Walid Abi-Saab

Delta-9-tetrahydrocannabinol effects in schizophrenia: Implications for cognition, psychosis, and addiction

BACKGROUND Recent advances in the neurobiology of cannabinoids have renewed interest in the association between cannabis and psychotic disorders. METHODS In a 3-day, double-blind, randomized, placebo-controlled study, the behavioral, cognitive, motor, and endocrine effects of 0 mg, 2.5 mg, and 5 mg intravenous Delta-9-tetrahydrocannabinol (Delta-9-THC) were characterized in 13 stable, antipsychotic-treated schizophrenia patients. These data were compared with effects in healthy subjects reported elsewhere. RESULTS Delta-9-tetrahydrocannabinol transiently increased 1) learning and recall deficits; 2) positive, negative, and general schizophrenia symptoms; 3) perceptual alterations; 4) akathisia, rigidity, and dyskinesia; 5) deficits in vigilance; and 6) plasma prolactin and cortisol. Schizophrenia patients were more vulnerable to Delta-9-THC effects on recall relative to control subjects. There were no serious short- or long-term adverse events associated with study participation. CONCLUSIONS Delta-9-tetrahydrocannabinol is associated with transient exacerbation in core psychotic and cognitive deficits in schizophrenia. These data do not provide a reason to explain why schizophrenia patients use or misuse cannabis. Furthermore, Delta-9-THC might differentially affect schizophrenia patients relative to control subjects. Finally, the enhanced sensitivity to the cognitive effects of Delta-9-THC warrants further study into whether brain cannabinoid receptor dysfunction contributes to the pathophysiology of the cognitive deficits associated with schizophrenia.

Extracellular metabolites in the cortex and hippocampus of epileptic patients

Interictal brain energy metabolism and glutamate–glutamine cycling are impaired in epilepsy and may contribute to seizure generation. We used the zero‐flow microdialysis method to measure the extracellular levels of glutamate, glutamine, and the major energy substrates glucose and lactate in the epileptogenic and the nonepileptogenic cortex and hippocampus of 38 awake epileptic patients during the interictal period. Depth electrodes attached to microdialysis probes were used to identify the epileptogenic and the nonepileptogenic sites. The epileptogenic hippocampus had surprisingly high basal glutamate levels, low glutamine/glutamate ratio, high lactate levels, and indication for poor glucose utilization. The epileptogenic cortex had only marginally increased glutamate levels. We propose that interictal energetic deficiency in the epileptogenic hippocampus could contribute to impaired glutamate reuptake and glutamate–glutamine cycling, resulting in persistently increased extracellular glutamate, glial and neuronal toxicity, increased lactate production together with poor lactate and glucose utilization, and ultimately worsening energy metabolism. Our data suggest that a different neurometabolic process underlies the neocortical epilepsies. Ann Neurol 2005;57:226–235

Striking Differences in Glucose and Lactate Levels between Brain Extracellular Fluid and Plasma in Conscious Human Subjects: Effects of Hyperglycemia and Hypoglycemia

Brain levels of glucose and lactate in the extracellular fluid (ECF), which reflects the environment to which neurons are exposed, have never been studied in humans under conditions of varying glycemia. The authors used intracerebral microdialysis in conscious human subjects undergoing electro-physiologic evaluation for medically intractable epilepsy and measured ECF levels of glucose and lactate under basal conditions and during a hyperglycemia–hypoglycemia clamp study. Only measurements from nonepileptogenic areas were included. Under basal conditions, the authors found the metabolic milieu in the brain to be strikingly different from that in the circulation. In contrast to plasma, lactate levels in brain ECF were threefold higher than glucose. Results from complementary studies in rats were consistent with the human data. During the hyperglycemia–hypoglycemia clamp study the relationship between plasma and brain ECF levels of glucose remained similar, but changes in brain ECF glucose lagged approximately 30 minutes behind changes in plasma. The data demonstrate that the brain is exposed to substantially lower levels of glucose and higher levels of lactate than those in plasma; moreover, the brain appears to be a site of significant anaerobic glycolysis, raising the possibility that glucose-derived lactate is an important fuel for the brain.

