IMMUNOCYTOCHEMICAL LOCALIZATION OF POLYAMINES IN THE TIGER SALAMANDERRETINA

The polyamines spermine and spermidine are present in neural tissue, b ut their functions there are not well understood. Recent work suggests that the NMDA subtype of glutamate receptors, other glutamate recepto r subtypes, and certain K+-channels, are neural targets for polyamines . To better understand the neuron-specific roles of polyamines, we hav e developed antibodies that interact with spermine and spermidine in a ldehyde-fixed tissue and used these antibodies in immunocytochemical s tudies to determine the cellular localization of these polyamines in t he tiger salamander retina. The affinity-purified, polyclonal antibodi es were highly specific for spermine and spermidine, exhibiting < 1% c ross reactivity with putrescine, and virtually no cross-reactivity wit h GABA, arginine, lysine, or glutaraldehyde. Polyamine labeling was mo st abundant in cells in the inner half of the inner nuclear layer and in the ganglion cell layer. Some cells in the outer half of the inner nuclear layer are labeled, and there was some labeling in both synapti c layers. Double-labeling experiments indicated (1) all GABAergic amac rine cells were polyamine-positive; and (2) all ganglion cells (identi fied by back-filling after microinjections of rhodamine in the optic n erve) were polyamine-positive. These results are consistent with a rol e for polyamines as modulators of NMDA receptor function and channel f unction in the inner retina.