Faculty Bibliography

CX516, a positive modulator of the glutamatergic alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor, improves performance in tasks requiring learning and memory in animals. CX516 was added to clozapine in 4-week, placebo-controlled, dose-finding (N = 6) and fixed-dose (N = 13) trials. CX516 was tolerated well and was associated with moderate to large, between-group effect sizes compared with placebo, representing improvement in measures of attention and memory. These preliminary results suggest that CX516 and other "ampakines" hold promise for the treatment of schizophrenia.

OBJECTIVE: Research has implicated dysfunction of glutamatergic neurotransmission in the pathophysiology of schizophrenia. This review evaluates evidence from preclinical and clinical studies that brain glutamatergic neurotransmission is altered in schizophrenia, may affect symptom expression, and is modulated by antipsychotic drugs. METHOD: A comprehensive review of scientific articles published over the last decade that address the role of glutamate in the pathophysiology of schizophrenia was carried out. RESULTS: Glutamatergic neurons are the major excitatory pathways linking the cortex, limbic system, and thalamus, regions that have been implicated in schizophrenia. Postmortem studies have revealed alterations in pre- and postsynaptic markers for glutamatergic neurons in several brain regions in schizophrenia. The N-methyl-D-aspartic acid (NMDA) subtype of glutamate receptor may be particularly important as blockade of this receptor by the dissociative anesthetics reproduces in normal subjects the symptomatic manifestations of schizophrenia, including negative symptoms and cognitive impairments, and increases dopamine release in the mesolimbic system. Agents that indirectly enhance NMDA receptor function via the glycine modulatory site reduce negative symptoms and variably improve cognitive functioning in schizophrenic subjects receiving typical antipsychotics. CONCLUSIONS: Dysfunction of glutamatergic neurotransmission may play an important role in the pathophysiology of schizophrenia, especially of the negative symptoms and cognitive impairments associated with the disorder, and is a promising target for drug development.

BACKGROUND: Several years ago, we reported that the addition of risperidone to clozapine improved response in some patients with schizophrenia. Risperidone, in general, is well tolerated when administered as monotherapy, but has been linked to a persistent elevation of serum prolactin and associated symptoms. The goal of this study was to determine whether the addition of risperidone to clozapine results in an elevation of serum prolactin levels in patients with chronic schizophrenia or schizoaffective disorder. METHOD: Twenty patients on clozapine-risperidone combination therapy were matched for age and gender with 20 patients treated with clozapine monotherapy. Demographic information was gathered along with clozapine and risperidone dose and the length of time on risperidone. Serum prolactin levels were measured from a single blood sample. RESULTS: The 2 groups did not differ in age, race, gender, diagnosis, age at clozapine initiation, age at onset, Abnormal Involuntary Movement Scale scores, or clozapine dose. The mean +/- SD serum prolactin level was 8.42+/-4.17 ng/mL for clozapine monotherapy patients and 35.76+/-17.43 ng/mL for combination therapy patients. The 2 medication categories showed a significant difference in log prolactin values (t = -7.97, df = 38, p < or = .0001). Sixteen combination therapy patients (80%) exhibited elevated prolactin levels (range for entire group, 9.7-69.8 ng/mL) while only 2 clozapine monotherapy patients (10%) exhibited prolactin elevation levels (range for entire group, 2.4-20.2 ng/mL; df = 1, p < .0001). CONCLUSION: The combination of risperidone and clozapine appears to result in a moderate elevation of serum prolactin levels. Additionally, controlled prospective studies are needed to clarify the risks of long-term elevations of serum prolactin level.

OBJECTIVE: Repeated functional magnetic resonance imaging (fMRI) studies of schizophrenic subjects may identify brain activity changes in response to interventions. To interpret the findings, however, it is crucial to know the test-retest reliability of the measures used. METHOD: The authors scanned seven normal subjects and seven schizophrenic subjects on two occasions during performance of a working memory task. They quantified the reliability of task performance and brain activation. RESULTS: In both groups, task performance was reliable, and all a priori regions were activated in group-averaged test and retest data. In individual schizophrenic subjects, however, indices of cognitive activation were not reliable across sessions. Normal subjects showed reasonable reliability of activation. CONCLUSIONS: Even given reliable task performance, stable clinical status, and a stable pattern of group-averaged activation, individual subjects showed unreliable brain activation. This suggests that repeated fMRI studies of schizophrenia should control for sources of variation, both artifactual and intrinsic.

