期刊
VISUAL NEUROSCIENCE
卷 21, 期 5, 页码 791-805出版社
CAMBRIDGE UNIV PRESS
DOI: 10.1017/S0952523804215127
关键词
electrical coupling; gap junction; retina
资金
- NEI NIH HHS [EY10608, EY10121, R01 EY010121, P30 EY010608] Funding Source: Medline
Gap junctions are commonplace in retina. often between cells of the same morphological type, but sometimes linking different cell types. The strength of coupling between cells derives from the properties of the connexins, but also is regulated by the intracellular environment of each cell. We measured the relative coupling of two different gap junctions made by AII amacrine cells of the rabbit retina. Permeability to the tracer Neurobiotin was measured at different concentrations of the neuromodulators dopamine, nitric oxide, or cyclic adenosine monophosphate (cAMP) analogs. Diffusion coefficients were calculated separately for the gap junctions between pairs of AII amacrine cells and for those connecting AII amacrine cells with ON cone bipolar cells. Increased dopamine caused diffusion rates to decline more rapidly across the AII-AII gap junctions than across the AII-bipolar cell gap junctions. The rate of decline at these sites was well fit by a model proposing that dopamine modulates two independent gates in AII-AII channels. but only a single Late on the AII side of the AII-bipolar channel. However. a membrane-permeant cAMP agonist modulated both types of channel equAIIy. Therefore. the major regulator of channel closure in this network is the local cAMP concentration within each cell. as regulated by dopamine. rather than different cAMP sensitivity of their respective gates. In contrast, nitric oxide preferentiAIIy reduced AII-bipolar cell permeabilities. Coupling from AII amacrine cells to the different bipolar cell subtypes was differentiAIIy affected by dopamine. indicating that light adaptation acting via dopamine release alters network coupling properties in multiple ways.
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