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.