Details

Autor(en) / Beteiligte

• Mori, Tomohisa
• Nomura, Mutsuko
• Yoshizawa, Kazumi
• Nagase, Hiroshi
• Narita, Minoru
• Suzuki, Tsutomu

Titel

Differential properties between TRK-820 and U-50,488H on the discriminative stimulus effects in rats

Ist Teil von

• Life sciences (1973), 2004-10, Vol.75 (20), p.2473-2482

Ort / Verlag

Netherlands: Elsevier Inc

Erscheinungsjahr

2004

Quelle

Elsevier ScienceDirect Journals

Beschreibungen/Notizen

• It has been demonstrated that the newly synthesized κ-opioid receptor agonist TRK-820, which has a unique structure that is different from those of other prototypical κ-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 κ-opioid receptor agonists were initiated in rats trained to discriminate between TRK-820 (40 μg/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 κ-opioid receptor agonists possess U-50,488H-like discriminative stimulus effects. Furthermore, that U-50,488H and the other κ-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.