Cobinamide is efficacious in treating neurotoxicity when administered up to 30 min after H2S exposure. (A and B) H2S-induced lesion severity with Cob treatment was observed up to 30 min after H2S exposure. Vacuolization, neurodegeneration, and gliosis are present in the inferior colliculus and, to a lesser extent, in the thalamus of animals exposed to H2S (arrows). * P < 0.05, ** P < 0.01 versus H2S/saline group. Representative photomicrographs of the inferior colliculus and thalamus (hematoxylin and eosin staining).