Response linearity and kinetics of the cat retina: The bipolar cell component of the dark-adapted electroretinogram

Abstract

The electroretinogram (ERG) of the dark-adapted cat eye in response to brief ganzfeld flashes of a wide range of intensities was recorded after intravitreal injection of n-methyl dl aspartate (NMdlA, cumulative intravitreal concentration of 1.3–3.9 mM) to suppress inner-retinal components, and after intravitreal dl or L-2-amino-4-phosphonobutyric acid (dl-APB, 1–3 mM; l-APB, 1.2 mM) and 6-cyano-7-nitroquinoxaline-2, 3 dione (CNQX, 40–60 µM), to suppress all post-receptoral neuronal responses. Rod PII, the ERG component arising from rod bipolar cells, was derived by subtracting records obtained after APB and CNQX from post-NMDLA records. When we measured the derived response at fixed times after the stimulus, we found that PII initially increased in proportion to stimulus intensity without any sign of a threshold. The leading edge of PII at early times after the stimulus, when the response was still small, was well described by V(t) = kI(t −td)5 where k is a constant, I is the intensity of the stimulus, and td is a brief delay of about 3 ms. Correspondingly, the time for the response to rise to an arbitrary small criterion voltage Vcrit was adequately fitted by tcrit = td + (Vcrit/kI)1/5. The time course of the leading edge of the PII response can be interpreted to indicate that the mechanism generating PII introduces three stages of temporal integration in addition to the three stages that are provided by the mechanism of the rod photoreceptors. This finding is consistent with the operation within the rod bipolar cell of a G-protein cascade similar to that in the rods.

Postreceptoral contributions to the light-adapted ERG of mice lacking b-waves

“…tetrodotoxin to block sodium-dependent spiking activity, and n-methyl D-aspartate (NMDA) (e.g. Robson and Frishman, 1995) or GABA (Robson et al, 2004) to minimize inner retinal contributions to the ERG, indicate that the positive intrusion originates at least in part from neurons proximal to Off bipolar cells (unpublished observations). Additional experiments would be needed to further specify the third order contributions to the response.…”

Dopaminergic modulation of tracer coupling in a ganglion-amacrine cell network

“…The light source was an array of green light-emitting diodes (LEDs: peak output 560 nm) enclosed in a metal tube, 50 mm in length with a white matte surface (Robson & Frishman, 1995). The LEDs illuminated a white concave diffusing screen 35 mm in diameter at the other end of the metal tube.…”

Thenob2mouse, a null mutation inCacna1f: Anatomical and functional abnormalities in the outer retina and their consequences on ganglion cell visual responses

“…This can be evaluated noninvasively with the electroretinogram (ERG). When only synaptic transmission is compromised, the a-wave component, reflecting activity of rod and cone photoreceptors (Lamb, 1996), is spared, while the b-wave, reflecting predominantly rod or cone depolarizing bipolar cell (DBC) activity (Robson & Frishman, 1995, 1998Kofuji et al, 2000;Sharma et al, 2005), is reduced. This "negative" ERG pattern has now been reported in mice with mutations in genes encoding mGluR6 (Masu et al, 1995), nyctalopin (Pardue et al, 1998), the G-protein subunit Gα O1 (Dhingra et al, 2000(Dhingra et al, , 2002, the β 2 subunit of VDCCs (Ball et al, 2002), the presynaptic cytomatrix protein bassoon (Dick et al, 2003), or calcium-binding protein 4 (Haeseleer et al, 2004).…”