Heteronomous rhythmic activity of neurosecretory cells in the silkmoth

Abstract

Electrical action potentials of neurosecretory cells producing pheromone biosynthesis-activating neuropeptide (PBAN) and electrocardiograms were recorded from female pupae of Bombyx mori and the correlation between firing activity of the cells and cardiac activity was analyzed. PBAN producing cells localized in the suboesophageal ganglion (SOG) generated clusters of action potentials at an interval of 30–60 min. The firing activity rhythm at a middle pupal period was closely related to heartbeat reversal rhythm: an active phase of the cells was usually apparent during anterograde pulse phases. Electrocardiograms at a late pupal period often revealed brief oscillatory potentials (15–25 Hz in frequency) of unknown origin. The firing activity rhythm of PBAN cells closely correlated with the rhythmic appearance of clustered oscillatory potentials. Transection of connectives between the brain and SOG abolished rhythmic activity of the cells. These results suggest that a rhythmic firing activity of the PBAN cell system is heteronomously generated by a cerebral neuronal mechanism and the cerebral mechanism relates the cell system to other neuronal mechanisms controlling cardiac activity and oscillatory potential rhythms.