Differential properties between TRK-820 and U-50,488H on the discriminative stimulus effects in rats.
It has been demonstrated that the newly synthesized kappa-opioid receptor agonist TRK-820, which has a unique structure that is different from those of other prototypical kappa-opioid receptor agonists such as U-50,488H, exert some behavioral effects that differ from those induced by U-50,488H. Therefore, the present study was designed to examine the possible difference between the discriminative stimulus effects of TRK-820 and U-50,488H in rats. Substitution tests with several kappa-opioid receptor agonists were initiated in rats trained to discriminate between TRK-820 (40 microg/kg) or U-50,488H (3.0 mg/kg) and saline. In the cross-substitution tests, U-50,488H substituted for the discriminative stimulus effects of TRK-820, whereas TRK-820 did not substitute completely for those of U-50,488H, indicating that the discriminative stimulus effects of TRK-820 and U-50,488H were somewhat different. In the substitution tests, E-2078, but not R-84760, substituted for the discriminative stimulus effects of both TRK-820 and U-50,488H. KT-90, CI-977 and ICI-199441 each substituted for the discriminative stimulus effects of U-50,488H, but not to those of TRK-820. These results imply that these kappa-opioid receptor agonists possess U-50,488H-like discriminative stimulus effects. Furthermore, that U-50,488H and the other kappa-opioid receptor agonists substituted for the discriminative stimulus effects of U-50,488H, produced aversive effects in rats. These findings suggest the possibility that unlike those of TRK-820, the cue of the discriminative stimulus effects of U-50,488H may be, at least in part, associated with its aversive effects.
Mori
Tomohisa
T
Department of Toxicology, Hoshi University School of Pharmacy and Pharmaceutical Science, Shinagawa-ku, Tokyo 142-8501, Japan.
Nomura
Mutsuko
M
Yoshizawa
Kazumi
K
Nagase
Hiroshi
H
Narita
Minoru
M
Suzuki
Tsutomu
T
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology*; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D000818:Animals; D004193:Discrimination Learning / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D008297:Male; D009019:Morphinans / Q000494:pharmacology*; D051381:Rats; D011916:Rats, Inbred F344; D017473:Receptors, Opioid, kappa / Q000819:agonists*; D013141:Spiro Compounds / Q000494:pharmacology*
D018712:Analgesics, Non-Narcotic; D009019:Morphinans; D017473:Receptors, Opioid, kappa; D013141:Spiro Compounds; C111212:TRK 820; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer