Decreased glutamic acid decarboxylase67 messenger RNA expression in a subset of prefrontal cortical gamma-aminobutyric acid neurons in subjects with schizophrenia.

BACKGROUND: Markers of gamma-aminobutyric acid (GABA) neurotransmission seem to be altered in the prefrontal cortex (PFC) of subjects with schizophrenia. We sought to determine whether the expression of the messenger RNA (mRNA) for the synthesizing enzyme of GABA, glutamic acid decarboxylase67 (GAD67), is decreased in the PFC of subjects with schizophrenia, whether this change is present in all or only some GABA neurons, and whether long-term treatment with haloperidol decanoate contributes to altered GAD67 mRNA expression. METHODS: Tissue sections from 10 pairs of subjects with schizophrenia and control subjects and 4 pairs of haloperidol-treated and control monkeys were processed for in situ hybridization histochemical analysis with sulfur-35-labeled oligonucleotide probes for GAD67 mRNA and exposed to nuclear emulsion. Within each layer of PFC area 9, neurons expressing a detectable level of GAD67 mRNA were quantified for cell density and the relative level of mRNA expression per cell (grain density per neuron). RESULTS: In subjects with schizophrenia, the density of labeled neurons was significantly (P<.05) decreased by 25% to 35% in cortical layers 3 to 5. In contrast, the mean grain density per labeled neuron did not differ across subject groups. Similar analyses in monkeys revealed no effect of long-term haloperidol treatment on either the density of the labeled neurons or the grain density per labeled neuron. CONCLUSIONS: These findings indicate that in subjects with schizophrenia, GAD67 mRNA expression is relatively unaltered in most PFC GABA neurons but is reduced below a detectable level in a subset of GABA neurons. Altered GABA neurotransmission in this subset may contribute to PFC dysfunction in subjects with schizophrenia.

Decreased somal size of deep layer 3 pyramidal neurons in the prefrontal cortex of subjects with schizophrenia.

BACKGROUND: Schizophrenia is associated with deficits in working memory, a cognitive function that depends on the connections of the prefrontal cortex (PFC) with the thalamus and other cortical regions. Pyramidal neurons in PFC deep layer 3 play a central role in both thalamocortical and corticocortical circuitry. Given that somal size tends to be associated with both the dendritic and axonal architecture of a neuron, abnormalities in these circuits in schizophrenia may be associated with a change in the somal size of deep layer 3 pyramidal neurons. METHODS: We used design-based stereology to estimate the somal volume of pyramidal neurons in deep layer 3 of PFC area 9 in 28 subjects with schizophrenia, each of whom was matched to 1 normal comparison subject for sex, age, and postmortem interval. RESULTS: The geometric mean of the somal volume estimates in the subjects with schizophrenia was significantly (P =.02) decreased by 9.2%. This decrease was associated with a shift in the distribution of somal volumes toward smaller sizes. Neither antipsychotic medication treatment history nor duration of illness was associated with somal size. CONCLUSIONS: These findings independently replicate previous reports of decreased somal size in the PFC in schizophrenia. The reduction in size of deep layer 3 pyramidal neurons is consistent with abnormalities in thalamocortical and corticocortical circuitry, suggesting that disruption of these circuits may contribute to cognitive abnormalities in schizophrenia.

Frontostriatal measurement in treatment-naive children with obsessive-compulsive disorder.

BACKGROUND: Abnormalities in frontostriatal circuits have been implicated in obsessive-compulsive disorder (OCD). Although OCD commonly emerges during childhood or adolescence, few studies have examined frontostriatal anatomy in psychotropic-naive children with OCD near the onset of illness to determine the possible role of atypical developmental processes in this disorder. METHODS: Magnetic resonance imaging scans from 19 children with OCD who had not been exposed to psychotropic drugs, aged 7 to 18 years, and 19 case-matched healthy control subjects were analyzed to determine the volumes of the following structures: prefrontal cortex, striatum (caudate and putamen), lateral and third ventricles, and intracranial volume. RESULTS: Patients with OCD had significantly smaller striatal volumes and significantly larger third ventricle volumes than controls, but did not differ in prefrontal cortical, lateral ventricular, or intracranial volumes. Striatal volumes were inversely correlated with OCD symptom severity but not illness duration. CONCLUSIONS: Our findings provide new evidence of abnormalities of the striatum in pediatric OCD. These results are preliminary, given the small sample size.

Decreased density of tyrosine hydroxylase-immunoreactive axons in the entorhinal cortex of schizophrenic subjects.

