Rapid behavioural and biochemical effects of tetanus toxin microinjected into the substantia nigra: a dual role for GABA?

Tetanus toxin (200--250 mouse lethal doses) microinjected unilaterally into the substantia nigra produced rapid behavioural and biochemical effects. If the toxin was injected into the rostral part of the substantia nigra (SN), contralateral turning was observed. Raised ipsilateral striatal levels of the dopamine (DA) metabolite, homovanillic acid (HVA), indicated that this turning was due to activation of the nigro-striatal dopamine system. Caudal nigral injections of tetanus toxin produced ipsilateral turning. Biochemical estimations suggest that this behaviour change was mediated by a non-dopamine (non-DA) pathway.