Modification of Spontaneous Electrical Activity by Neural and Blood-Borne Factors in the Silkworm Bombyx mori L.

Abstract

The objective of the present study was to examine the variations in the levels of spontaneous electrical activity during the 5 th instar development of the silkworm Bombyx mori and the possible mode of its regulation. The spontaneous electrical activity of the ventral nerve cord (VNC) showed an increase from the 2 nd day to the 7 th day of the 5 th instar. Treatment of the VNC with extracts of the central nervous system (CNS) from the 2 nd day larvae or hemolymph from the 7 th day larvae elevated the spontaneous electrical activity of the VNC in both the 2 nd and 7 th day larvae, while extracts from the 7 th day larvae or hemolymph from the 2 nd day larvae did not cause any perceptible effect. Acetylcholine (ACh, 10 -7 M) elevated the activity in both the 2 nd and 7 th day larvae. It is suggested that synthesis and release of neuromodulators from the CNS into the hemolymph could modify the activity of the nervous system at different stages of the life cycle and consequently the behavior in the silkworm.