Steven DeVries; Northwestern University
Biochemistry, Biophysics, and Structural Biology | Life Sciences | Molecular Biology
Cone photoreceptors are electrically coupled such that when the electrical potential in one cell changes, it also changes in adjacent, coupled cells. Phosphorylation of the cone gap junction protein, connexin 36 (Cx36), determines whether a coupling channel is “open” or “closed”. Cx36- containing gap junctions are phosphorylated in the open state and dephosphorylated in the closed state. Cone-cone gap junction modulation has not been extensively studied, however, the presence of rod-cone gap junction modulation raises the possibility that the same is true for cone pairs. Pieces of thirteen-lined ground squirrel retina were removed from the eye and the tissue was treated with either the neurotransmitter dopamine or a dopamine antagonist and then labeled with separate antibodies to Cx36 and phosphorylated Cx36. Cone-cone gap junctions were then imaged in the tissue slices and the colocalization of the antibody labels under the two conditions was quantified. We hypothesized that dopamine would also modulate electrical coupling between mammalian cone photoreceptors, which is also mediated by Cx36. Preliminary analysis suggests that the ratio of dephosphorylated to phosphorylated gap junctions is higher in dopamine versus the dopamine antagonist treated tissue. The results are consistent with the idea that dopamine, which is released during the daytime, induces dephosphorylation and thus closes gap junctions between cone cells in the ground squirrel, potentially reducing a source of “neural blur”*.
Li, X., & DeVries, S. (2011). Dopamine regulation of cone-cone gap junctions in ground squirrel retina. The Journal of Experimental Secondary Science, 1(2). Retrieved from http://digitalcommons.imsa.edu/student_pr/3/