Retinal benzodiazepine receptors are destroyed by kainic acid lesions

Alterations in retinal neurotransmitter receptors and neuropeptides of the chick by kainic acid and acrylamide

The effects of intraocular injection of kainic acid and acrylamide upon retinal neuropeptides and high affinity binding sites have been determined in the chick. Kainic acid causes a sharp reduction in Met-enkephalin and somatostatin while neurotensin levels are unchanged. This treatment also lowers the extent of cholinergic muscarinic but not of [3H]naloxone or [3H]spiroperidol binding. In contrast, acrylamide treatment causes major increases of retinal Met-enkephalin and neurotensin concentrations. The binding of [3H]naloxone is also increased, and no reductions of any peptide or binding intensity were observed. The results indicate the plasticity of retinal neuropeptide levels and the selectivity with which these can be modulated.

Dose-dependent effects of intravitreal kainic acid on specific cell types in chicken retina

In chicken retina, approximately two thirds of the bipolar cells and most amacrine cells are destroyed after intravitreal injection of from 20 to 60 nmoles of kainic acid. These cells, plus horizontal cells are destroyed after intravitreal injections of 120 nmoles of kainic acid. One third of the bipolar cells, Müller glial cells, photoreceptors and ganglion cells seem to be much more resistant. The resistance of the ganglion cells to intravitreal kainic acid is unusual and is not found in mammalian retinas. Dopaminergic amacrine cells may also be resistant to kainic acid. It is suggested that kainic acid interacts directly with bipolar cells and horizontal cells, depolarising the bipolar cells and horizontal cells and thereby killing them, while hyperpolarizing the ON-bipolar cells. The possibility that amacrine cell death may be an indirect result of kainic acid's effects on bipolar cells is discussed. Whatever the precise way in which kainic acid causes cell death, the technique of causing lesions is useful for defining the localization of retinal and particularly amacrine cell transmitter systems.