Physiological and Morphological study on the humidity-information processing in insect CNS

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Though there have been a number of electrophysiological and morphological studies on insect hygroreceptors, there is no paper about properties on interneurons in the CNS of insects responding to numidity changes. We recorded electrical activities to humidity changes from interneurons in the deutocerebrum of Periplaneta and Apis using glass electrodes and stained intracellularly some of these interneurons. Periplaneta: Interneurons in the deutocerebrum could be classified into three groups on the basis of the stimulus-response relationships. 1. The activity of the first group increases with increases in relative humidity. 2. The activity of the second group increases with decreases in relative humidity. 3. The activity of the third group has a peak at intermediate relative humidity. These activities were recorded from interneurons which located in the restricted area (cetro-dorsal area in deutocerebrum); the activities of the first group were recorded dorsally in the area, those of the … More second were ventrally in the area, and those of the third were recorded in the vicinity of its central area. There were various kinds of interneurons time courses of activities of which were different each other; phasic-tonic, phasic, tonic, and inhibitory-excitatory (phasic and tonic) types etc. Apis: Interneurons could be classified into only two groups in the basis of the stimulus-response relationship, instead of 3 groups in Periplaneta. The activity of one group increases with increasing humidity and that of the other increases with decreasing humidity. There were many kinds of the interneurons the time courses of activites of which were similar to those in Periplaneta. Some interneurons could be stained intracellularly. These were classified morphologically into two types, local interneurons and projection interneurons. The local interneuron spreads its neurites within dorsal and ventral area of the deutocerebrum and has no axon. The projection neuron spreads its neurites within the restricted area (probably only one glomerulus) and has a long axon. Less