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Michael L. Risner, Douglas McMahon; The Influence Of Dopamine On The Response Dynamics Of Dopaminergic Amacrine Cells. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4323.
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© ARVO (1962-2015); The Authors (2016-present)
Dopamine plays an integral role in modulating retinal circuitry during light adaptation. In the retina dopamine is synthesized and released by a small number dopamingergic amacrine (DA) cells. Previous studies examining the light-driven electrical response profiles of DA cells found three types of responses: sustained responses, transient responses, and light-independent responses. In the present study we recorded the light-driven responses from DA cells in retinas that are depleted of dopamine.
DA cells were targeted for recording using a transgenic mouse expressing red fluorescent protein (RFP) under the control of the tyrosine hydroxylase (TH) promoter (TH::RFP). To examine the role of dopamine specifically within the retina, we generated mice with a conditional allele of TH using the Cre/loxP recombination system and crossed TH::RFP/CHX10-Cre mice, which specifically express Cre recombinase in the retina, producing TH::RFP+/CHX10+/-/THloxP/loxP (TH::RFP/rTHKO) mice. Retinas were quickly dissected from the eye in Ames medium under dim red light and whole mounted in a recording chamber with continuous Ames medium exchange heated to 36 deg C. Light-driven responses were evoked using a 525 nm LED presented for 3 s.
Preliminary results suggest DA cells from rTHKO retinas produce spontaneous activity and light-driven responses comparable to DA cells from retinas that have usual dopamine levels.
These results indicate that dopamine does not affect the spontaneous activity or gross light-driven responses of DA cells. It may be the case that even low amounts of dopamine found in the rTHKO mice is sufficient to drive the basic responses of DA cells, and the retina requires additional challenge to reveal the influence of dopamine on the response dynamics of DA cells.
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