| Popis: |
The effects of intracerebroventricular injection (10 μl) of μ- and δ-selective opioid peptides on behaviors induced by the dopamine D 2 -selective agonist RU 24213 were investigated in the mouse, using multi-dimensional behavioral analyses. Fifteen to 30 min after the start of behavioral measurements, a 3.0 mg/kg dose of RU 24213 produced a marked increase in linear locomotion, circling, rearing and grooming behaviors. Although the μ-selective opioid peptide lD-Ala 2 ,NMePhe 4 ,Gly-ol 5 ]enkephalin (DAGO) (0.003 and 0.01 μg) itself did not significantly affect behaviors, DAGO (0.01 μg) antagonized the RU 24213 (3.0 mg/kg)-induced increase in behaviors such as linear locomotion, circling, rearing and grooming. Additionally, the effects of DAGO on RU 24213-induced behaviors were fully reversed by treatment with the μ-selective alkylating agent β-funaltrexamine (β-FNA) (5.0 μg). In contrast, the δ-selective opioid peptide [D-Pen 2 ,L-Pen 5 ]enkephalin (0.3 or 1.0 μg) had no marked effects on RU 24213 (3.0 mg/kg)-induced behaviors. These results suggest that μ- but not S-opioid receptors play an inhibitory role in the behaviors induced by the selective activation of dopamine D 2 receptors. |
