New Insights About Chemical Transmission in the Brain

Abstract

Twenty years ago neuropharmacology was still in its infancy. The number of neurotransmitters identified in the central nervous system was limited essentially to the monoamines. The spark unleashing the development of this discipline came from studies in Sweden which charted for the first time the existence of discrete monoaminergic neuronal pathways in the brain. The analysis of central catecholamine (noradrenaline and dopamine) metabolism was just beginning, allowing the investigation of the mechanisms of action of various psychotropic drugs whose effects on behavior had been identified in psychiatry several years earlier. Compared with the sophisticated and elegant methods available to electrophysiologists, the experimental techniques of neurochemistry were very crude. Biochemical studies were restricted essentially to the understanding of presynaptic events, since techniques were not available to study the postsynaptic, receptor-mediated aspects of neurotransmitter function. This approach, however, was vindicated by the discovery of a degeneration of nigrostriatal dopaminergic neurones in Parkinson’s disease, and by encouraging results concerning antidepressant and neuroleptic drug action: it was envisaged that depression might result from a dysfunction of central noradrenergic neurones, whilst a hyperactivity of dopaminergic transmission in the limbic system might underly part of the symptomatology of schizophrenia.