We studied by immunocytochemistry and Western blots the identity and cellular distribution of voltage-gated calcium channels within dopaminergic neurons of the rat retina. The aim was to associate particular calcium channel subtypes with known activities of the neuron (e.g., transmitter release from axon terminals). Five voltage-gated calcium channels were identified: alpha1A, alpha1B, alpha1E, alpha1F, and alpha1H. All of these, except the alpha1B subtype, were found within dopaminergic perikarya. The alpha1B channels were concentrated at axon terminal rings, together with alpha1A calcium channels. In contrast, alpha1H calcium channels were most abundant in the dendrites, and alpha1F calcium channels were restricted to the perikaryon. The alpha1E calcium channel was present at such a low density that its cellular distribution beyond the perikaryon could not be determined. Our findings are consistent with the available pharmacological data indicating that alpha1A and alpha1B calcium channels control the major fraction of dopamine release in the rat retina.
(c) 2006 Wiley-Liss, Inc.