The snoRNA MBII-52 regulates cocaine-induced conditioned place preference and locomotion in mice

Abstract

Cocaine dependence involves in the brain's reward circuit as well as nucleus accumbens (NAc), a key region of the mesolimbic dopamine pathway. Many studies have documented altered expression of genes and identified transcription factor networks and epigenetic processes that are fundamental to cocaine addiction. However, all these investigations have focused on mRNA and/or miRNA, which may not reflect the involvement of small nucleolar RNAs (snoRNAs), which has been implied in a broad range of biological processes and complex diseases including brain development and neuropathologocal process. To further address the role of snoRNA in cocaine addiction, we show that repeated exposure and conditioned place preference (CPP) training to cocaine negatively regulates the expression of MBII-52 mRNA level, which is a brain-specific C/D box snoRNA, but not influences the serotonin receptor 2C (5HT2CR) mRNA level in NAc. Furthemore, we show, developing lentiviral vector (LV)-expressing MBII-52 and LV-5HT2CR for stable and regulatable MBII-52 and LV-5HT2CR expression. LV-MBII-52 and LV-5HT2CR expression in NAc attenuate cocaine induced CPP and locomotor activity. Taken together, these findings show that MBII-52 and 5HT2CR exert an inhibitory influence on the behavioral responses to cocaine exposure.

Figure 1. Transcriptional regulation of MBII-52 and 5HT2CR by chronic cocaine in NAc.

Repeated cocaine administration, but not acute, significantly decreased MBII-52 (A) and not 5HT2CR (B) mRNA in NAc 24 h after the final drug injection compared with saline treatments (n = 6 mice per group; *p<0.05).

Figure 2. Cocaine CPP represses MBII-52 and 5HT2CR expression in NAc.

(A) Timeline of cocaine CPP experiment. Experimental design: S, saline; C, cocaine. (B) Conditioned place preference for cocaine. After conditioning, mice developed a significant preference for the cocaine-paired side. (n = 8, **P<0.01). Decreased expression of MBII-52 (C) and not 5HT2CR (D) mRNA in the NAc after cocaine-induce CPP. n = 8 and *P<0.05.

Figure 3. Virally expressed MBII-52 in the NAc regulates cocaine-induced CPP and locomotor activity.

(A) Verification of anatomical placement and viral infection in NAc after LV-MBII-52 EGFP injection; immunostaining for GFP is shown. (B) Virally expressed MBII-52 significantly attenuated cocaine-induced CPP. n = 10, *P<0.05 and **P<0.01. (C) MBII-52 mRNA level in the NAc of mice infected with LV-MBII-52 after cocaine CPP treatment. *P<0.05 and **P<0.01. (D) LV-MBII-52 significantly reduced the locomotor activity of the mice with repeated cocaine administration. n = 10, *P<0.05 and **P<0.01.

Figure 4. Virally expressed 5HT2CR in the NAc regulates cocaine-induced CPP and locomotor activity.

(A) Virally expressed 5HT2CR significantly attenuated cocaine-induced CPP. n = 10, **P<0.01. (B) 5HT2CR mRNA level in the NAc of mice infected with LV-5HT2CR after cocaine CPP treatment. **P<0.01. (C) LV-5HT2CR significantly reduced the locomotor activity of the mice with repeated cocaine administration. n = 10, **P<0.01.