McMahon D G, Mattson M P
Department of Physiology, University of Kentucky, Lexington 40536-0084, USA.
Brain Res. 1996 Apr 29;718(1-2):89-96. doi: 10.1016/0006-8993(96)00043-1.
Electrical synapses, and their structural manifestation, gap junctions, are critical elements of retinal circuitry. These synapses are subject to both rapid modulation and slower structural changes by physiological signals which mediate changes in the adaptational state of the retina. The electrical synapses of fish retinal horizontal cells are an excellent preparation for in vitro studies of electrical synapses. We have examined the rapid modulation of electrical coupling by dopamine and effects on the expression and maintenance of electrical synapses by cell calcium in pairs of horizontal cells isolated from retinas of the giant danio (Danio aquipinnatus). We report that rapid modulation by dopamine reduces junctional conductance by modifying gap junction channel gating, while maintaining cells in reduced calcium medium, and lowering intracellular calcium concentration, results in the loss of electrical coupling. The effects of calcium on synaptic maintenance may be related to structural changes observed in horizontal cell electrical synapses during light adaptation.
电突触及其结构表现形式——缝隙连接，是视网膜神经回路的关键组成部分。这些突触会受到生理信号的快速调节以及较慢的结构变化影响，而这些生理信号介导了视网膜适应状态的改变。鱼类视网膜水平细胞的电突触是体外研究电突触的绝佳样本。我们研究了多巴胺对电耦合的快速调节作用，以及细胞内钙对从巨暹罗鲤（Danio aquipinnatus）视网膜分离出的成对水平细胞中电突触表达和维持的影响。我们报告称，多巴胺的快速调节通过改变缝隙连接通道的门控来降低连接电导，而将细胞维持在低钙培养基中并降低细胞内钙浓度会导致电耦合丧失。钙对突触维持的影响可能与光适应期间水平细胞电突触中观察到的结构变化有关。
