Intranigral injection of dynorphin in combination with substance P on striatal dopamine metabolism in the rat

The effects of intranigral injection of dynorphin(1-13), substance P and their combination on striatal dopamine (DA) metabolism as well as circling behavior were studied in rats. Dynorphin(1-13) produced a significant dose-dependent increase of dihydroxyphenyl acetic acid (DOPAC) concentration as well as the number of contralateral circling. No change in dopamine (DA) concentration was observed. Substance P caused a dose-dependent increase of DOPAC concentration. At large doses it also produced an increase in DA concentration. Combined intranigral dynorphin(1-13) and substance P brought about an additive effect for the increase of DOPAC and the number of contralateral circling. No additive effect was found when dynorphin(1-13) and neurokinin A were injected together intranigrally.