The Analysis of Neuronal Mechanism of Vocal Nucleus related to Testosterone in Passerine.

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The purpose of this study is to clarify the physiological function and anatomical structure of the dorsomedial nucleus (DM) in the vocal control system and in the producing of sexually different acoustic strtuctures of distance calls (DC) of instinct behavior in sexually mature Bengalese finches (Lonchura striata var. domestica) Immature males and females have acoustically similar distance calls and in sexually mature male under the effect of testosterone, sex hormone, the acoustic structures of distance calls show sexual differences. This behavioral dichotomy is due to innervation of the neural input from RA to DM when robust nucleus of the arichistriatum (RA) in the male developed sexually mature. The above findings are results of analyzing acoustic structures of distance calls before and after electrolytic lesions of the bilateral RA in sexually mature males. After bilateral RA lesioning, these males have produced distance calls acoustically similar to those of female. We studied at … More the cellular level recording of the impulses of neurons in DM by microelectrode. The response patterns of spike discharges from neurons in DM of males and females did not show sexual difference. Mean impulse number of spike discharges increased just before vocalization of distance call.We investigated microstructure of the nervous system of DM in mature male by anatomical method. The synapse of anterograde labeling with neural tracers was observed to be excitable synapse. The characteristic structure of DM in male has axonal input of nerve connection from RA to the dorsoventral side in DM and this axonal input connected the neuronal circuit related to producing of distance calls.We investigated response patterns from the results of multi-unit recording of spike discharges from neuron in DM of mature males and females when we stimulated left and right acoustic organs by the method of playback of DC.The duration of the firing spike discharges producing distance call in male is longer than that in female. Also the number of impulse frequencies in male is higher than that in female.These results suggest that axonal input of neuronal connection from the RA to DM of sexually mature male modulates the acoustic structure of its DC.We clarified by neuroethological studies that the neural input from the RA to DM was due to action of testosterone, sex hormone. Less