Pharmacologically defined components of the normal porcine multifocal ERG

Abstract

Multifocal electroretinograms (mfERG) from isoflurane anesthetized pigs were recorded and sequential application of TTX, NMDA, APB and PDA were used to identify contributions to the mfERG from inner retinal neurons, ON-pathway, OFF-pathway and photoreceptors. The cellular origins of the first-order kernel (K1) and the first slice of the second-order kernel (K2.1) porcine mfERG are contributed from both inner and outer retina. For the K1 waveform, the n1 involved responses of cone photoreceptors and OFF-bipolar cells. The leading edge of p1 is dominated by ON-bipolar cell depolarization. The rear edge of p1, n2 and p2 are dominated by ON-bipolar activities and shaped by the activities of OFF-bipolar cells and retinal cells with NMDAr and voltage-gated sodium channels other than ganglion cells. The p3 is mainly inner retinal activities. For the K2.1 waveform, the p1 and n1 are the summation of activities of ON-, OFF-bipolar cells and retinal cells rich in NMDAr and voltage-gated sodium channels other than ganglion cells. The p2 seems to be related to the ganglion cells. Better understanding of the cellular origins of the normal porcine mfERG will be useful for comparing and defining the functional changes that may occur in diseased retinas.

The characteristics of multifocal electroretinogram in isolated perfused porcine eye

“…Assuming that the minimum vitreous concentration of ISO approximates its clinical MBC, 25 ll ISO in intra-vitreal injection would be double the minimum amount of ISO required. The concentrations of pharmacological agents, besides ISO and propofol, were evidently sufficient in previous experiments in other animals [18,19] and in pig [3,4,20] In our experiments, all these effects on the flash ERG were verified. NMDA is an ionotropic glutamateric receptor agonist that depolarizes cells with NMDA receptors (NMDAr), such as ganglion cells and amacrine cells.…”

“…Multifocal electroretinogram (mfERG) recordings obtained from anesthetized primates [1,2] and pig [3,4] have been measured before and after the injection of pharmacological agents with known effects in blocking the activities of specific neural circuits. These findings have been used to define the contributions of specific in vivo retinal pathways to the mfERG response.…”

Toxicity profiles of subretinal indocyanine green, Brilliant Blue G, and triamcinolone acetonide: a comparative study

“…P1 is of photoreceptor and bipolar cell origin [55,56] and is a good representative of outer retinal function. For ICG, the N1 amplitude was significantly smaller in injected eyes than in healthy fellow eyes (p00.023), and for BBG this was the case for N2 (p00.008), but the significance of these findings is unclear; N1 is probably of photoreceptor origin, and N2 is of unknown origin [55].…”

Pharmacological dissection of multifocal electroretinograms of rabbits with Pro347Leu rhodopsin mutation

“…The results showed that the middle and inner retinal activity contributed signifi cantly to the shaping of the mfERGs in rabbits, as in other animals such as monkeys, pigs, and cats. 11,24,25 Responses from the visual streak were successfully identifi ed by their higher amplitudes as reported, 20 After elimination of the neural activity of the middle retinal neurons by an intravitreal injection of APB and PDA, the cone responses were obtained. We found that the amplitude of the negative defl ection of the WT rabbits did not differ signifi cantly from that of the Tg rabbits, whereas Kondo et al 6 showed that the full-fi eld cone a-wave amplitudes elicited by strong stimuli were signifi cantly smaller in Tg than WT rabbits at 12 weeks of age.…”