Intersegmental Thoracic Descending Interneurons in the Cockroach Periplaneta americana

Abstract

The number, location and morphology of intersegmental descending interneurons, which connect pro- and mesothoracic ganglia with the matathoracic ganglion in the cockroach Periplaneta americana, were investigated herein using a retrograde nickel chloride tracing through one of the connectives that link meso- and metathoracic ganglia. The bodies of stained neurons were aggregated into clusters lying ether ipsilaterally or contralaterally to the axon through which the dye was delivered. Differences in size, architecture and dendrite ramification of ipsi- and contralateral neurons were described. Ipsilateral neurons ramified also ipsilaterally, whereas contralateral neurons formed ramifications on the both sides of the ganglion. The data obtained suggest that adjustment of the walking pattern generator by sensory input from legs is mainly achieved through ipsilateral descending neurons, while adaptation to the environment and brain commands is accomplished through contralateral neurons.