BACKGROUND: We recently reported a laminar-specific reduction in the density of tyrosine hydroxylase (TH)-immunoreactive axons in the prefrontal cortex of subjects with schizophrenia. In this report, we extend these investigations to the entorhinal cortex (ERC), another candidate site of dysfunction in this disorder. METHODS: Using immunocytochemical techniques and blind quantitative analyses, we determined the density of TH-immunoreactive axons in the rostral subdivision of the ERC from seven matched pairs of schizophrenic and control subjects. RESULTS: The relative density of TH-labeled axons was significantly decreased by over 60% in layers 3 and 6, but not in layer 1, of the ERC in schizophrenic subjects. In contrast, in the prefrontal cortex of the same subjects, labeled axon density was significantly decreased by 62% only in layer 6. Furthermore, the length of TH-labeled axons did not differ between six matched pairs of nonschizophrenic psychiatric and control subjects in any layer of the ERC. Finally, the density of TH-labeled axons in the ERC of cynomolgus monkeys chronically treated with haloperidol was not reduced relative to control animals. CONCLUSIONS: These findings reveal regional- and laminar-specific alterations in TH-immunoreactive axons that appear to be specific to the pathophysiology of schizophrenia.

Altered GABA neurotransmission and prefrontal cortical dysfunction in schizophrenia.

Dysfunction of the dorsolateral prefrontal cortex appears to be a central feature of the pathophysiology of schizophrenia, and this dysfunction may be related to alterations in gamma aminobutyric acid (GABA) neurotransmission. Determining the causes and consequences of altered GABA neurotransmission in schizophrenia, and the relationship of these changes to other abnormalities in prefrontal cortical circuitry, requires an understanding of which of the multiple subpopulations of cortical GABA neurons are affected. The chandelier class of GABA neurons, especially those located in the middle layers of the prefrontal cortex (PFC), have been hypothesized to be preferentially involved in schizophrenia because they 1) receive direct synaptic input from dopamine axons, 2) exert powerful inhibitory control over the excitatory output of layer 3 pyramidal neurons, and 3) undergo substantial developmental changes during late adolescence, the typical age of onset of schizophrenia. Consistent with this hypothesis, the axon terminals of chandelier neurons, as revealed by immunoreactivity for the GABA membrane transporter, are reduced substantially in the middle layers of the PFC in schizophrenic subjects. This alteration appears to be selective for the chandelier class of GABA neurons and for the disease process of schizophrenia. These findings provide insight into the pathophysiologic mechanisms underlying prefrontal cortical dysfunction in schizophrenia, and they reveal new targets for therapeutic intervention in this illness.

Alterations in chandelier neuron axon terminals in the prefrontal cortex of schizophrenic subjects.

OBJECTIVE: Abnormalities in prefrontal cortical gamma-aminobutyric acid (GABA) neurotransmission may contribute to cognitive dysfunction in schizophrenia. The density of chandelier neuron axon terminals (cartridges) immunoreactive for the GABA membrane transporter (GAT-1) has been reported to be reduced in the dorsolateral prefrontal cortex of schizophrenic subjects. Because cartridges regulate the output of pyramidal cells, this study analyzed the laminar distribution of GAT-1-immunoreactive cartridges to determine whether certain subpopulations of pyramidal cells are preferentially affected. METHOD: Measurements were made of the density of GAT-1 -immunoreactive cartridges in layers 2-3a, 3b-4, and 6 of dorsolateral prefrontal cortex area 46 in 30 subjects with schizophrenia, each of whom was matched to one normal and one psychiatric comparison subject. GAT-1-immunoreactive cartridge density was also examined in monkeys chronically treated with haloperidol. RESULTS: Relative to both comparison groups, the schizophrenic subjects had significantly lower GAT-1-immunoreactive cartridge density in layers 2-3a and 3b-4. The decrease was most common and most marked in layers 3b-4, where 80% of the schizophrenic subjects exhibited an average 50.1% decrease in cartridge density in comparison with the matched normal subjects. In contrast, GAT-1-immunoreactive cartridge density was unchanged in the haloperidol-treated monkeys. CONCLUSIONS: These findings demonstrate that the density of GAT-1-immunoreactive cartridges is reduced in the majority of schizophrenic subjects and that this alteration may most prominently affect the function of pyramidal cells located in the middle cortical layers. This abnormality may reflect a number of underlying deficits, including a primary defect in dorsolateral prefrontal cortex circuitry or a secondary response to altered thalamic input to this region.

Lamina-specific deficits in parvalbumin-immunoreactive varicosities in the prefrontal cortex of subjects with schizophrenia: evidence for fewer projections from the thalamus.

OBJECTIVE: Neuronal number in the mediodorsal thalamic nucleus, the principal source of thalamic projections to the prefrontal cortex, has been reported to be lower in subjects with schizophrenia. The authors tested the hypothesis that schizophrenia is associated with a selective deficit in a marker of thalamic axon terminals in the middle layers of the prefrontal cortex, the primary zone of termination of thalamic axons. METHOD: The densities of parvalbumin-immunoreactive varicosities (putative axon terminals) were determined in the superficial and middle layers of prefrontal cortex area 9 from 20 matched pairs of subjects with schizophrenia and normal comparison subjects. In order to determine the specificity of these observations, similar studies were conducted in subjects with major depressive disorder and in monkeys after 9-12 months of haloperidol treatment. RESULTS: The relative densities of parvalbumin-immunoreactive varicosities did not differ between schizophrenic and comparison subjects in the superficial layers. However, in the middle layers, mean varicosity density was significantly lower (24% difference) in the subjects with schizophrenia. In contrast, neither subjects with major depressive disorder nor haloperidol-treated monkeys exhibited a middle-layer density of parvalbumin-immunoreactive varicosities that was lower than that of their matched comparison groups. CONCLUSIONS: Although not definitive, these findings are consistent with the hypothesis of fewer projections from the mediodorsal thalamic nucleus to the prefrontal cortex in schizophrenic subjects and thus converge with other lines of evidence demonstrating an abnormality in thalamo-prefrontal cortical circuitry in persons with schizophrenia.

Lamina-specific alterations in the dopamine innervation of the prefrontal cortex in schizophrenic subjects.

OBJECTIVE: Abnormalities in dopamine neurotransmission in the prefrontal cortex have been implicated in the pathophysiology of schizophrenia. However, the integrity of the dopamine projections to the prefrontal cortex in this disorder has not been directly examined. METHOD: The authors employed immunocytochemical methods and antibodies against tyrosine hydroxylase, the rate-limiting enzyme in dopamine biosynthesis, and the dopamine membrane transporter to examine dopamine axons in the dorsomedial prefrontal cortex (area 9) from 16 pairs of schizophrenic and matched control subjects. RESULTS: Compared to the control subjects, the total length of tyrosine hydroxylase-immunoreactive axons was unchanged in the superficial and middle layers of the schizophrenic subjects but was reduced by an average of 33.6% in layer 6. The total length of tyrosine hydroxylase-positive axons in layer 6 was decreased in 13 of the schizophrenic subjects compared to their control subjects. Axons immunoreactive for the dopamine membrane transporter showed a similar pattern of change. In contrast, axons labeled for the serotonin transporter did not differ between schizophrenic and control subjects in any layer examined. In addition, the density of tyrosine hydroxylase-containing axons did not differ between monkeys chronically treated with haloperidol and matched control animals. CONCLUSIONS: These findings reveal that schizophrenia is associated with an altered dopamine innervation of prefrontal cortex area 9 that is lamina- and neurotransmitter-specific and that does not appear to be a consequence of pharmacological treatment. Together, these data provide direct evidence for a disturbance in dopamine neurotransmission in the prefrontal cortex of schizophrenic subjects.

Inter-rater reliability of the neurological examination in schizophrenia.

Neurological Examination Abnormalities (NEA) are prevalent in schizophrenia, but the significance of this is obscured by methodological problems. The Neurological Evaluation Scale (NES), the most widely used structured neurological examination in schizophrenia research, has had limited study of its inter-rater reliability (IRR). An augmented version of the NES was jointly administered (one examiner-rater and one observer-rater) by three pairs of psychiatrists to two populations of patients with idiopathic psychotic disorders. In addition to the ordinal and categorical data yielded by the original NES, continuous data were recorded in one of the series. Reliability analyses of our populations and a previously published study, reveal consistently adequate IRR in 12 of the 26 items assessed, and inconsistently adequate IRR in an additional 11. Consistent with studies using other NEA schedules, IRR was unacceptably low for some items that rely on subjective severity ratings. Certain rare abnormalities, which posed difficulties for the estimation of IRR, are probably not generally useful in the study of schizophrenia. Reliability estimates of continuous, ordinal and dichotomous data were comparable in most cases. We recommend that certain items from the NES be deleted, and that other studies of NEA in psychiatry follow similar procedures before undertaking further analyses.

Magnetic resonance imaging and spectroscopy in offspring at risk for schizophrenia: preliminary studies.

1. Studies of first-degree relatives of persons with schizophrenia provide an opportunity to characterize risk factors for the development of this illness. In this report the authors will provide preliminary data from an ongoing study of neurobiological alterations in the offspring of schizophrenia patients. 2. A series of offspring of schizophrenic patients (OS) were compared with age and sex matched healthy controls (HC) without psychiatric history in first degree relatives on psychiatric, volumetric Magnetic Resonance Imaging (MRI) of whole brain and proton Magnetic Resonance Spectroscopy (1H MRS) evaluations of the ventral prefrontal cortex. 3. Compared with HC group, high risk subjects had reduced left amygdala volume, enlarged third ventricular volume, and smaller overall brain volume. 4. 1H MRS studies showed a trend for decreased NAA/choline ratios in the anterior cingulate region in the OS group as compared to HC subjects. 5. Follow-up studies of these subjects are needed to confirm the predictive value of these measures for future emergence of schizophrenia in subjects at risk for this illness.