cGMP-mediated effects on the physiology of bovine and human retinal Muller (glial) cells

1. Whole-cell currents of freshly dissociated or cultured Muller cells from human and bovine retinas were studied using the perforated-patch and standard whole-cell recording techniques. 2. We found that internal perfusion of cGMP or external exposure to 8-bromo-cGMP activated a calcium permeable, non-selective cation current in Muller cells, the principal glial cells of the retina. In addition, the activity of calcium-activated potassium channels increased markedly. These currents were minimally affected by cAMP. 3. Molecular studies using the reverse transcription-polymerase chain reaction demonstrated that human Muller cells in culture contain transcripts closely related to the rod cyclic nucleotide-gated (CNG) channel. 4. Since guanylate cyclase is a known target for nitric oxide (NO), we tested the effect of NO donors on Muller cell currents. These agents induced currents that were qualitatively similar to those activated by cGMP. 5. Our experiments support the idea that the NO-cGMP pathway regulates the physiology of Muller cells and may play a role in integrating neuron-glia interactions in the retina.