apologies if posted before....

Neuron. 2011 Oct 6;72(1):101-10. doi: 10.1016/j.neuron.2011.07.030.

Rod vision is controlled by dopamine-dependent sensitization of rod bipolar cells by GABA.
Herrmann R1, Heflin SJ, Hammond T, Lee B, Wang J, Gainetdinov RR, Caron MG, Eggers ED, Frishman LJ, McCall MA, Arshavsky VY.

Abstract

Dark and light adaptation of retinal neurons allow our vision to operate over an enormous light intensity range. Here we report a mechanism that controls the light sensitivity and operational range of rod-driven bipolar cells that mediate dim-light vision. Our data indicate that the light responses of these cells are enhanced by sustained chloride currents via GABA(C) receptor channels. This sensitizing GABAergic input is controlled by dopamine D1 receptors, with horizontal cells serving as a plausible source of GABA release. Our findings expand the role of dopamine in vision from its well-established function of suppressing rod-driven signals in bright light to enhancing the same signals under dim illumination. They further reveal a role for GABA in sensitizing the circuitry for dim-light vision, thereby complementing GABA's traditional role in providing dynamic feedforward and feedback inhibition in the retina.
Our results demonstrate that the sensitivity and operational range of rod-driven vision are increased by dopamine-dependent GABAergic inputs onto rod DBCs. These findings expand the function of dopamine in the retina from its traditional role of establishing cone-vision dominance in daytime to acting as an enhancer of rod-driven circuitry. A previous study in zebrafish indicated that dopamine is required for the transmission of rod signals downstream from DBCs (Li and Dowling, 2000). We now show that dopamine increases the sensitivity of rod-driven responses at the level of DBCs. Together, these results indicate that dopamine regulates the entire primary rod pathway of mammalian vision. The fact that the desensitizing effect of the D1R knockout is observed in both dark-adapted mice and mice exposed to dim background light is consistent with significant levels of total dopamine (Nir et al., 2000) and dopamine release (Mills et al., 2007) even in dark-adapted retinas.

Copyright © 2011 Elsevier Inc. All rights reserved.

(Chavez AE, Grimes WN, Diamond JS. Mechanisms underlying lateral GABAergic feedback onto rod bipolar cells in rat retina. J Neurosci. 2010;30:2330–2339)
(Dunn FA, Doan T, Sampath AP, Rieke F. Controlling the gain of rod-mediated signals in the Mammalian retina. J Neurosci. 2006;26:3959–3970)

et al et al......

my eyesight has gone completely to crap! from okay to trifocals in 4 years....so I studied this stuff and looky what I found....(lots of other sources as well)

peace

BP