Mass fragmentographic assay of gaba in substantia nigra: Effects of agonists and antagonists of dopaminergic and Effects of agonists and antagonists of dopaminergic and cholinergic systems

GABA was measured in rat substantia nigra and cerebellum using a new and simple mass fragmentographic method, allowing for the assay of this neurotransmitter in micrograms of brain tissue samples. Cerebellar GABA levels in animals killed by exposure to focussed microwave irradiations, were significantly higher than those obtained in animals killed by decapitation. 10 minutes after decapitation, however, GABA levels are higher than those in animals sacrificed by microwave irradiations. In order to contribute to the elucidation of the relationship between the dopaminergic, cholinergic and GABAergic systems, GABA levels were measured in substantia nigra of rats treated with drugs interfering with the receptors of dopamine and acetylcholine. Apomorphine, haloperidol, oxotremorine and benztropine fail to induce any change in GABA levels, suggesting either that dopaminergic and cholinergic nerve terminals do not impinge upon GABAergic nerve cells or, more probably, that only turnover studies are an index of GABA functional activity.