Intra-vitreal injection of substance P antibodies as an antagonist in the vertebrate (fish) retina.

A method is described for using substance P (SP) antibodies as an antagonist in the retina of a cyprinid fish, the roach (Rutilus rutilus). Antibody solution (10 microliters) injected into the vitreous was found by immunohistochemical localization to penetrate the neural retina up to the level of the inner margin of the inner nuclear layer. Thus, the inner plexiform layer, where SP would normally be released, was well infiltrated. Similar penetration patterns were observed 2 or 24 h after injection. The physiological effectiveness of the antibody was demonstrated indirectly by measuring its effect upon the spatial coupling of the horizontal cells. Previous work suggested that SP stimulates dopamine release which normally uncouples the horizontal cell somata but not the syncytium of their axon terminals. In retinae isolated from antibody-injected eyes, the horizontal cell somata (but not axon terminals) were indeed found to be significantly more strongly coupled, consistent with the blockage of SP-induced, presumably tonic, release of dopamine. The results suggest that peptide antisera can be useful as pharmacological tools to investigate electrophysiological effects of neuropeptides in the retina as in other parts of the central nervous system.