OR-Z6-positive glomeruli in H-lacZ6 mice receive input from two phenotypically different ORN populations. IHC for β-galactosidase and in situ hybridization for OR-Z6 were performed on separate but adjacent sets of coronal cryosections (15 μm) cut from the OB of a P26 H-lacZ6 mouse. The panelsshow a series of higher magnifications of the ventromedial portion of the left OB. The order in which sections were taken along the anterior-to-posterior axis is indicated by the numbers 1–6. Hybridization signals for OR-Z6 appear as dense white grains (dark-field, left), whereas β-gal⁺ axons are visible asbrown fibers entering their target glomeruli (bright-field, right). Corresponding glomeruli in adjacent sections were aligned after identifying glomerular borders by counterstaining periglomerular nuclei. Comparison of labeled glomeruli in the two columns demonstrates that theOR-Z6⁺ glomerulus receives input from β-gal⁺ axons as well (white boxed areas). The changing signal intensity for bothOR-Z6 and β-gal as the sections progress through the different depths of the glomerulus can be traced along the anterior-to-posterior axes of the three sections shown. Note the small number of β-gal⁺ axons projecting to theOR-Z6-labeled glomerulus. Scale bar, 100 μm.