[3H]-Dopamine release from the rabbit retina

Abstract

[³H]-Dopamine was found to be released from the rabbit retina in vitro by light stimulation, by 40 mM K +, and by α-MSH (α-Melanocyte-Stimulating Hormone) down to about 10⁻⁷ M. The effect of α-MSH was dose-dependent. A number of known and putative retinal neurotransmitters and agonists (GABA, muscimol, glutamic acid, kainic acid, glycine, and carbachol, all 10⁻⁴ M) were without significant effect. The results show that it is unlikely that there are excitatory receptors on the retinal dopaminergic neurons to any of the conventional transmitters. Further, α-MSH seems of interest as a possible neuroactive retinal substance, which has previously not been suspected.