Abstract

Long-sleep (LS) and short-sleep (SS) mice show differential sensitivity to both acute and chronic ethanol administration. Previous data also showed differential behavioral responses to muscarinic acetylcholine receptor agonist or antagonist treatment. We now report significantly greater inductions of c-fos, c-jun, jun-B, and Egr-1, but not jun-D, mRNA in the central nervous system (CNS) of LS versus SS mice after the intraperitoneal administration of oxotremorine. These genomic responses were dose dependent and completely inhibited (in both strains) by scopolamine, a specific muscarinic receptor antagonist. In situ hybridization studies verified the greater immediate early gene (IEG) inductions in LS mice, as initially observed by Northern analysis, and specifically showed that c-fos mRNA induction occurred predominantly in the thalamus, olfactory bulb, cerebellum, and cerebral cortex. Oxotremorine-induced c-jun mRNA was increased in cerebellum, CA1 hippocampal field, and cerebral cortex of both strains. Induced jun-B and Egr-1 transcripts were determined to have very similar CNS distribution patterns. Both mRNA species were induced in the cerebral cortex, caudate nucleus and putamen, hippocampal structures, and olfactory bulb. To further determine whether these differential IEG inductions reflect regional differences in receptor numbers, we determined the distributions and levels of each of the five muscarinic receptor subtypes in both strains by in situ hybridization. These data show that differences in receptor numbers alone may not account for the differential IEG inductions observed between the strains. Differential coupling constraints among CNS muscarinic receptors in LS versus SS mouse CNS may also play a significant role in producing differential IEG inductions.