Differential time course of effects of [kappa]-opioid agonist treatment on dynorphin a levels and [kappa]-opioid receptor density

• Published in: Journal of molecular neuroscience 2004-06, Vol.24 (2), p.307
• Main Authors: D'addario, Claudio, Di Benedetto, Manuela, Izenwasser, Sari, Candeletti, Sanzio, Romualdi, Patrizia
• Format: Article
• Language: English
• Subjects: Rodents
• ISSN: 0895-8696; 1559-1166
• DOI: 10.1385/JMN:24:2:307

The effects of κ-opioid agonist treatment on κ-opioid receptor density and on dynorphin A levels in the rat brain were studied. Rats were treated with the selective κ-opioid agonist U-69593 or vehicle for 5 d. Dynorphin A levels and κ-opioid receptor binding were measured on day 8 (3 d after the last injection) or 22 (17 d after the last injection). On day 8, κ-opioid receptor density was increased in the hypothalamus of rats treated with U-69593; there were no changes in the frontal cortex or caudate putamen. In contrast, there was an increase in dynorphin A levels in the frontal cortex and no changes in hypothalamus and caudate putamen in response to U-69593. On day 22, B ^sub max^ was decreased in frontal cortex and caudate putamen of U-69593-treated rats, whereas dynorphin A levels were increased in the caudate putamen and in the frontal cortex. These findings suggest that κ-opioid receptor agonist treatment has long-term, continually changing effects on the κ-opioid system.[PUBLICATION ABSTRACT]