Calretinin terminals in the superior olivary nuclei. A: Transverse section through the medulla at the level of NM and SO, paired with a drawing to show the CR-ir tract connecting the first-order nuclei with the SO and SOv (black lines). CR-ir fibers delineate the projection to the ipsilateral SO and SOv, and to the contralateral SOv. B: Higher magnification view of CR-ir in SO and SOv. Arrows show the CR-ir fiber tracts to SO, between SO and SOv, and the midline decussation between first-order nuclei and contralateral SOv. C: Large CR-ir terminals in the SO. D: More rostral transverse section through the medulla at the level of NA and SOv shows CR-ir fibers that decussate and connect first-order nuclei and SOv (arrow). E: Enlarged view of the decussating CR-ir tract (arrows). F: Large CR-ir terminals in both the SO and the SOv; note large perisomatic boutons in SOv. G: Neurons in both SO and SOv are PV-ir, SO shown in horizontal section. H,I: CB-ir labeled neurons in SO. J: GAD-ir terminals in SO, both perisomatic and distributed through the neuropil. Scale bars = 500 at μm in A,B,D,E; 50 μm in C,F; 100 μm in G,H; 20 μm inl; 10 μm in J. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]