Representative pictures of prairie vole MOR in situ hybridization (1.1 A, D, G, J; 1.2 A, D, G, J; and 1.3 A, D, G), ligand binding autoradiography (1.1 B, E, H, K; 1.2 B, E, H, K; and 1.3 B, E, H), and acetylcholinesterase staining (1.1 C, F, I, L; 1.2 C, F, I, L; and 1.3 C, F, I) for anatomical reference. Coronal sections in rostral-caudal order: 1.1, from olfactory bulbs to septum; 1.2, from thalamus to substantia nigra; and 1.3, from periaqueductal gray to cerebellum. Fig. 1.3 contains sagittal section pictures of in situ hybridization with antisense- (M) or sense- (N) probe, demonstrating specificity of the antisense probe. See Table 1 for abbreviations. Scale bars in 1.1 L, 1.2 L, 1.3 I, and 1.3 N = 1mm