Spontaneous Electrical Activity in the Nervous System and its Modification by Biogenic Amines in the Silkworm Bombyx Mori (L)

Abstract

The present study was carried out to examine the effects of biogenic amines on the spontaneous electrical activity of the nervous system in the silkworm Bombyx mori. The activity recorded from different segments of the ventral nerve cord differed in the frequency and number of spike categories firing. The activity was highest between the subesophageal ganglion and 1st thoracic ganglion. Lower activity was recorded in the thoracic part of the cord and the activity increased in the abdominal cord. More or less the same level of activity was recorded from all the abdominal segments of the cord. The above trend was the same from the 1st day to the 7th day of the 5th instar of the silkworm. However, the overall level of activity increased from the 1st day to the 7th day in tune with the increasing complexity of the peripheral nervous system in the silkworm as the 5th instar progressed. Treatment of the cord with solutions of putative neurotransmitter substances, viz. epinephrine (EP), norepinephrine (NEP), dopamine (DA) and 5-hydroxytryptamine (5-HT) at different concentrations from 1x10-8 M to 1x10-4 M showed elevation at lower concentrations and
decrease at 1x10-4 M. The concentration at which maximum elevation could be elicited varied between the above transmitters. Biochemical analyses revealed the presence of these biogenic amines in the silkworm nervous system. Thus the possibility remains that one or more of these substances could act as neurotransmitters in the silkworm nervous system.

Keywords: Silkworm; 5th Instar; Spontaneous electrical activity;
Biogenic amines; Neurotransmitters.