Turning behaviour and catalepsy after injection of excitatory amino acids into rat substantia nigra

Unilateral injection of AMPA ((R,S)-α-3-hydroxyl-5-methyl-4-isoxazolepropionic acid), 4-bromohomoibotenic acid, kainic acid and N-methylaspartic acid into the caudal part of substantia nigra induced ipsilateral turning behaviour. AMPA and kainic acid were most potent. Ibotenic acid produced short-lasting ipsilateral turning followed by long-lasting contralateral turning behaviour which was antagonized by the GABA antagonist bicuculline methiodide. The turning induced by AMPA was not blocked by previous 6-hydroxydopamine lesion of the nigrostriatal dopaminergic pathway and was increased by systemic apomorphine. High doses of bilateral intranigral AMPA induced rigid catalepsy. The results are consistent with an involvement of glutamate or aspartate receptors in the regulation of dopamine output systems.