Postmortem evidence of structural brain changes in schizophrenia. Differences in brain weight, temporal horn area, and parahippocampal gyrus compared with affective disorder

Dopamine receptors and the dopamine hypothesis of schizophrenia

The discovery of neuroleptic drugs in 1952 provided a new strategy for seeking a biological basis of schizophrenia. This entailed a search for a primary site of neuroleptic action. The Parkinsonian effects caused by neuroleptics suggested that dopamine transmission may be disrupted by these drugs. In 1963 it was proposed that neuroleptics blocked "monoamine receptors" or impeded the release of monoamine metabolites. The neuroleptic concentration in plasma water or cerebrospinal fluid was of the order of 2 nM for haloperidol in clinical therapy. A systematic research was made between 1963 and 1974 for a primary site of neuroleptic action which would be sensitive to 2 nM haloperidol and stereoselective for (+)-butaclamol. Direct evidence that neuroleptics selectively blocked dopamine receptors occurred in 1974 with the finding that nanomolar concentrations of these drugs stereoselectively inhibited the binding of [3H]-dopamine or [3H]-haloperidol. These binding sites, now termed D2 dopamine receptors (which inhibit adenylate cyclase), are blocked by neuroleptics in direct relation to the antipsychotic potencies of the neuroleptics. No such correlation exists for D1 receptors (which stimulate adenylate cyclase). Based on the fact that dopamine-mimetic drugs elicited hallucinations, and that neuroleptics caused rigidity, Van Rossum in 1966 had suggested a hypothesis that dopamine pathways may be overactive in schizophrenia. The D2-selective blockade by all neuroleptics (except the monoamine-depleting reserpine) provided strong support for the dopamine hypothesis. Further support now comes from postmortem data and in vivo positron tomographic data, both of which indicate that the density of D2 receptors are elevated in the schizophrenic brain. The postmortem data indicate a bimodal pattern with half the schizophrenics having striatal D2 densities of 14 pmol/g (control is 13 pmol/g) and the other half having 26 pmol/g. Current positron tomographic data indicate D2 densities of 14 pmol/g in control subjects, but values of 34 pmol/g in drug-naive schizophrenics. Future tests of the dopamine hypothesis of schizophrenia may entail an examination of the amino acid composition and genes for D2 receptors in schizophrenic tissue, an examination of the ability of the D2 receptor to become phosphorylated and to desensitize into the low-affinity state, and an examination of the interaction of D2 receptors with D1 receptors or other neurotransmitters.

Computed tomography in affective disorders. Part I. Ventricular and sulcal measurements

Sixty patients with affective illness were examined by computed tomography (CT) and compared to 60 age- and sex-matched controls. Using three different methods of measurement, no differences in ventricular brain ratio (VBR) between patients and controls could be detected. However, linear ventricular values of the frontal horns plus the bicaudate distance (Huckmann number) and the third ventricle were enlarged in the total group of patients. This was also found in subgroups of older, male, psychotic, unipolar, Dexamethasone Suppression Test (DST) positive, and lithium-treated patients when compared to individually matched controls. Younger, nonpsychotic, female, bipolar, DST-normal and non-lithium-treated patients did not differ from controls. The Huckmann number correlated with the duration of illness, as measured by the first episode and the number of episodes. The comparison between the subgroups of patients yielded higher linear and VBR values in older subjects, in men, and in psychotic subjects, whereas no differences were found in comparisons between unipolar versus bipolar, DST-positive versus DST-negative, and lithium-treated versus non-lithium-treated patients.

Obstetric complications, neurodevelopmental deviance, and risk of schizophrenia

It is concluded from a review of the literature and a pilot survey that schizophrenic patients more frequently have a history of obstetric complications (OCs) than do other psychiatric patients and normal subjects. OCs are associated with increased cerebral ventricular size in both infancy and adulthood, and are more common among non-familial schizophrenic patients. Neonatal cerebrovascular events consequent upon OCs provide a mechanism to explain the increased risk of neurodevelopmental deviance and later schizophrenia.

Cell loss in the hippocampus of schizophrenics

To investigate whether volume reduction of the hippocampal formation of schizophrenics, as described previously, is paralleled by loss of neurons and fibre systems, tissue volumes and cell numbers of all parts of the hippocampal formation in post mortem brains of 13 schizophrenics and 11 age-matched controls belonging to the Vogt collection were determined. Volumes of the whole hippocampal formation (P less than 0.01), the whole pyramidal band (P less than 0.001) and the hippocampal segments CA1/CA2 (P less than 0.01), CA3 (P less than 0.005), CA4 (P less than 0.01) were decreased, whereas no significant volume reduction of the alveus and fimbria hippocampi and prosubiculum/subiculum could be found. The perforant path showed a trend towards volume reduction (P less than 0.1). The absolute number of pyramidal cells (tissue volume X cell density) was diminished in CA1/CA2 (P less than 0.05), CA3 (P less than 0.05) and CA4 (P less than 0.05), but was not significantly changed in the prosubiculum/subiculum, the presubiculum/parasubiculum and the granular cell layer of the dentate fascia. Pyramidal cell loss in CA1/CA2, CA3, CA4 was more distinct in the paranoid patients than in catatonics. The findings are discussed with respect to current hypotheses of limbic dysfunction in schizophrenia.

The continuum of psychosis and its implication for the structure of the gene

Three observations challenge Kraepelin's binary view of the functional psychoses: a bimodal distribution of the clinical features of manic-depressive illness and schizophrenia has not been demonstrated; affective illness appears to predispose to schizophrenia in later generations; and 'schizoaffective' illnesses cannot be separated in family studies from either of the prototypical psychoses. The alternative concept is that psychosis is a continuum extending from unipolar, through bipolar affective illness and schizoaffective psychosis, to typical schizophrenia, with increasing degrees of defect. According to this concept the genes predisposing to psychosis have a degree of stability that ensures that the form of the psychosis tends to remain the same within families, but there is also the possibility of change, implying that the genetic mechanisms themselves are variable. It is proposed that quantal changes in the 'virogene' are due to replications within the genome (e.g. the generation of tandem repeats of the element or a component of it); that such replications occur at a critical stage (e.g. gametogenesis, fertilisation, very early embryogenesis) in the course of reproduction; and that the 'season of birth effect' reflects the operation of the mechanism responsible for these replications.

Gliosis in schizophrenia: a survey

Increased gliosis has been previously described in schizophrenic brain. In this study, the degree of gliosis in schizophrenic and control brains was assessed quantitatively using an antibody to glial fibrillary acidic protein, immunocytochemical techniques, and a computed image analysis system. Twenty separate brain areas were assessed, and no significant differences were found between the schizophrenic and control groups. It seems unlikely that a specific pattern of pathologically significant gliosis is present in schizophrenic brains. These negative findings are of note because of previously reported structural differences in the temporal lobe in the schizophrenic group in this series.