Alterations of functional glucose use and ligand binding to second messenger systems following unilateral orbital enucleation

Quantitative autoradiography was used to examine the effect of lesioning a well-defined glutamatergic system (retinofugal fibres) on 3H]forskolin binding to Gs-adenylate cyclase and 3H]PDBu (phorbol-12,13-dibutyrate) binding to protein kinase C (PKC) in the rat visual system at 1, 5, 10 and 20 days after unilateral orbital enucleation. Local cerebral glucose utilisation was determined in the same animals using quantitative 14C]2-deoxyglucose autoradiography. At 5 days post-lesion, 3H]forskolin binding sites were significantly reduced in the visually-deprived superior colliculus (-14 +/- 1%) and dorsal lateral geniculate body (-8 +/- 2%), and these reductions persisted until 20 days post-lesion. There were no significant alterations in the amount of 3H]PDBu binding in any region in the visually-deprived hemisphere following enucleation. Function-related glucose use was significantly reduced throughout the visual pathway after enucleation. In this study, there was no conclusive evidence of plastic modifications of second messenger systems in the rat visual system despite a general depression of visual function following lesion of retinofugal fibres.