Neurochemistry and Neuroendocrinology of Schizophrenia: A Selective Review

Neurochemical investigation has played a major role in the search for the cause of schizophrenia. Initial research strategies involved the direct measurement of neurochemical substances in biological fluids. Subsequently, indirect measures of brain biochemistry including pituitary hormones and responses to pharmacologic probes were examined. Recent advances in in vivo functional neuroimaging, biochemical neuropathology, and molecular genetics have extended the scope of clinical neurochemical studies. The historical emphasis on the dopamine neurotransmitter system has subsided in the wake of the demonstrated limitations of the dopamine hypothesis of schizophrenia and increased evidence for the role of other neurotransmitters in the pathophysiology of schizophrenia as well as their interactions with dopamine neural systems. The neurotransmitters that have come under increasing scrutiny include serotonin, norepinephrine, glutamate, and related excitatory amino acids, and the neuropeptides cholecystokinin and neurotensin. In this article, the authors reviewed significant recently published neurochemical and neuroendocrine studies of schizophrenia in the context of previous work and found an extensive but fragmentary body of data which provides neither consistent nor conclusive evidence for any specific etiologic theory. Aspects of the disease and methodological limitations that may account for this as well as future research strategies are discussed.