Date of Award

5-2003

Degree Type

Thesis

Degree Name

MS Biology

Department

Biology

Advisor

Sulie L. Chang

Committee Member

Allan D. Blake

Committee Member

Hsien-Ching Liu

Keywords

Mu opioid receptor mRNA, SHSY-5Y human neuroblastoma cells

Abstract

Prolonged exposure to morphine down-regulates mu opioid receptors (MOR) on both undifferentiated and differentiated (retinoic acid or phorbol ester treated) SHSY-5Y cells. However, morphine pretreatment does not alter MOR receptor affinity for morphine. To investigate the molecular basis for MOR regulation after exposure to its selective agonists, we have developed a quantitative competitive reverse transcriptase-polymerase chain reaction (QC-RT PCR) to quantify the expression of MOR in SHSY-SY cells. Differentiation of SHSY-5Y cells with retinoic acid or phorbol ester up regulated MOR mRNA expression by 30 % and 78%, respectively. A 24 hours treatment with morphine (10 µM) down regulated MOR mRNA, an effect that was partially reversed by naloxone. However, after exposure to endomorphin-1, 2 for 24 hours, MOR mRNA expression is significantly increased in the differentiated and non-differentiated SHSY-5Y cells. Differences in intracellular cAMP accumulation are also observed in the differentiated and non-differentiated SHSY-5Y cells after the chronic exposure to morphine and endomorphin-1,-2. Taken together, a significant component of SHSY-5Y cellular adaptation during chronic morphine treatment may occur at the mRNA level and our data suggest different morphine or endomorphin-1, -2 mediated molecular events in the MOR receptor regulation.

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