2,6‐Dichlorophenyl Methylsulphone Induced Behavioural Impairments in Rats and Mice in Relation to Olfactory Mucosal Metaplasia

2,6‐Dichlorophenyl methylsulphone (2,6‐diClPh‐MeSO 2 ) induces persistent olfactory mucosal metaplasia and a strong glial fibrillary acidic protein increase in the olfactory bulb of mice. Furthermore, 2,6‐diClPh‐MeSO 2 gives rise to a long‐lasting hyperactivity along with an impaired radial arm maze performance. To study cause‐effect relationships, olfactory mucosal histopathology, glial fibrillary acidic protein induction and neurobehavioural deficits were re‐examined in mice and rats of both sexes given a single intraperitoneal dose of 2,6‐diClPh‐MeSO 2 (16 and 65 mg/kg). There was a clear difference in the character of the olfactory mucosal lesions in the two species. In mice, an extensive metaplasia characterised by severe fibrosis, cartilage and bone formation accompanied with large polyps filling the nasal lumen was confirmed. In rats, a dose‐dependent weak metaplasia with patchy loss of olfactory epithelium was observed three weeks after dosing, preferentially at the dorsal meatus, nasal septum, and the tips of the middle ethmoturbinates. Large areas of intact olfactory epithelium remained in all animals, particularly in the low dose rats. In both species, 2,6‐diClPh‐MeSO 2 gave rise to significantly increased motor‐activities, impaired performance in the radial arm maze, and glial fibrillary acidic protein‐induction. Only rats showed hyperactivity at the low dose. Performance in the Morris water maze was unaffected in rats of both sexes indicating that a general impairment in spatial learning could not be supported. We propose that the observed hyperactivity and radial arm maze acquisition deficits originated from a direct effect of 2,6‐diClPh‐MeSO 2 in the brain rather than being a consequence of the olfactory mucosal lesion.