EXPRESSION OF CHOLINERGIC MUSCARINIC RECEPTOR SUBTYPES MESSENGER-RNA IN RAT-BLOOD MONONUCLEAR-CELLS

The cholinergic system plays a role in the neuroimmune network. White blood cells have been found to express muscarinic and nicotinic cholin ergic receptors as well as acetylcholinesterase on their surface, and cholinergic agents have been shown to modulate immune functions. Altho ugh the presence of muscarinic receptors on white blood cells has been well documented by binding and functional studies, the subtype(s) of muscarinic receptor present on these cells is still unknown. We have p reviously shown the absence of m2 muscarinic receptor subtype mRNA in rat mononuclear cells (Costa et al., 1994). The expression of m1, m3, m4 and m5 mAChR mRNA was analyzed in this study in rat peripheral bloo d mononuclear cells by Northern blotting hybridization experiments and reverse transcription-polymerase chain reaction. Only mRNA of the m3 subtype was detected in rat mononuclear cells, at levels about 100 tim es lower than in brain. Traces of m4 subtype mRNA were found in lympho cytes, at levels about 10 000 times lower than the cerebral cortex, wh ile m5 mRNA was undetectable.