As mentioned above, in contrast to embryonic animals, all four founder lines exhibited significant β-gal staining at one month of age. Analysis of β-gal staining revealed broad and substantial β4 promoter activity in the brains of transgenic animals. In particular, there was significant staining in the cortex, hippocampus, thalamus, amygdala, medial habenula and the colliculus. For the most part, the broad β-gal staining (Table 3) is consistent with previous studies that determined β4 subunit mRNA expression using in situ hybridization (Azam et al., 2002; Dineley-Miller and Patrick, 1992; Winzer-Serhan and Leslie, 1997). In addition, the present results are consistent with immunostaining work that indicated widely dispersed expression of the nACh receptor β4 subunit protein in the adult mouse nervous system (Gahring et al., 2004). As discussed by Gahring et al., the regulated widespread expression of the β4 subunit gene likely reflects its role in a variety of diverse functions in the nervous system.
