Abstract
δ-Opioid agonists produce convulsions and antidepressant-like effects in rats. It has been suggested that the antidepressant-like effects are produced through a convulsant mechanism of action either through overt convulsions or nonconvulsive seizures. This study evaluated the convulsive and seizurogenic effects of nonpeptidic δ-opioid agonists at doses that previously were reported to produce antidepressant-like effects. In addition, δ-opioid agonist-induced electroencephalographic (EEG) and behavioral changes were compared with those produced by the chemical convulsant pentylenetetrazol (PTZ). For these studies, EEG changes were recorded using a telemetry system before and after injections of the δ-opioid agonists [(+)-4-[(αR)-α-[(2S,5R)-2,5-dimethyl-4-(2-propenyl)-1-piperazinyl]-(3-methoxyphenyl)methyl]-N,N-diethylbenz (SNC80) and [(+)-4-[α(R)-α-[(2S,5R)-2,5-dimethyl-4-(2-propenyl)-1-piperazinyl]-(3-hydroxyphenyl)methyl]-N,N-diethylbenzamide [(+)-BW373U86]. Acute administration of nonpeptidic δ-opioid agonists produced bilateral ictal and paroxysmal spike and/or sharp wave discharges. δ-Opioid agonists produced brief changes in EEG recordings, and tolerance rapidly developed to these effects; however, PTZ produced longer-lasting EEG changes that were exacerbated after repeated administration. Studies with antiepileptic drugs demonstrated that compounds used to treat absence epilepsy blocked the convulsive effects of nonpeptidic δ-opioid agonists. Overall, these data suggest that δ-opioid agonist-induced EEG changes are not required for the antidepressant-like effects of these compounds and that neural circuitry involved in absence epilepsy may be related to δ-opioid agonist-induced convulsions. In terms of therapeutic development, these data suggest that it may be possible to develop δ-opioid agonists devoid of convulsive properties.
Footnotes
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This work was supported by United States Public Health Service Grants DA00254, T32 GM07767, and T32 DA07267. This research also was supported in part by the Intramural Research Program of National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases.
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doi:10.1124/jpet.105.095810.
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ABBREVIATIONS: PTZ, pentylenetetrazol; (+)BW373U86, [(+)-4-[α(R)-α-[(2S,5R)-2,5-dimethyl-4-(2-propenyl)-1-piperazinyl]-(3-hydroxyphenyl-)methyl]-N,N-diethylbenzamide; EEG, electroencephalogram/electroencephalographic; AED, antiepileptic drug; ANOVA, analysis of variance; SNC80, [(+)-4-[(αR)-α-[(2S,5R)-2,5-dimethyl-4-(2-propenyl)-1-piperazinyl]-(3-methoxyphenyl)methyl]-N,N-diethylbenzamide.
- Received September 19, 2005.
- Accepted February 28, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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