Physiological study on biological rhythm formation in multi-oscillatory cell system

家蚕的四对脑神经分泌细胞产生蚕丝素（一种胰岛素样肽），表现出节律性的放电活动。单个细胞的活动节律和细胞间的相互关联分析揭示了超放电节律的巨大变异性和细胞耦合的异质性。产蚕素细胞群的总放电活动表现出具有多频率成分的复杂节律性。根据细胞的总放电模式和血淋巴中蚕蛹素降解的时间过程，估计了血淋巴中蚕蛹素浓度的时间模式，并计算了功率谱。功率谱在较宽的频率范围内表现出典型的1/f波动特征，从而表明神经分泌细胞之间弱耦合产生了这种激素分泌的特征模式，这种时间模式似乎适合维持激素的生物作用。分离出脑- cc - ca复合物，置于生理盐水中，观察产蚕蚕素细胞的放电活性。在这种体外系统中也观察到类似的节律性放电活动，但在盐水浴中应用阿托品完全阻断了这种活动，因此神经分泌细胞的活动是由脑内胆碱能神经元调节的。产蚕素细胞系统的细胞组织和行为可能是理解脊椎动物和无脊椎动物弱耦合多振荡系统的一个简单模型。

Four pairs of cerebral neurosecretory cells producing bombyxin (an insulin-like peptide) in the silkmoth Bombyx mori show rhythmic firing activity. Analyses of activity rhythms of individual cells and cross-correlation between cells revealed a large variability in ultradian firing rhythms and heterogeneity in cellular coupling. A total firing activity of a population of bombyxin producing cells showed a complex rhythmicity with multiple frequency components. Based on the total firing patters of cells and time course of bombyxin degradation in the haemolymph, temporal patters of bombyxin concentration in the haemolymph were estimated and power spectra were calculated. Power spectra showed a typical 1/f characteristics of fluctuation in a broad range of frequency, thereby suggesting that neurosecretory cells coupled weakly with each other to generate such a characteristic patter of hormone secretion, a temporal pattern which seems suitable for maintaining biological actions of the hormone. Brain-CC-CA complex was isolated and placed in a physiological saline and firing activity of bombyxin producing cells was examined. Similar rhythmic firing activity was observed in such an in vitro system and it was completely blocked by application of atropine in the saline bath, hence the activity of neurosecretory cells is regulated by cholinergic neurons in the brain. Cellular organization and behavior of the bombyxin producing cell system may be a simple model for understanding weakly-coupled multi-oscillator systems in vertebrates and invertebrates.