Non-melanopsin-expressing SCN-projecting ganglion cells in the golden hamster retina

Abstract

Retinal ganglion cells (RGCs) expressing melanopsin have been described in different species. There is evidence that not all suprachiasmatic nucleus (SCN) projecting RGCs express melanopsin. The golden hamster was investigated to determine morphological characteristics of non-melanopsin expressing RGCs projecting to SCN. SCN-projecting RGCs were retrogradely labeled with fluorescent microspheres (Molecular Probes) and intracellularly injected with Lucifer yellow (Sigma-Aldrich). Melanopsin expressing RGCs were labeled with antiserum UF007 (a generous gift from Dr. Ignacio Provencio) that was generated in rabbit against mouse melanopsin peptide. Our preliminary data show that approximately 15% of intracellularly injected SCN-projecting RGCs did not express melanopsin. Those non-melanopsin expressing RGCs distributed across retina. Some of them had displaced somas in the inner nuclear layer. All of them exhibited large but sparse dendritic field. Most RGCs had 2-4 primary dendrites. Each primary dendrite branched for 3-5 times. Both uni- and bi-stratified ramification patterns were observed, suggesting both ON and OFF sublaminae provide inputs to non-melanopsin expressing RGCs in the golden hamster. Supported by The University of Hong Kong, The research grant council of Hong Kong (K.-F. So)