Block G D, Roberts M H, Lusska A E
Department of Biology, University of Virginia, Charlottesville 22901.
J Biol Rhythms. 1986 Fall;1(3):199-217. doi: 10.1177/074873048600100303.
The eyes of Bulla gouldiana, a marine snail, contain circadian oscillators that are coupled to each other. Obvious candidates for the coupling signals are the optic nerve compound action potentials (CAPs) that express the circadian rhythm and lead to efferent impulses in the contralateral optic nerve. In the present experiments, the role of the CAPs as coupling signals was evaluated. We found that, following desynchronization of the two ocular oscillators by phase-delaying one eye with manganese, subsequent phase shifts in the initially unshifted ocular rhythm only occurred during the time that efferent optic nerve signals were present. In addition, in the absence of ocular desynchrony, phase shifts of the ocular rhythm could still be effected by activation of the efferent pathway. The influence of efferent impulses on identified retinal cells was also evaluated. No effect of efferent signals on receptor layer cells was detected, while it was found that efferent impulses generated depolarizations in basal retinal neurons (BRNs), the putative circadian oscillator cells. Depolarization of the BRNs has been shown previously to be involved in the light entrainment pathway. Depolarization appears to be similarly involved in the coupling pathway, since membrane depolarizations that mimicked the efferent-induced postsynaptic potentials likewise generated phase shifts of the ocular rhythm.
海蜗牛（Bulla gouldiana）的眼睛含有相互耦合的昼夜节律振荡器。耦合信号的明显候选者是表达昼夜节律并导致对侧视神经传出冲动的视神经复合动作电位（CAPs）。在本实验中，评估了CAPs作为耦合信号的作用。我们发现，在用锰使一只眼睛相位延迟从而使两个眼振荡器去同步后，最初未移位的眼节律随后的相位偏移仅在存在传出视神经信号的时间内发生。此外，在没有眼去同步的情况下，眼节律的相位偏移仍可通过激活传出通路来实现。还评估了传出冲动对已识别视网膜细胞的影响。未检测到传出信号对受体层细胞的影响，而发现传出冲动在基底视网膜神经元（BRNs）（假定的昼夜节律振荡器细胞）中产生去极化。先前已表明BRNs的去极化参与光同步化途径。去极化似乎同样参与耦合途径，因为模拟传出诱导的突触后电位的膜去极化同样产生了眼节律的相位偏移。
