1988 Fiscal Year Final Research Report Summary

Neural mechanism of sexual excitation

Research Project

Project/Area Number	62540547
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	動物発生・生理学
Research Institution	Okayama University
Principal Investigator	SAKAI Masaki Okayama University Associate Professor, 理学部, 助教授 (30027502)
Co-Investigator(Kenkyū-buntansha)	YAMAGUCHI Tsuneo Okayama University Professor, 理学部, 教授 (60000816)
Project Period (FY)	1987 – 1988
Keywords	cricket / mating behavior / behavioral switching / motivation / key stimulus / chain reaction / ニューロン
Research Abstract	The present study was intended to understand neural basis of behavioral switching. The attitude of the male cricket toward the female changes from copulatory to evasive as soon as the copulation is completed. We found that this occurred when hair sensilla inside the dorsal cavity of the epiphallus were pressed with the copulatory papilla of the female during genitalia unification. Moreover, we succeeded in ending the mating period artificially by applying a similar pressure on that sensilla while the male was exhibiting an intense posture in response to the stimulation of the back. It is the first demonstration in insects. Then, we examined giant interneurons in the ventral nerve cords to see if they showed different responsiveness to a wind when it was applied to the cerci in different sexual excitation states. During copulatory mood. some of the giant neurons responded with a latency of 5-10 ms for 40 ms to the sound. After an evasive mood was induced by electrical stimulation of the genitalia the neural response was suppressed but recovered soon when a copulatory mood was induced by neck stimulaton. However. such a case was observed in only a small number of the preparations (15%). No case was found in which the neural response was in the reverse direction. In 85% of the males, the interneuron response was virtually the same in both behavioral states. More data are needed to establish a relationship between behavioral change and neural events.