Levels of Delta-Opioid Receptor mRNA in Morphine-Tolerant Mice
- 1 January 1995
- journal article
- research article
- Published by Cognizant, LLC in Analgesia
- Vol. 1 (3) , 195-200
- https://doi.org/10.3727/107156995819564257
Abstract
Delta-opioid receptor (DOR) mRNA levels were studied in mice rendered tolerant to morphine after 3 days of repeated (tid) subcutaneous administration according to an escalating dosage schedule (10, 20, and 40 mg/kg on days 1, 2, and 3, respectively). ED50 determinations on day 4 demonstrate an approximately fourfold loss of morphine’s analgesic potency with the tail flick test. Utilization of a microdissection technique followed by quantitative solution hybridization of RNA extracts from brain and spinal cord revealed levels of DOR mRNA in control mice ranging from 3.8 pg/µg RNA in the caudate-putamen to 1.2 pg/µg RNA in the cerebellum. Neither the CNS levels of DOR mRNA nor the size of the DOR mRNA transcript differed when RNA extracts from tolerant and nontolerant mice from any CNS region were compared. The data indicate that alterations in DOR mRNA levels are not part of the adaptive changes resulting from chronic morphine administration and tolerance.Keywords
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