Muscarinic receptor subtypes expression in rat and chick dorsal root ganglia

In the present work we have analyzed by Northern blot, RT-PCR and in situ h ybridization the expression of muscarinic receptor subtype mRNAs in rat and chick dorsal root ganglia. Northern blot analysis performed on rat total R NA revealed a strong signal for M-2 while a faint band was observed for M-3 and M-4 subtypes; no signal was evident for M-1 and M-5, while in chick to tal RNA no signal was detected for any of the analyzed subtypes (M-2, M-3, M-4). On the other hand, RT-PCR revealed that all muscarinic subtype mRNAs were present both in rat and chick DRG, although the level of their express ion may be different. In chick DRG, the presence of various muscarinic subt ypes was confirmed by competition binding experiments. In situ hybridizatio n in rat DRG showed that M-2 and M-2 transcripts, similarly to what has bee n previously described for M-2 mRNA, were preferentially localized in mediu m-small neurons. Large neurons were usually negative or faintly labelled. N o hybridization signal was detected in rat DRG with probes for M, and Mj mu scarinic subtypes. The presence of various muscarinic receptors in DRG and their preferential expression in the medium-small sensory neurons suggest t heir possible involvement in the modulation of nociceptive stimuli transduc tion. (C) 2000 Elsevier Science B.V. All rights reserved.