Omura Y, Ali M A
Cell Tissue Res. 1980;208(1):111-22. doi: 10.1007/BF00234177.
Electron microscopy of the pineal receptor cells in light- and dark-adapted brook trout, Salvelinus fontinalis and the rainbow trout, Salmo gairdneri, revealed no significant differences in the tubular and filamentous elements of the inner segment, neck and supranuclear regions. However, changes in synaptic relations between the photoreceptor and nerve cell were induced by light and darkness. In the light-adapted state, the synaptic relationship between axon terminals and photoreceptor basal processes predominates, while in darkness the synapses between photoreceptor basal processes and ganglion cell dendrites are more prominent. Further, in darkness, the photoreceptor basal processes show a number of synaptic vesicles and synaptic ribbons. These findings suggest that the sensory function of the fish pineal is enhanced during darkness but inhibited by light, and that the synaptic relationships are involved in the control of sensory activity in the pineal photoreceptor and ganglion cells. These results corroborate those of electrophysiological studies in that the maximal spontaneous discharge frequency of the ganglion cells occurs in the dark, and it also shows a burst when light is removed. The "typical" chemical synapse between the axon terminal and the photoreceptor basal process in light seems to function as an inhibitor.
对适应光照和黑暗环境的溪红点鲑（Salvelinus fontinalis）和虹鳟（Salmo gairdneri）松果体受体细胞进行电子显微镜观察发现，内段、颈部和核上区域的管状和丝状成分没有显著差异。然而，光照和黑暗会引起光感受器与神经细胞之间突触关系的变化。在适应光照的状态下，轴突终末与光感受器基部突起之间的突触关系占主导，而在黑暗中，光感受器基部突起与神经节细胞树突之间的突触更为突出。此外，在黑暗中，光感受器基部突起显示出许多突触小泡和突触带。这些发现表明，鱼类松果体的感觉功能在黑暗中增强但受光照抑制，并且突触关系参与了松果体光感受器和神经节细胞感觉活动的控制。这些结果证实了电生理研究的结果，即神经节细胞的最大自发放电频率出现在黑暗中，并且在去除光照时也会出现爆发。光照下轴突终末与光感受器基部突起之间的“典型”化学突触似乎起到抑制剂的作用。
