Dynorphin A(1–13) modulates apomorphine-induced behaviors using multidimensional behavioral analyses in the mouse

Abstract

The effects of intracerebroventricular injection of dynorphin A(1–13) on apomorphine-induced behavioral changes were investigated in the mouse using multidimensional behavioral analyses based upon a capacitance system. Although lower doses (0.1 or 0.3 mg/kg) of apomorphine were without marked effects on behaviors, a 0.56 mg/kg dose of the drug evoked a significant increase in rearing behaviors. Furthermore, 1.0 and 3.0 mg/kg doses of apomorphine produced a marked increment in linear locomotion, circling and rearing. Dynorphin A(1–13) (3.0 or 10.0 μg) itself had no effects on behaviors. The apomorphine (0.56 and 1.0 mg/kg)-induced increase in rearing behaviors was clearly inhibited by treatment with dynorphin A(1–13) (3.0 and 10.0 μg). Simultaneously, the marked increases in linear locomotion and circling were displayed by apomorphine (1.0 mg/kg) plus dynorphin A(1–13) (10.0 μg). The effects of dynorphin A(1–13) (10.0 μg) on the apomorphine (1.0 mg/kg)-induced increase in rearing were entirely reversed by the opioid antagonist Mr2266. These results suggest that the antagonistic effects of dynorphin A(1–13) on the apomorphine (1.0 mg/kg)-induced increase in rearing are mediated via opioid receptors, possibly κ-sites.