Expression of cholinergic markers in the pons of Flinders rats

The Flinders sensitive line of rats (FSL rats) have an altered REM sleep pattern which includes a shorter REM sleep latency and an increased percentage of REM sleep [R.M. Benca, D.H. Overstreet, M.A. Gilliland, D. Russell, B.M. Bergmann, W.H. Obermeyer, Increased basal REM sleep but no difference in dark induction or light suppression of REM sleep in Flinders rats with cholinergic supersensitivity, Neuropsychopharmacology 15 (1996) 45-51; P.J. Shiromani, D.H. Overstreet, D. Levy, C.A. Goodrich, S.A. Campbell, J. C. Gillin, Increased REM sleep in rats selectively bred for cholinergic hyperactivity, Neuropsychopharmacology 1 (1988) 127-133]. Cholinergic mechanisms have been implicated in REM sleep generation [reviewed in P.J. Shiromani, J.C. Gillin, S.J. Henriksen, Acetylcholine and the regulation of REM sleep: basic mechanisms and clinical implication for affective illness and narcolepsy, Annu. Rev. Pharmacol. Toxicol. 27 (1987) 137-156]. In the present study, specific aspects of the cholinergic system were examined in the pontine region of the FSL rats. The number of cholinergic neurons in the LDT and PPT were not different in FSL and control rats. Analysis of steady state levels of mRNAs encoding the acetylcholine synthesizing protein, choline acetyltransferase (ChAT) or the m2, m3 and m5 muscarinic receptor subtypes were also comparable in FSL and control rats. These data raise the possibility that the cellular events underlying the altered REM sleep pattern in FSL rats may include mechanisms that effect the muscarinic or nicotinic receptor in the pons.