AFQ056 treatment of levodopa‐induced dyskinesias: Results of 2 randomized controlled trials

Study objectives were to assess the efficacy, safety, and tolerability of AFQ056 in Parkinsons disease patients with levodopa‐induced dyskinesia. Two randomized, double‐blind, placebo‐controlled, parallel‐group, in‐patient studies for Parkinsons disease patients with moderate to severe levodopa‐induced dyskinesia (study 1) and severe levodopa‐induced dyskinesia (study 2) on stable dopaminergic therapy were performed. Patients received 25–150 mg AFQ056 or placebo twice daily for 16 days (both studies). Study 2 included a 4‐day down‐titration. Primary outcomes were the Lang‐Fahn Activities of Daily Living Dyskinesia Scale (study 1), the modified Abnormal Involuntary Movement Scale (study 2), and the Unified Parkinsons Disease Rating Scale–part III (both studies). Secondary outcomes included the Unified Parkinsons Disease Rating Scale–part IV items 32–33. The primary analysis was change from baseline to day 16 on all outcomes. Treatment differences were assessed. Fifteen patients were randomized to AFQ056 and 16 to placebo in study 1; 14 patients were randomized to each group in study 2. AFQ056‐treated patients showed significant improvements in dyskinesias on day 16 versus placebo (eg, Lang‐Fahn Activities of Daily Living Dyskinesia Scale, P = .021 [study 1]; modified Abnormal Involuntary Movement Scale, P = .032 [study 2]). No significant changes were seen from baseline on day 16 on the Unified Parkinsons Disease Rating Scale‐part III in either study. Adverse events were reported in both studies, including dizziness. Serious adverse events (most commonly worsening of dyskinesias, apparently associated with stopping treatment) were reported by 4 AFQ056‐treated patients in study 1, and 3 patients (2 AFQ056‐treated patient and 1 in the placebo group) in study 2. AFQ056 showed a clinically relevant and significant antidyskinetic effect without changing the antiparkinsonian effects of dopaminergic therapy.

5-HT2 receptor regulation of extracellular GABA levels in the prefrontal cortex.

Monoamines, including both dopamine and serotonin, synapse onto prefrontal cortical interneurons. Dopamine has been shown to activate these GABAergic interneurons, but there are no direct data on the effects of serotonin on GABA release in the prefrontal cortex. We, therefore, examined the effects of the 5-HT2a/c agonist 1-(2,5-dimethoxy-4-iodophenyl-2-aminopropane (DOI) on extracellular GABA levels in the prefrontal cortex of the rat. Local infusions of DOI dose-dependently increased cortical extracellular GABA levels. In addition, systemic DOI administration resulted in Fos protein expression in glutamic acid decarboxylase67-immunoreactive interneurons of the prefrontal cortex. These data indicate that serotonin, operating through a 5-HT2 receptor, acutely activates GABAergic interneurons in the prefrontal cortex. These data further suggest that there may be convergent regulation of interneurons by dopamine and serotonin in the prefrontal cortex.

A double-blind, randomized, placebo-controlled trial of divalproex extended-release in the treatment of bipolar disorder in children and adolescents.

OBJECTIVE To compare the efficacy and safety of divalproex extended-release (ER) to placebo in a 28-day double-blind study of bipolar disorder in children and adolescents and evaluate the safety of divalproex ER in a 6-month open-label extension study. METHOD In the double-blind study, 150 patients (manic or mixed episode, aged 10-17 years) with baseline Young Mania Rating Scale (YMRS) score of 20 or higher were randomized to once-daily placebo or divalproex ER, which was titrated to clinical response or serum valproate concentration of 80 to 125 microg/mL. Sixty-six patients enrolled in the extension study. RESULTS In the double-blind study, a treatment effect was not observed with divalproex ER based on change in mean YMRS score (divalproex ER -8.8 [n = 74]; placebo -7.9 [n = 70]) or secondary measures. Divalproex was similar to placebo based on incidence of adverse events. Four subjects treated with divalproex ER and three treated with placebo discontinued because of adverse events. Mean ammonia levels increased in the divalproex ER group, but only one patient was symptomatic. In the long-term study, YMRS scores decreased modestly (2.2 points from baseline). The most common adverse events were headache and vomiting. CONCLUSIONS The results of the study do not provide support for the use of divalproex ER in the treatment of youths with bipolar I disorder, mixed or manic state. Further controlled trials are required to confirm or refute the findings from this study.

