RGD Reference Report - Effect of morphine on proopiomelanocortin gene expression and peptide levels in the hypothalamus. - Rat Genome Database

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Effect of morphine on proopiomelanocortin gene expression and peptide levels in the hypothalamus.

Authors: Wardlaw, S L  Kim, J  Sobieszczyk, S 
Citation: Wardlaw SL, etal., Brain Res Mol Brain Res. 1996 Sep 5;41(1-2):140-7. doi: 10.1016/0169-328x(96)00084-8.
RGD ID: 405878077
Pubmed: PMID:8883945   (View Abstract at PubMed)
DOI: DOI:10.1016/0169-328x(96)00084-8   (Journal Full-text)

Opiates have been reported to suppress POMC in the medial basal hypothalamus (MBH) but studies have been complicated by the fact that acutely, in the rat, opiates stimulate corticosterone and inhibit gonadal steroid release, which could both affect POMC in brain. We have therefore examined POMC gene expression and peptide levels in the MBH of castrated rats after 10 days of treatment with subcutaneous morphine or placebo pellets and after pellet removal. POMC mRNA was measured by solution hybridization assay and beta-endorphin (beta-EP) and alpha-MSH were measured by RIA. In castrated male rats, the mean POMC mRNA concentration in the MBH was 1.67 +/- 0.11 pg/microgram RNA in the control animals and decreased to 1.17 +/- 0.11 pg/microgram RNA in the morphine-treated animals (P < 0.01). Similarly in castrated, estradiol replaced female rats, the mean POMC mRNA level in the MBH was 1.36 +/- 0.19 pg/microgram RNA and decreased to 0.82 +/- 0.08 pg/microgram RNA after morphine treatment (P < 0.05). beta-EP levels were not significantly different in either study. When castrated male rats were similarly morphine pelleted and killed either on day 10 or 2 days later after pellet removal, the mean POMC mRNA level again fell from 1.83 +/- 0.21 in the controls to 1.28 +/- 0.20 pg/microgram RNA after 10 days of morphine; 2 days after pellet removal levels remained suppressed at 0.80 +/- 0.08 pg/microgram RNA (P < 0.01). In this study the concentrations of beta-EP and alpha-MSH were both noted to decline in the MBH after morphine treatment (P < 0.05). When the forms of beta-EP in the MBH were characterized by HPLC, a decrease in the concentration of beta-EP was again seen after morphine but no significant differences in the pattern of beta-EP processing or in the relative amounts of beta-EP1-31 compared to beta-EP1-27 and beta-EP1-26 were noted in morphine-treated animals. There was also no significant effect of 10(-6)-10(-4) M morphine on basal or KCl-stimulated release of beta-EP or gamma 3-MSH release from the perifused rat hypothalamus in vitro. We conclude that morphine suppresses POMC gene expression in the hypothalamus of chronically treated male and female rats. Persistent changes were also noted during morphine withdrawal. In some cases this was accompanied by a fall in beta-EP peptide content. These effects were seen in castrated animals with and without sex steroid replacement and are thus independent of the effects of morphine on the pituitary-gonadal axis. These results show that opiate drugs modify endogenous opioid systems in the brain and provide further support for the hypothesis that such changes may contribute to mechanisms of opiate dependence and withdrawal.



RGD Manual Disease Annotations    Click to see Annotation Detail View

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
POMCHumanmorphine dependence  ISOPomc (Rattus norvegicus)mRNA:decreased expression:hypothalamusRGD 
PomcRatmorphine dependence  IEP mRNA:decreased expression:hypothalamusRGD 
PomcMousemorphine dependence  ISOPomc (Rattus norvegicus)mRNA:decreased expression:hypothalamusRGD 
POMCHumanmorphine withdrawal syndrome  ISOPomc (Rattus norvegicus)mRNA:decreased expression:hypothalamusRGD 
PomcRatmorphine withdrawal syndrome  IEP mRNA:decreased expression:hypothalamusRGD 
PomcMousemorphine withdrawal syndrome  ISOPomc (Rattus norvegicus)mRNA:decreased expression:hypothalamusRGD 

Objects Annotated

Genes (Rattus norvegicus)
Pomc  (proopiomelanocortin)

Genes (Mus musculus)
Pomc  (pro-opiomelanocortin-alpha)

Genes (Homo sapiens)
POMC  (proopiomelanocortin)


Additional Information