Cerebellar neuronal apoptosis in heroin-addicted rats and its molecular mechanism

The overall objective of this study was to investigate neuronal apoptosis and expression of apoptosis related proteins (c-jun, cytc and Bax) in the cerebellum of rates with heroin addiction.

40 adult male Sprague-Dawley rats which weighing 200-220 g were randomly divided into 5 groups (n = 8 per group): control group, 10-day heroin-addicted group, 20-day heroin-addicted group, 30-day heroin-addicted group and 40-day heroin-addicted group. Rats in the control group were treated with normal saline. Rats in the addiction groups (20 d, 30 d, 40 d) were all given subcutaneous injection with heroin for 15 days to induce heroin addiction. After injected with heroin for 15 days, rats were treated with naloxone at a dose of 5 mg/kg to induce abstinence for 30 mins to examine the addiction of rats. They were then continued to be treated with heroin for another 10 days, 20 days, 30 days, and 40 days respectively to establish heroin-addicted models. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) was employed to identify apoptotic cells [6]. Immunohistochemistry and Western blot assay were also used in the study to examine the protein expressions of c-jun, cytc and Bax in the cerebellum.

Compared with the control group, the proportion of apoptotic neurons increased significantly in the heroin addiction groups (10 d, 20 d, 30 d, 40 d) (P < 0.05), also accompanied by markedly increased expressions of c-jun, cytc and Bax (P < 0.05) depending on doses of heroin in the cerebellum. Thus, the significant differences were observed in heroin addiction groups (10 d, 20 d,30 d, 40 d) and control group (P < 0.05).

Long-term use of heroin may induce neuronal apoptosis in the cerebellum by raising the expressions of pro-apoptotic c-jun, cytc and Bax, which might be one of mechanisms underlying the heroin-induced cerebellum neuronal damage.