Purchase this article with an account.
Wesley Maddox, Emily McMains, Evanna Gleason; Nitric Oxide Regulates Neurotransmitter Release Onto Retinal Amacrine Cells. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4319.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Nitric oxide (NO) is synthesized in multiple cell types in the vertebrate retina including subsets of retinal amacrine cells. Nitric oxide synthase (NOS) has been localized to amacrine cell synaptic terminals presynaptic to other amacrine cells (Cao and Eldred, 2001) suggesting that NO is targeted to amacrine cell synapses. Here, we test the hypothesis that NO can regulate synaptic transmission between GABAergic amacrine cells.
Cultured GABAergic amacrine cells were derived from White Leghorn chick embryos (Gleason et al. 1993). Retinal slices were prepared from 3-7 week old chickens (Lindstrom et al. 2010). Chickens were sacrificed by IP injection of sodium pentobarbital (250 mg/kg) as approved by the LSU IACUC (#A3612-01). To examine the effects of exogenous NO, Amacrine cells in contact with other amacrine cells were recorded in whole-cell voltage clamp and exposed to the NO donor S-Nitroso-N-acetyl-DL-penicillamine SNAP (500µM). To examine the effects of endogenous NO, recordings were made from amacrine cells in light-adapted retinal slices.
SNAP produced a 3.7 (±1.4, n=4)-fold increase in the frequency of post synaptic currents (PSCs) recorded in amacrine cells. This response was consistent with an effect of NO on the unclamped presynaptic amacrine cells. When the NO scavenger 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (CPTIO, 10µM) is co-applied with SNAP, no increase in PSC frequency is observed (p=0.7, n=3). In the absence of Ca2+out, SNAP did not increase PSC frequency suggesting that the NO-dependent increase is Ca2+-dependent (p=0.4, n=8). For amacrine cells in slices, endogenous NO was manipulated with arginine (1mM), the substrate for nitric oxide synthase (NOS) or L-NAME (200µM) a NOS inhibitor. Cells were held at -85mV and incoming PSCs recorded. Arginine increased PSC frequency in 43% of cells and decreased PSC frequency in 57% of cells (n=7). L-NAME had diverse effects as well with 50% increasing PSC frequency and 50% decreasing frequency (n=8). Reversibility was demonstrated for arginine (2/3 cells) and L-NAME (4/5 cells) where wash data was obtained.
These results demonstrate that NO regulates synapses presynaptic to amacrine cells. The diverse effects of NO in retinal slices suggest that upstream sites of action can alter the synaptic outcome for a particular amacrine cell.
This PDF is available to Subscribers Only