Effects of intravitreal and intravenous administrations of dopamine on the standing potential and the light peak in the intact chicken eye.

We studied the modifications of the standing potential (SP) of the eye and of the light peak (LP) after exposure to dopamine, a neurotransmitter released at light by the inner retina and known to affect electrical properties of the retinal pigment epithelium. Intravenous or intravitreal injections of dopamine (DA) were performed on intact chickens. "Choroidal" application (through an intravenous injection) induced a transient increase of the SP and the LP was preserved. On the other hand, "apical" applications of DA (through an intraocular injection) also increased the SP but considerably depressed the LP. These results are in agreement with the hypothesis that the light-induced release of dopamine from the neuroretina may be responsible for the LP generation in the intact chicken eye.