Fig. 1. Northern blot analyses of CXBK mouse brain mRNAs.A, mRNAs (1.5 μg) of B6 and CXBK (CX) mouse brains were hybridized with cDNA probes for μ-OR mRNA. The size of the detected band in the CX lane was estimated at 14.5 kb (arrow), whereas that in the B6 lane was at 12 kb (arrowhead). B, mRNAs (4 μg) of B6, heterozygote (He) between B6 and CXBK, CXBK (CX), and BALB/c (BA) mouse brains were analyzed with cDNA probes for μ-, δ-, and κ-ORs. The sizes of μ-OR probe-positive bands in the B6 and BA lanes were estimated at 12 kb and that in the CX lane was at 14.5 kb. The ratios of the signal intensities for the μ-OR probe in the He, CX, andBA lanes to the intensity in the B6 lanewere 0.75, 0.6, and 1.1, respectively. The ratios of the signal intensity for the δ-OR probe in the He,CX, and BA lanes to the intensity in theB6 lane were 1.1, 1.7, and 1.4, respectively. The signal intensities for the κ-OR probe in all lanes were even. Thenumbers next to the photographs indicate the RNA size in kilobases.