Purchase this article with an account.
Konstantin Gavrikov, Ye Long, Christianne E. Strang, Kent T. Keyser; Post Stimulus Excitation In Rabbit Retina. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4580.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
A subset of transient ON-OFF ganglion cells located in the inferior temporal part of the rabbit retina (approximately 2-5 mm below the visual streak) exhibit long lasting inward currents after the offset of light stimuli. This sustained excitation can be sufficient to cause action potentials. We used cholinergic and GABAergic receptor blockade to determine the involvement of excitatory and inhibitory systems on the observed post stimulus excitation (PSE) in different physiological conditions.
Dark adapted rabbit eyecups were used for whole cell and cell attached patch clamp recordings to test nature of post stimulus excitatory current. Whole cell configuration was obtained under visual infrared control. After recording, cell morphology was confirmed with injection of Lucifer Yellow. Under -50-60 mV holding potentials, 1s spot stimuli ranging from 50-400 um in diameter were applied before and during pharmacological blockade. A combination of 100 nM MLA, 100 uM hexamethonium bromide (Hex), 3 uM atropine and 20 uM TPMPA,10 uM SR 95531 was used to block cholinergic and GABAergic receptor activity, respectively. To test the influence of light/dark adaptation on the PSE a background stimulus of 10% of the spot intensity was applied.
Light stimuli that ranged from 50 to 400 um in diameter proportionally prolonged PSE, and in some cases caused action potentials up to 1-1.5 s after the offset of light stimuli. Bath application of MLA/Hex reduced the On/Off light responses and completely blocked or even reversed the inward post stimulus currents. In contrast, TPMPA/SR95531 greatly increased light induced responses and the PSE. Atropine modulated On/Off responses and slightly increased or had no effect on PSE. Short 5 min light adaptation with the 10% background stimulus reduced duration of PSE.
Pharmacological modulation of cholinergic excitatory and GABAergic inhibitory systems shows that the size of the PSE is determined by these systems. The excitatory PSE was mostly due to alpha-7, or alpha 6-containing nicotinic AChR activation with only a limited contribution from muscarinic AChRs. The currents were also modulated by GABA-A,C receptor activities. Light adaptation modulated the PSE. Thus nicotinic AChR activation may play role in light/dark adaptation and the modulation of the spatial organization of complex receptive fields. In contrast muscarinic AChR activation mostly affected the direct light-induced responses and might be involved in temporal modulation of the responses of ganglion cells with complex receptive fields.
This PDF is available to Subscribers Only