In the last decade, progress in gene disruption technology has allowed the study of the effects of the single-gene knockout (KO) on different molecules involved in the signaling cascade activated via muscarinic receptors. Many KO mice targeting muscarinic receptors have been developed, that is, all (M1-M5) muscarinic receptor KO mice (Wess, 2003) and acetylcholinesterase (AChE) KO mice(Xie et al., 2000). Recently, we have shown that these (AChE-/-) mice not only reveal changes in the number of muscarinic receptors in the heart, lung, cortex, and cerebellum but also in the number of adrenoceptors (Teplicky et al., 2004). Next, we studied whether the disruption of corticotropin-releasing hormone (CRH) or c-Fos could affect the properties of muscarinic receptors and adrenoceptors in the lungs and hearts of mice. The effects of immobilization stress in CRH KO animals were also studied.