Cocaine modulates mu-opioid receptor mRNA but not c-fos mRNA levels in primary cortical astrocytes

https://doi.org/10.1016/S0361-9230(02)00791-8Get rights and content

Abstract

Cocaine is known to modulate the opioid system in several brain regions, including the cortex. Glial cells that are derived from the neonatal cortex have been shown to express opioid peptides and opioid receptors. In this study we investigated the effects of cocaine on c-fos and mu-opioid receptor mRNA levels in primary cortical astrocyte cultures, using RT-PCR and quantitative solution hybridization assays. Astrocyte cultures from 1-day-old Fischer rats were untreated or treated with cocaine for 30 min, 2 h, or 5 h. While c-fos mRNA levels did not change at any time, mu-opioid receptor mRNA levels decreased by 75% after 2 and 5 h of cocaine treatments. Our data suggest that cocaine differentially modulates c-fos and opioid signaling in astrocyte cell culture.

Section snippets

INTRODUCTION

The opioid peptides, receptors, and their mRNA levels, are regulated by acute and chronic cocaine administration in several areas of the mesocorticolimbic and nigrostriatal pathways 8., 22., 26., 27.. Cocaine administration is shown to increase mu-opioid receptor (MOR) and decrease kappa opioid receptor (KOR) mRNA levels 25., 26., 27. while acute or intermittent cocaine administration increases mRNA and protein levels of several immediate early genes, including c-fos, which may be an initial

Primary Astrocyte Cultures

Primary astrocyte cells were established from the cortex of 1-day-old Fischer rats (Charles River, NY) as previously reported 5., 19.. Briefly, the brains of rat pups were removed and the cortex was dissected and counted by hemocytometer. The cells were seeded in 6 well tissue culture plates with an area of 9.6 cm2 per well (Falcon). Cells were grown for 2–3 weeks and the medium (Dubelcco’s modified eagle medium with l-glutamine, sodium pyruvate, and pyridoxine hydrochloride, containing 10% fetal

RESULTS

Figure 1 shows that more than 98% of the cultured cells expressed GFAP, indicating that they are astrocytes. Figure 2A–C show the effects of 30 min, 2 h, or 5 h of cocaine treatment, on MOR (top) and S16 (bottom) mRNA levels, respectively. Figure 2D shows the mean (±SEM) of MOR levels per S16 levels. Cocaine reduced MOR mRNA levels by 75% after 2 and 5 h of treatment as compared to untreated or 30 min cocaine treated cultures (Fig. 2D). There was no difference between the untreated and 30 min cocaine

DISCUSSION

Even though molecular mechanisms of MOR signaling are not clear, several reports have demonstrated an up-regulation of MOR mRNA levels in several mesocorticolimbic areas after cocaine administration as well as in astrocytes in culture after cytokine administration 19., 20., 26., 27.. However, MOR mRNA levels are significantly reduced after cocaine administration in developing rhesus macaque monkeys while etorphine and retinoic acid produce a biphasic effect on MOR mRNA levels, decreasing MOR

Acknowledgements

This work was supported in part by PS-CUNY, RCMI RR-03037, SCORE 506-GM 60654, MIDARP-DA12136, and SNRP NF-39534.

References (27)

  • A. Duttaroy et al.

    In vivo regulation of mu-opioid receptor density and gene expression in CXBX and outbred Swiss Webster mice

    Synapse

    (2000)
  • Fedoroff, S.; Richardson, A. Protocols for neuronal cell culture. Totowa, NJ: Humana Press;...
  • A.M. Graybiel et al.

    Amphetamine and cocaine induce drug-specific activation of the c-fos gene in striosome-matrix compartments and limbic subdivisions of the striatum

    Proc. Natl. Acad. Sci.

    (1990)
  • Cited by (5)

    • Toll-like receptors in chronic pain

      2012, Experimental Neurology
      Citation Excerpt :

      Importantly, proinflammatory central immune signaling events have been implicated in some of these behavioral consequences following opioid engagement of non-classical opioid systems. Nonetheless, immunocompetent cells within the CNS, including but not limited to, microglia (Bokhari et al., 2009; Chao et al., 1996, 1997; Horvath et al., 2010) and astrocytes (Bunn et al., 1985; Burbassi et al., 2010; Dobrenis et al., 1995; Festa et al., 2002; Hauser et al., 1996; Maderspach et al., 1995; Ruzicka et al., 1996; Thorlin et al., 1998) express opioid receptors. However, the role of the opioid receptor in initiating central immune signaling is unclear as it has been demonstrated that some TLRs (eg TLR2 and TLR4) are also capable of recognizing opioids.

    • Distribution of c-Fos immunoreactivity in the rat brain following abuse-like toluene vapor inhalation

      2012, Neurotoxicology and Teratology
      Citation Excerpt :

      However, the overall correspondence with anesthetics, as noted for the above-mentioned drugs of abuse, is imperfect, revealing a complex and unique pattern of brain activation during toluene vapor exposure. When interpreting neural activation inferred by c-Fos IR it must be recognized that c-fos can be induced in both neurons and glial cells (Edling et al., 2007), and select drugs of abuse including ethanol and LSD, but not cocaine, are in fact known to increase c-Fos IR in glial cells (Festa et al., 2002; Reissig et al., 2008; Yagle and Costa, 1999). Whereas toluene is well-known to negatively impact glial cells after long-term exposures, a condition known as toluene leukencephalopathy (Filley et al., 2004), the acute effects of toluene on glial cells have received less attention.

    • Pain and opioid addiction: What is the connection?

      2010, Current Pain and Headache Reports
    View full text