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Biomedical subjects

J F Deakin

Publications and source records attributed to J F Deakin.

101 records · Page 6Linked to original sources
PubMed1977

The nucleus accumbens--possible site of antipsychotic action of neuroleptic drugs?

The hypothesis that neuroleptic drugs exert their therapeutic effects by blocking dopaminergic transmission has been investigated by examining the effects of 3 neuroleptic drugs on dopamine turnover in 2 dopaminergically innervated regions of brain--the neostriatum and nucleus accumbens. The drugs chlorpromazine, thioridazine and fluphenazine, known to be therapeutically active in the treatment of schizophrenia, but to have differing incidences of extrapyramidal side effects, were administered to rats in dose ratios approximating to those effective in man. All 3 drugs induced a similar rise in the content of the dopamine metabolite homovanillic acid (HVA) in the nucleus accumbens, whilst the changes in HVA observed in the neostriatum were in the rank order in which these drugs produce extrapyramidal side effects. While the concentrations of dopamine metabolites in the frontal cortex were too low to assess the possibility that neuroleptic drugs have actions at this level, our results are consistent with the hypothesis that these drugs exert their therapeutic effects by dopamine receptor blockade in the nucleus accumbens.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1976

Dopamine and schizophrenia.

The antipsychotic actions and extra-pyramidal side-effects of neuroleptic drugs are strongly correlated with their ability to block central dopaminergic transmission. It is argued that the former are more closely related to actions on dopaminergic mechanisms in the "mesolimbic dopamine" system, and the latter to similar actions in the striatum. Although the amphetamine psychosis closely resembles paranoid schizophrenia and may be due to excess dopamine release, clinical, biochemical, and endocrine studies suggest that dopaminergic overactivity is not a necessary concomitant of schizophrenic illnesses. It is suggested that the primary defect in schizophrenia does not lie in the dopamine neuron. It remains to be excluded that the receptors, particularly in the mesolimbic dopamine areas, become supersensitive, or that there is a deficit in a system which normally acts in antiagonism to the to the mesolimbic dopamine system.

Animals↗
PubMedDate not supplied

A two-process theory of schizophrenia: evidence from studies in post-mortem brain.

Glutamate and GABA are the principle neurotransmitters of the cerebral cortex and are known to modulate dopaminergic function. Evidence of structural abnormalities in the cortex raises the possibility that schizophrenia involves disturbances of cortical amino-acid neurotransmission. The psychotomimetic effects of phencyclidine, a glutamate antagonist, have been taken to suggest that schizophrenia involves reduced brain glutamate function. Direct evidence for diminished glutamate function in schizophrenia is lacking. However, in polar temporal cortex and hippocampus we reported evidence of an asymmetric loss of glutamate terminals, and of reduced GABA function, which may be secondary to the loss of glutamatergic input. Glutamate cell body markers are spared in temporal lobe; the neurones which degenerate may originate in frontal cortex. A number of studies have reported increases in markers of glutamatergic cell bodies and terminals in orbital frontal cortex in schizophrenia. These findings are consistent with the presence of an abnormally abundant glutamatergic innervation, which may be the result of an arrest in the normal process of cellular and synaptic elimination which occurs during development. There is evidence that frontal abnormalities in schizophrenia are genetically determined. We suggest that glutamatergic abnormalities in anterior temporal cortex in schizophrenia are the result of the degeneration of fronto-temporal projections. Orbital frontal projections to polar temporal cortex may be prone to degeneration because they arise from an unstable frontal cortical cytoarchitecture which has not completed the normal process of post-natal remodelling. The structural abnormality of the orbital frontal region may confer vulnerability to some intrinsic or extrinsic mechanism, which brings about a progressive degeneration of projections to polar temporal lobe.

Brain↗
PubMedDate not supplied

The Northwick Park electroconvulsive therapy trial.

70 patients with endogenous depression, defined by strict criteria, who fulfilled the Newcastle indications for electroconvulsive therapy (ECT) were randomly allocated either to a course of eight simulated ECTs or to a course of eight real ECTs. The improvement in terms of psychiatrists' ratings in the group of patients given real ECT was significantly greater (p < 0.01) than that in those given simulated ECT, but the difference between the two groups was small in relation to the considerable improvement of both groups over the 4-week treatment period. No differences were found between the two groups at one-month and six-month follow-up. The therapeutic benefits of electrically induced convulsions in depression were of lesser magnitude and were more transient than has sometimes been claimed. In the real-ECT group memory was impaired during treatment but memory tests revealed no difference between the groups at six-month follow-up.

Adult↗