[D-Arg]Kyotorphin-induced ipsilateral rotation: evidence for in vivo effects independent of Met-enkephalin release.

Kyotorphin (Tyr-Arg) and its stable analogue [D-Arg]kyotorphin were injected into the substantia nigra of rats. Intranigral [D-Arg]-kyotorphin resulted in consistent ipsilateral rotational behavior which was naloxone-reversible. In comparison, intranigral Met-enkephalin induces naloxone-sensitive contralateral rotation. These results indicate a pharmacological effect of [D-Arg]kyotorphin in the substantia nigra that would appear to be independent of Met-enkephalin release.