is equal to the duration of a spontaneous spike of a neuron, usually (6.00±0.86 ms and 5.95±0.29 ms), and the duration of subsequent impulses in the burst is equal to 2.45±0.5 ms. A gradual drop in the amplitude and a change in the duration of impulses in the burst is a typical sign of reverberation. Using a graphical model, we have attempted to demonstrate the way in which a chain of ES between neuronal processes in a ganglion can generate reverberant activity in one cell without involving the soma of other cells. The graphic model shows the processes underlying this reaction. Thus, both the experimental and theoretical analysis of such a simple model of nervous tissue as the modified ganglion of an abdominal nerve chain of the leech demonstrates the diversity and undiscovered possibilities of ES contribution to the neural mechanisms of the nervous system.