Cytochrome oxidase activity in the olfactory system of staggerer mutant mice

The staggerer mutation is characterized by the disruption of a single recessive gene encoding for the nuclear hormone receptor RORalpha. In addition to the well-studied gene expression in the cerebellum causing massive primary Purkinje cell loss, the RORalpha gene is also expressed in the thalamus and the olfactory bulb. A quantitative histochemical study of cytochrome oxidase activity was performed in staggerer mutants and their respective controls in order to determine whether olfactory bulb neuropathology leads to neuronal metabolic alterations in olfactory and related limbic regions. In the staggerer olfactory bulb, the core and the shell of the glomeruli had lower levels of cytochrome activity, whereas higher levels were found in the external plexiform and granular layers. Other olfactory and limbic regions were unchanged, except for a higher level in the accessory olfactory bulb and a lower level in the most ventral part of the medial orbital cortex. These results are discussed with regard to the olfactory deficits and changes in social interactions previously observed in this mutant.