RT-PCR reveals muscarinic acetylcholine receptor mRNA in the pre-Botzingercomplex

Muscarinic receptors mediate the postsynaptic excitatory effects of acetylc holine (ACh) on inspiratory neurons in the pre-Botzinger complex (pre-BotC) , the hypothesized site for respiratory rhythm generation. Because pharmaco logical tools for identifying the subtypes of the muscarinic receptors that underlie these effects are limited, we probed for mRNA for these receptors in the pre-BotC. We used RT-PCR to determine the expression of muscarinic receptor subtypes in tissue punches of the pre-BotC taken from rat medullar y slices. Cholinergic receptor subtype M-2 and M-3 mRNAs were observed in t he first round of PCR amplification. All five subtypes, M-1-M-5, were obser ved in the second round of amplification. Our results suggest that the majo rity of muscarinic receptor subtypes in the pre-BotC are M-2 and M-3, with minor expression of M-1, M-4, and M-5.