Retinal neurons that express the immediate early gene c-fos after light exposure were characterized by neurotransmitter content using histochemical and immunocytochemical staining. In Northern blots the amount of c-fos mRNA peaked at 30 min, but remained detectable 60 min following light stimulation. Fos proteins were seen in the inner nuclear and ganglion cell layers, and the staining was most intense two and three hours after beginning the light exposure. In the ganglion cell layer 30-40% of Fos-immunoreactive cells were cholinergic displaced amacrine cells and 3-5% were ganglion cells. In the inner nuclear layer 24% of Fos-immunoreactive cells were Type I and 7% Type II NADPH-diaphorase-reactive (nitric oxide synthase) amacrine cells, 11% were tyrosine hydroxylase-containing cells, and 10-15% cholinergic amacrine cells. No Fos immunoreactivity was seen in serotoninergic, somatostatin- or VIP-immunoreactive cells, bipolar, horizontal or photoreceptor cells. Nicotine, kainic acid, NMDA and SCH 38393, a dopamine D1 receptor agonist, induced Fos immunostaining in the inner nuclear and ganglion cell layers, but administration of the corresponding receptor blockers mecamylamine, kynuretic acid, MK-801, haloperidol and SCH 23990 did not prevent light-induced Fos expression.