Chronic nicotine treatment decreases neurofilament immunoreactivity in the rat ventral tegmental area

Region-specific decreases of neurofilament proteins have been described in the ventral tegmental area of rats chronically treated with either morphine or cocaine. The aim of the present study was to assess if the levels of neurofilament proteins are changed in the ventral tegmental area by chronic treatment with nicotine. Immunoreactivity for NF-68, NF-160 and NF-200 was determined using NR4, BF10 and RT97 antibodies, respectively. Measurements were performed using computer-assisted microdensitometry of brain sections from rats exposed to chronic nicotine treatment (0.4 mg/kg/dayx6 days) or to saline. Chronic nicotine treatment reduced NF-160 and NF-200 immunoreactivity by 44.5% (P<0.01) and 22.5% (P<0. 05), respectively, in the ventral tegmental area but not in the substantia nigra. A trend towards reduction was observed for NF-68 immunoreactivity in the ventral tegmental area. These preliminary results suggest that nicotine shares the same properties with cocaine and morphine to reduce neurofilament proteins in the ventral tegmental area, a key brain structure of the reward system.