| Abstract: |
Chronic treatment with opioid antagonists increases the potency of opioid agonists and produces an increase in brain opioid binding sites. In the present study, 8 day treatment with naltrexone blocked morphine and DADLE analgesia for the entire treatment period and increased μ1, μ2 and δ opioid receptor binding sites in mouse brain. μ1 and μ2 binding were increased by 81 and 67%, respectively, while δ binding was increased by 31%. Consistent with these binding changes, the potency of ICV morphine to produce analgesia was increased by over 3-fold, while the potency of ICV DADLE was increased by only 1.7. These findings indicate that relative increases in opioid receptor subtypes agree with pharmacodynamic studies on potency changes of opioid agonists. © 1988. |
| Keywords: |
nonhuman; mouse; animal; mice; pain; animal experiment; drug receptor binding; brain; morphine; analgesia; receptors, opioid, mu; opiate receptor; naltrexone; receptors, opioid, delta; subcutaneous drug administration; receptors, opioid; intracerebroventricular drug administration; male; priority journal; enkephalin, leucine-2-alanine; support, u.s. gov't, p.h.s.; enkephalin[2 dextro alanine 5 dextro leucine]; enkephalin, leucine
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