OBJECTIVE: The authors examined the relationship between treatment with clozapine and rates of arrest of psychotic outpatients with criminal histories. METHOD: Patients who had been given a DSM-IV psychotic diagnosis were selected from an urban outpatient clinic database. Background checks performed on 360 patients identified 165 (45.8%) with positive criminal histories in Massachusetts. The authors reviewed the charts of these patients to determine several variables, including whether and when they had received clozapine. A Poisson regression model was used to regress arrest rates against the variables of age, sex, onset of illness, birth cohort, and clozapine treatment. Risk ratios (i.e., percent change in arrest rates) were then calculated by computing the exponential of the Poisson regression coefficients. RESULTS: The 165 patients included in the analysis had a total of 1,126 arrests. The mean number of arrests was 6.8. Differences were found between the 65 patients who received clozapine and the 100 patients who did not in number of arrests, sex, and onset of illness. The regression revealed significantly higher arrest rate estimates associated with more recent birth cohort (4.8%) and with onset of illness (64.6%) and lower arrest rate estimates associated with higher levels of education (11.6%), receiving clozapine (32.6%), and receiving clozapine during specific periods of time (68.9%). CONCLUSIONS: Clozapine's effect on arrest rates in this group of patients is large enough to warrant further investigation. The data indicate that clozapine may reduce recidivism in subjects with criminal histories who are in need of antipsychotic medication.

BACKGROUND: Working memory (WM) deficits in schizophrenia have been associated with dorsolateral prefrontal cortex (DLPFC) dysfunction in neuroimaging studies. We previously found increased DLPFC activation in schizophrenic versus normal subjects during WM performance (Manoach et al 1999b). We now have investigated whether schizophrenic subjects recruit different brain regions, particularly the basal ganglia and thalamus, components of frontostriatal circuitry thought to mediate WM. METHODS: We examined regional brain activation in nine normal and nine schizophrenic subjects during WM performance using functional magnetic resonance imaging. Subjects performed a modified version of the Sternberg Item Recognition Paradigm that included a monetary reward for correct responses. We compared high and low WM load conditions to each other and to a non-WM baseline condition. We examined activation in both individual subjects and averaged group data. RESULTS: Relative to normal subjects, schizophrenic subjects exhibited deficient WM performance, at least an equal magnitude of right DLPFC activation, significantly greater left DLPFC activation, and increased spatial heterogeneity of DLPFC activation. Furthermore, only the schizophrenic group activated the basal ganglia and thalamus, even when matched for task performance with the normal group. CONCLUSIONS: Aberrant WM performance and brain activation in schizophrenia may reflect dysfunction of frontostriatal circuitry that subserves WM. Future studies will elucidate the contribution of the anatomical components of this circuitry to WM deficits.

OBJECTIVE: The goal of this 5-year naturalistic study of patients treated with clozapine was to examine the incidence of treatment-emergent diabetes mellitus in relation to other factors, including weight gain, lipid abnormalities, age, clozapine dose, and treatment with valproate. METHOD: Data on age, gender, race, diagnosis, family history of diabetes, and age at clozapine initiation were collected from medical records of 82 outpatients with schizophrenia or schizoaffective disorder. Clozapine dose, data on use of valproate, and laboratory test results were recorded at 6-month intervals. RESULTS: The mean age at the time of clozapine initiation of the 82 patients was 36.4 years; 26.8% of the patients were women, and 91.5% were Caucasian. The mean baseline weight was 175.5 lb, and the mean body mass index was 26.9 kg/m(2). Thirty patients (36.6%) were diagnosed with diabetes during the 5-year follow-up. Weight gain, use of valproate, and total daily dose of clozapine were not significant risk factors for developing diabetes mellitus. Patients experienced significant weight gain that continued until approximately month 46 from initiation of clozapine. There was a nonsignificant increase in total serum cholesterol and a significant increase in serum triglycerides level. CONCLUSIONS: The results support the hypotheses that patients treated with clozapine experience significant weight gain and lipid abnormalities and appear to be at increased risk for developing diabetes.

OBJECTIVE: The purpose of this study was to evaluate the effects of high-dose oral glycine on positive and negative symptoms and cognitive function when added to clozapine in adults with schizophrenia. METHOD: The authors conducted a double-blind, placebo-controlled, parallel-group trial of 60 g/day of glycine added to clozapine for 8 weeks in 30 adults with schizophrenia. Clinical ratings were performed every 2 weeks. RESULTS: Twenty-seven patients completed the trial. Glycine augmentation of clozapine produced no statistically significant change in positive or negative symptoms or cognitive functioning. No subjects showed clinically significant worsening of clinical ratings. CONCLUSIONS: These data, combined with data from previous trials with D-cycloserine and glycine, suggest that agonists at the glycine site may be less effective when combined with clozapine than they are when combined with conventional antipsychotics.

Personal risk perceptions of acute myocardial infarction (AMI) affect people's preventive health behaviors as well as their beliefs during a heart attack episode. The authors investigated factors that are associated with personal risk perceptions of having an AMI. A random-digit-dial survey was conducted among 1294 respondents, aged 18 years or older, in 20 communities across the nation as part of the Rapid Early Action for Coronary Treatment (REACT) trial. Results of two mixed-model linear regression analyses suggested that worse perceived general health, more risk factors, and greater knowledge were associated with greater perception of AMI risk. The results also showed that women who answered, incorrectly, that heart disease is not the most common cause of death for women in the United States reported significantly lower risk perceptions than women who answered this question correctly. The findings in this study suggest that interventions need to target specific misconceptions regarding AMI risk.