The effects of intranigral injections of picrotoxin and carbachol in cats with a lesioned nigrostriatal pathway.

Picrotoxin, carbachol and atropine were injected intranigrally through chronically implanted crannulae in cats. The drug-induced behavioural syndromes, mainly asymmetric behaviour, were analyzed. The changes in these syndromes after 6-hydroxydopamine (6-OHDA) lesion of the substantia nigra (SN) indicate that, in addition to the dopaminergic (DA), a non-catecholaminergic (non-CA) nigral output exists, both being responsible for asymmetric behaviour. It is further suggested that gamma-aminobutyric acid (GABA) receptors are present on both dopaminergic and non-CA nigral output neurons, while acetylcholine (ACh) receptors, responsible for asymmetric behaviour, are almost exclusively located on non-CA nigral output neurons.