1.
Ploj, Karolina, et al.
(författare)
Basal levels and alcohol-induced changes in nociceptin/orphanin FQ, dynorphin, and enkephalin levels in C57BL/6J mice
2000
Ingår i: Brain Research Bulletin. - 0361-9230 .- 1873-2747. ; 53:2, s. 219-226
Tidskriftsartikel (refereegranskat) abstract
In order to investigate the involvement of the opioid and nociceptin/orphanin FQ (N/OFQ) system in alcohol drinking behaviour, N/OFQ and the opioid peptides dynorphin B (DYNB) and Met-enkephalin-Arg(6) Phe(7) (MEAP) were examined in the alcohol-preferring C57BL/6J mice. Basal peptide levels were compared in the brain and the pituitary gland with basal levels in the alcohol-avoiding DBA/2J mice. Furthermore, the effects of chronic alcohol self-administration on peptides were studied in the C57BL/6J mice. Compared to the DBA/2J mice, C57BL/6J mice had low immunoreactive (ir) levels of DYNB and MEAP in the nucleus accumbens, the hippocampus, and the substantia nigra, low ir-DYNB levels in the striatum and low ir-MEAP levels in the frontal cortex. Higher ir-DYNB levels in the pituitary gland and in the periaqueductal gray (PAG) and higher ir-N/OFQ levels in the frontal cortex and in the hippocampus were detected in C57BL/6J mice compared to the DBA/2J mice. After 4 weeks of voluntary alcohol consumption, only minor changes in steady-state peptide levels were identified. However, 5 days after the alcohol-drinking period, lower levels of all peptides were detected in the ventral tegmental area and ir-DYNB levels were also lower in the amygdala and in the substantia nigra. Twenty-one days after cessation of alcohol self-administration, the opioid peptides in alcohol-consuming C57BL/6J mice were lower in the PAG, the N/OFQ was lower in the frontal cortex and DYNB was higher in the amygdala and substantia nigra as compared to control C57BL/6J mice. This study demonstrates strain differences between C57BL/6J mice and DBA/2J mice that could contribute to divergent drug-taking behaviour, and it also demonstrates time- and structure-specific changes in neuropeptide levels after alcohol self-administration in the C57BL/6J mice.
2.
Lindholm, Sara, et al.
(författare)
Repeated ethanol administration induces short- and long-term changes in enkephalin and dynorphin tissue concentrations in rat brain
2000
Ingår i: Alcohol. - 0741-8329 .- 1873-6823. ; 22:3, s. 165-171
Tidskriftsartikel (refereegranskat) abstract
Recently, we have shown that rats repeatedly treated with ethanol and/or cocaine have decreased kappa-opioid receptor mRNA levels in the mesolimbic system. The aim of the present study was to investigate the short- and long-term effects of repeated ethanol administration on opioid peptide concentrations in brain tissue of male Sprague-Dawley rats. Dynorphin B (1-13) (Dyn B) and Met-enkephalinArg(6)Phe(7) (MEAP), endogenous ligands to kappa- and delta-opioid receptors, respectively, were measured using radioimmunoassays. The rats were given either ethanol [intraperitoneal (ip), twice daily, 2 g/kg bw/dose] or saline for 13 consecutive days. Thirty minutes after the last ethanol dose on Day 13, the Dyn B tissue concentration was significantly decreased in the cingulate cortex. The MEAP tissue concentration was decreased in the hippocampus 5 days after the last ethanol injection as compared to saline-treated controls. Furthermore, the Dyn B and the MEAP concentrations were increased in the periaqueductal grey area (PAG) at this time point. Of particular interest were the significant increases in Dyn B tissue concentrations found in the nucleus accumbens (NAcc) at 30 min and at 21 days after the last ethanol dose. The results suggest that repeated ethanol administration induces both short- and long-term changes in the tissue concentrations of opioids in certain brain regions associated with motivation and reward.
