Physiological study of synchronous firing activity in insect neurosecretory cell systems

在家蚕的大脑中，有四对神经分泌细胞产生蚕素，一种与胰岛素相关的肽。鉴定了产虫素细胞的电信号，分析了产虫素细胞在蛹期的短期和长期活动模式。细胞的活动模式以动作电位的周期性放电为特征。电活动的周期与温度有关，在26℃时周期的平均±标准差为34.7±4.8 min。大脑半球的四个细胞在功能上是异质的：单个细胞具有特定的活动幅度和节律，从而表明细胞的超活动节律源于其内在的起搏器活动。脑电活动没有明显的昼夜振荡。日活动模式在蛹期早期（第2天或第3天）达到最大值。研究了四对具有超昼夜爆破节律的产蚕蛹素细胞之间的放电相关性。对同时活跃的细胞对之间的峰值活动进行交叉相关分析，通常揭示出放电的显著相关性：一个细胞的20-50%的峰值在另一个细胞的峰值放电之前或之后0.2秒内放电。神经分泌细胞之间的相互兴奋性交流使这组细胞成为一个弱耦合的多振荡器系统，它可能产生一种脉冲式的激素释放模式，这似乎是一种维持激素作用的有效的时间模式。

There are four pairs of neurosecretory cells producing bombyxin, an insulin-related peptide, in the brain of Bombyx mori. Electrical signals of the bombyxin-producing cells were identified and short-and long-term activity patterns of the cells throughout the pupal period were analyzed. Activity pattern of the cells was characterized by periodic discharges of a volley of action potentials. Periodicity of the electrical activity depended on the temperature and mean±SD of periods was 34.7±4.8 min at 26℃. Four cells in a brain hemisphere were functionally heterogeneous : individual cells had specific activity amplitudes and rhythms, thereby suggesting that an ultradian activity rhythm of a cell originates from its intrinsic pacemaker activity. There was no significant diel (circadian) oscillation in the electrical activity. Daily activity patterns had a maximum at an early stage (day-2 or 3) of pupal period. Firing correlations were examined among four pairs of bombyxin-producing cells with an ultradian bursting rhythm. Cross-correlation analyses of spiking activities between pairs of simultaneously active cells usually revealed a significant correlation of firings : 20-50% of spikes of a cell fired within 0.2 s before or after the other cell's spikes fired. The mutual, excitatory communication among neurosecretory cells make the set of cells a weakly coupled multi-oscillator system that may generates a pulsatile release pattern of their hormone that seems to be an efficient temporal pattern for maintaining hormonal actions.