Brain schizophrenia

For many years it was believed that the brain mechanisms underlying the effects of psychedelic hallucinogens and dissociative anesthetics were separate and distinct. Indeed, there has been considerable debate about which represents the best drag model of schizophrenia. However, recent data show that the two classes of psychotomimetic drags share a common final pathway involving an increase in the release of the excitatory neurotransmitter glutamate. 

Segal DS, Kuczenski R Behavioral alterations induced by an escalating dose-binge pattern of cocaine administration. Behav Brain Res 88 251—260, 1997 Serper MR, Chou JC, Allen MH, et al Symptomatic overlap of cocaine intoxication and acute schizophrenia at emergency presentation. Schizophr Bull 25 387—394, 1999... 

C. The symptoms are not due to a general medical condition (e.g., anatomical lesions and infections of the brain, visual epilepsies) and are not better accounted for by another mental disorder (e.g., delirium, dementia. Schizophrenia) or hypnopompic hallucinations. 

How the different neurotransmitters may be involved in the initiation and maintenance of some brain disorders, such as Parkinson s disease, epilepsy, schizophrenia, depression, anxiety and dementia, as well as in the sensation of pain, is then evaluated and an attempt made to see how the drugs which are used in these conditions produce their effect by modifying appropriate neurotransmitter function (section C). The final section (D) deals with how neurotransmitters are involved in sleep and consciousness and in the social problems of drug use and abuse. 

The localisation of a particular peptide to a particular brain area and possibly associated with a particular transmitter (e.g. CCK with dopamine in mesolimbic pathways) has often prompted a prediction of function (e.g. CCK may have a role in schizophrenia). Animal studies in which the peptide has been injected into the appropriate brain area or tested on slices taken from the brain area have sometimes been taken to confirm such hypotheses. These approaches have lined up the peptides for a whole range of potential roles, some of which are listed in Table 12.4. Whether these predictions are realities will depend on the availability of chemical agents and their evaluation, not only in animals but also in humans. 

Geyer, MA, Swerdlow, NR, Mansbach, RS and Braff, DL (1990) Startle response models of sensorimotor gating and habituation deficits in schizophrenia. Brain Res. Bull. 25 485-498. 

Weinberger, DR (1987) Implications of normal brain development for the pathogenesis of schizophrenia. Arch. Gen. Psychiat. 44 660-669. 

Hornykiewicz, 0. Brain catecholamines in schizophrenia--a good case for noradrenaline. Nature 299 484-486, 1982. 

A diagnosis of schizophrenia is made clinically, as there are no psychological assessments, brain imaging, or laboratory examinations that confirm the diagnosis. 

In the vertebrate CNS monoamines have been associated with a number of physiological functions (reviewed in Kandel et al., 1991). Serotonin has functions associated with mood, pain, sleep, learning, and memory. Dopamine has functions associated with schizophrenia, Parkinson s disease, and cocaine addiction. In vertebrates, dopamine is further metabolized into two additional neurotransmitters, norepinephrine and epinephrine. Norepinephrine increases the excitability of cells in response to sudden sensory input such as fear. Epinephrine has been identified in specific neurons of the brain, but the function of these cells is unknown. In addition, AADC has also been found in a class of neurons that do not have any of the four neurotransmitters discussed above (Jaeger et al., 1983). These neurons may use one of the trace amines, tyramine, tryptamine, or phenylethylamine, as a neurotransmitter. 

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