Age‐related loss of neuronal nicotinic receptor expression in the aging mouse hippocampus corresponds with cyclooxygenase‐2 and PPARγ expression and is altered by long‐term NS398 administration

Age‐related changes in the mammalian dorsal hippocampus are associated with diminished expression of neuronal nicotinic acetylcholine receptors (nAChR), which is particularly severe in pathologies such as those associated with dementias, including Alzheimer's disease. Because the mouse is a useful model for age‐related decline in nAChR expression in the basal forebrain and limbic system, we used immunohistochemistry to examine the influence of long‐term (12‐month) oral administration of nicotine and/or the cyclooxygenase‐2 (COX‐2) preferring non‐steroidal anti‐inflammatory drug (NSAID) NS398 on nAChRα4, α5, α7, and β4 expression in the C57BL/6 mouse. Inhibitory neurons of the dorsal hippocampus that express nAChRs also constitutively express COX‐2 and the peroxisome proliferator‐antagonist receptor subtype gamma‐2 (PPARγ2) which is also a target of NS398. Administration of NS398 correlated with retention of nAChRα4 and to a lesser extent nAChRβ4, but not nAChRα5 or α7, but nicotine exhibited no similar effect. Nicotine and NS398 co‐administration abolished the NS398‐related effect on nAChRα4 retention. These results provide evidence that the interaction during aging between oral administration of nicotine and NSAIDs are not straightforward and could even be antagonistic when combined. © 2004 Wiley Periodicals, Inc. J Neurobiol, 2005