Geusz M E, Page T L
Department of Biology, Vanderbilt University, Nashville, TN 37235.
J Comp Physiol A. 1990 Apr;166(6):795-801. doi: 10.1007/BF00187325.
The eye of the mollusk Bulla gouldiana contains a pacemaker that generates a circadian rhythm in compound action potentials (CAPs) in the optic nerve. In this paper, we present evidence of a second circadian rhythm in the optic nerve of the eye maintained in darkness at 15 degrees C. This is a rhythm in the frequency of small (10-40 microV) neural impulses that occurs about 12 h out-of-phase with the rhythm in CAPs. Typically, the small-spike frequency is at a minimum within an hour of the peak in CAP frequency and is maximal during the subjective night. Like the CAP rhythm, the phase of the small-spike rhythm is determined by the prior light/dark cycle. A rebound in small-spike activity following the end of a light pulse and the presence of photoinhibited impulses in surgically reduced eyes suggests that the cells that generate the small-spikes may be photoreceptors that are inhibited by light. In addition, by using isolated nervous system preparations, we have found that small-spikes occur in the two optic nerves in a one-for-one relationship immediately following a light-to-dark transition. This inter-eye communication may be involved in the coupling of the ocular pacemakers.
海兔（Bulla gouldiana）的眼睛含有一个起搏器，它能在视神经的复合动作电位（CAPs）中产生昼夜节律。在本文中，我们展示了在15摄氏度黑暗环境中保存的眼睛视神经中存在第二种昼夜节律的证据。这是一种小幅度（10 - 40微伏）神经冲动频率的节律，其与CAPs节律的相位相差约12小时。通常，小尖峰频率在CAP频率峰值的一小时内处于最低水平，在主观夜间达到最高。与CAP节律一样，小尖峰节律的相位由先前的明暗周期决定。光脉冲结束后小尖峰活动的反弹以及手术切除眼睛中存在光抑制冲动表明，产生小尖峰的细胞可能是受光抑制的光感受器。此外，通过使用分离的神经系统制剂，我们发现，在从光照到黑暗转变后，两条视神经中会立即以一对一的关系出现小尖峰。这种眼间通信可能参与了眼部起搏器的耦合。
