ABSTRACT
Given the important role of retinoids and thyroid hormone for optimal brain functioning and the tenuous relationship between retinoic acid (RA) and triiodothyronine (T3) signalings, we compared the effects of RA or T3 administrations on RA and T3 nuclear receptors (RAR, RXR and TR) and on their target genes, neuromodulin (GAP43) and neurogranin (RC3) in 24-month-old rats. Quantitative real time PCR and western blot analysis allowed us to verify that retinoid and thyroid signalings and GAP43 and RC3 expression are affected by age. By in situ hybridization we observed a decreased expression of RC3 in hippocampus, striatum and cerebral cortex. RARbeta, RXRbeta/gamma and GAP43 were up-regulated by RA as well as T3 treatment. The abundance of TRalpha/beta mRNA and RC3 expression were only increased by T3 administration in the whole brain. This up-regulator effect of T3 on RC3 was only observed in the striatum. During aging, T3 become a limiting factor alone able to correct the age-related concomitant hypo-activation of retinoid and thyroid signalings and alterations of synaptic plasticity.
Subject(s)
Aging/physiology , Calmodulin-Binding Proteins/metabolism , Gene Expression Regulation/drug effects , Nerve Tissue Proteins/metabolism , Tretinoin/pharmacology , Triiodothyronine/pharmacology , Analysis of Variance , Animals , Blotting, Western/methods , Brain/anatomy & histology , Brain/drug effects , Brain/metabolism , GAP-43 Protein/metabolism , In Situ Hybridization/methods , Male , Neurogranin , RNA, Messenger/metabolism , Rats , Rats, Wistar , Receptors, Retinoic Acid/metabolism , Reverse Transcriptase Polymerase Chain Reaction/methods , Tretinoin/blood , Triiodothyronine/bloodABSTRACT
Inflammatory exophthalmos with visual loss due to optic atrophy is reported in a 45-year-old man. Computed tomography showed an ethmoido-frontal mucocel. This single case stresses the severe complication of a mucocel like optic nerve head atrophy. The different tools for diagnosis and treatment are also emphasized.
