Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2013 Jun 11;8(6):e66438.
doi: 10.1371/journal.pone.0066438. Print 2013.

Differential regulation of the period genes in striatal regions following cocaine exposure

Edgardo Falcon  1 , Angela Ozburn, Shibani Mukherjee, Kole Roybal, Colleen A McClung
Affiliations

Differential regulation of the period genes in striatal regions following cocaine exposure

Edgardo Falcon et al. PLoS One. .

Abstract

Several studies have suggested that disruptions in circadian rhythms contribute to the pathophysiology of multiple psychiatric diseases, including drug addiction. In fact, a number of the genes involved in the regulation of circadian rhythms are also involved in modulating the reward value for drugs of abuse, like cocaine. Thus, we wanted to determine the effects of chronic cocaine on the expression of several circadian genes in the Nucleus Accumbens (NAc) and Caudate Putamen (CP), regions of the brain known to be involved in the behavioral responses to drugs of abuse. Moreover, we wanted to explore the mechanism by which these genes are regulated following cocaine exposure. Here we find that after repeated cocaine exposure, expression of the Period (Per) genes and Neuronal PAS Domain Protein 2 (Npas2) are elevated, in a somewhat regionally selective fashion. Moreover, NPAS2 (but not CLOCK (Circadian Locomotor Output Cycles Kaput)) protein binding at Per gene promoters was enhanced following cocaine treatment. Mice lacking a functional Npas2 gene failed to exhibit any induction of Per gene expression after cocaine, suggesting that NPAS2 is necessary for this cocaine-induced regulation. Examination of Per gene and Npas2 expression over twenty-four hours identified changes in diurnal rhythmicity of these genes following chronic cocaine, which were regionally specific. Taken together, these studies point to selective disruptions in Per gene rhythmicity in striatial regions following chronic cocaine treatment, which are mediated primarily by NPAS2.

PubMed Disclaimer

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Clock, Npas2 and Bmal1 expression after cocaine treatment.
Real-time PCR analysis of Clock, Npas2, and Bmal1 expression in the CP and NAc following saline, acute (15 mg/kg, 1 day), or chronic cocaine treatment (15 mg/kg, 7 days) in wild type mice. *p<0.05 by t-test, n = 6.
Figure 2
Figure 2. Per gene and protein expression after cocaine treatment.
Real-time PCR analysis of mPer1, mPer2 and mPer3 expression in the CP (A) and NAc (B) following saline, acute (15 mg/kg, 1 day), or chronic cocaine treatment (15 mg/kg, 7 days) in wild type mice. *p<0.05, **p<0.01 by t-test. n = 6. (C, D) Cocaine (15 mg/kg) or saline was given chronically (7 days) i.p. Protein levels were measured 24 hrs later using western blot analysis in the CP and NAc. GAPDH was measured as a loading control. n = 5–8. Representative blots are shown (C) and the percent change in cocaine vs saline is shown (D). *p<0.05, **p<0.01 by t-test.
Figure 3
Figure 3. Binding of NPAS2 and CLOCK to the Per promoters in striatal regions.
ChIP assays were performed with antibodies specific to CLOCK, NPAS2, and acetylated histone H3. IgG was used as a negative control. This was followed by real-time PCR analysis using primers specific to the mPer1, mPer2, or mPer3 promoters.(A) ChIP assays were performed in NAc and CP tissue using an antibody for NPAS2 in animals treated chronically with cocaine (15 mg/kg, 7 days) or saline. Shown are the fold changes in cocaine treated animals versus saline treated animals. (B) ChIP assays were performed in NAc and CP tissue using an antibody for CLOCK in animals treated chronically with cocaine (15 mg/kg, 7 days) or saline. Shown are the fold changes in cocaine treated animals versus saline treated animals (Fold ±1). **p<0.01, ***p<0.001 by t-test (cocaine vs. saline), n = 6.
Figure 4
Figure 4. Effect of the Npas2 mutation on Per gene induction following cocaine.
Real-time PCR analysis of mPer1, mPer2, and mPer3 expression in the CP and NAc following chronic treatment (15 mg/kg, 7 days) with saline or cocaine in wild type and Npas2 mutant mice. Shown are the fold changes in cocaine treated animals relative to saline treated animals. *p<0.05, **p<0.01, ***p< 0.001 by t-test. n = 5.
Figure 5
Figure 5. Chronic cocaine alters Npas2 rhythmic expression only in the NAc, whereas Clock is unchanged.
(A) Clock gene expression (mean ± SEM, n =  6–9) in the NAc and CP is unaltered by chronic cocaine (B) Npas2 rhythmicity in the NAc is abolished following chronic cocaine and a significant upregulation was observed at ZT 4 (*p<0.05). Dark background indicates lights-off.
Figure 6
Figure 6. Chronic cocaine alters diurnal expression of Per genes in the NAc and CP.
(A) Cocaine alters mPer1 expression (mean ± SEM, n = 6–9) in the NAc and CP. Rhythmicity of mPer1 is maintained in the NAc but abolished in the CP following cocaine treatment. A significant upregulation at ZT4 was observed in both regions (*p<0.05). (B) mPer2 rhythmicity is unaltered in the NAc but disrupted in the CP following cocaine. A significant upregulation at ZT 4 was observed only in the CP (*p<0.05). (C) While rhythmicity is maintained, mPer3 is highly upregulated in the NAc. Cocaine disrupts rhythmicity of mPer3 in the CP.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Wasielewski JA, Holloway FA (2001) Alcohol's interactions with circadian rhythms. A focus on body temperature. Alcohol Res Health 25: 94–100. - PMC - PubMed
    1. Jones EM, Knutson D, Haines D (2003) Common problems in patients recovering from chemical dependency. Am Fam Physician 68: 1971–1978. - PubMed
    1. Iijima M, Nikaido T, Akiyama M, Moriya T, Shibata S (2002) Methamphetamine induced, suprachiasmatic nucleus-independent circadian rhythms of activity and mPer gene expression in the striatum of the mouse. Eur J Neurosci 16: 921–929. - PubMed
    1. Stephan FK (1984) Phase shifts of circadian rhythms in activity entrained to food access. Physiol Behav 32: 663–671. - PubMed
    1. Nestler EJ (2005) Is there a common molecular pathway for addiction? Nat Neurosci 8(11): 1445–1449. - PubMed

Publication types

MeSH terms

LinkOut - more resources