Co-ordination of firing activity of neurosecretory cells with cardiac activity in the silkmoth Bombyx mori.
Electrocardiograms and electrical action potentials of cerebral neurosecretory cells producing bombyxin (an insulin-related neuropeptide) were simultaneously recorded from male pupae of the silkmoth Bombyx mori. A pupa showed alternations in the flow of haemolymph due to a rhythmic heartbeat reversal: a train of retrograde heartbeat with a slow pulse rate followed a train of anterograde heartbeat with a higher pulse rate. Intervals of heartbeat reversals changed throughout the pupal period. At any stage of the pupal period, firing activity of a population of bombyxin-producing (BP) cells rapidly declined after the start of anterograde heartbeat and an inactive state of cells continued during an anterograde heartbeat period. Analyses of ultradian bursting rhythmicity of a single BP cell revealed that a bursting phase of the cell often delayed at a time when the anterograde cardiac activity occurred at the preceding inter-burst period of firing rhythm. The results support the postulation that firing (secretory) activity of an insect neurosecretory cell system may be co-ordinated with circulation of haemolymph for rapid and pulsatile delivery of the peptides released to target organs.
Ichikawa
Toshio
T
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan. tichiscb@mbox.nc.kyushu-u.ac.jp
Okada
Yoshihiro
Y
D000200:Action Potentials; D000818:Animals; D012831:Bombyx / Q000254:growth & development / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D008297:Male; D009490:Neurosecretory Systems / Q000502:physiology*