Decreased hippocampal volume on MRI is associated with increased extracellular glutamate in epilepsy patients

Purpose: Temporal lobe epilepsy (TLE) is associated with smaller hippocampal volume and with elevated extracellular (EC) glutamate levels. We investigated the relationship between the hippocampal volume and glutamate in refractory TLE patients.

Blockade of [11C](+)-PHNO binding in human subjects by the dopamine D3 receptor antagonist ABT-925

Dopamine D3 receptors are preferentially localized in the limbic system and midbrain, and thus may be involved in the pathophysiology of neuropsychiatry disorders. [11C](+)-PHNO is the first preferential D3 receptor radioligand in humans, yet there are no blockade studies with a D3 receptor antagonist in humans. This study characterized the blockade of [11C](+)-PHNO binding by ABT-925, a D3 receptor antagonist, in healthy male subjects. Sixteen subjects underwent 2-3 positron emission tomography (PET) scans, at baseline and following one or two doses of ABT-925 ranging from 50 mg to 600 mg. Receptor occupancies were estimated for globus pallidus, substantia nigra, caudate, putamen, and ventral striatum. At the 600-mg dose (n=9), ABT-925 receptor occupancy (mean+/-s.d.) was higher in substantia nigra (75+/-10%) and globus pallidus (64+/-22%) than in ventral striatum (44+/-17%), caudate (40+/-18%) and putamen (38+/-17%) (ANOVA: F4,140=15.02, p<0.001). The fractions of [11C](+)-PHNO binding attributable to D3 receptors in D3 receptor-rich regions were 100% (substantia nigra) and 90% (globus pallidus), and in D2 receptor-rich regions were 55% (caudate) and 53% (putamen). The ED50 of ABT-925 was 4.37 microg/ml across regions. Our results demonstrate that [11C](+)-PHNO binding can be blocked by a D3 receptor antagonist and confirm preclinical findings that [11C](+)-PHNO signal in the substantia nigra and globus pallidus is mainly reflective of its binding to D3 receptors. Thus, [11C](+)-PHNO seems a suitable PET radiotracer to estimate D3 receptor occupancy in humans.

Divalproex ER Combined with Olanzapine or Risperidone for Treatment of Acute Exacerbations of Schizophrenia

The objective of this study was to evaluate the efficacy and safety of divalproex sodium extended release (divalproex ER) vs placebo in combination with olanzapine or risperidone for the treatment of acute exacerbations of schizophrenia. In this 12-week, randomized, double-blind, parallel-group, multi-center trial, a total of 402 patients were randomized and treated; 103 received olanzapine/placebo, 99 received olanzapine/divalproex ER, 101 received risperidone/placebo, and 99 received risperidone/divalproex ER. Divalproex ER was initiated on day 1 at 20 mg/kg per day q AM and was titrated to clinical effect on days 3, 7, and 10, not to exceed a maximum dosage of 35 mg/kg per day. Olanzapine and risperidone were initiated at 5 and 2 mg/day q PM, respectively, increased to 10 and 4 mg/day on day 3, and increased to fixed target doses of 15 and 6 mg/day on day 6. No significant treatment difference was demonstrated between the combination therapy and antipsychotic monotherapy groups on the primary efficacy variable of the mean change from baseline to day 14 last observation carried forward on the Positive and Negative Syndrome Scale (PANSS) total score, although antipsychotic monotherapy did demonstrate superiority to combination therapy on the PANSS Negative subscale at several time points. Combination therapy also failed to show an advantage over antipsychotic monotherapy at day 84 on the PANSS total score. Most adverse events observed in the study were mild to moderate in severity, and the overall number of adverse events did not differ significantly between the combination therapy groups and their corresponding antipsychotic monotherapy group.

Divalproex Extended-Release in Adolescent Migraine Prophylaxis: Results of a Randomized, Double-Blind, Placebo-Controlled Study

Objective.— To evaluate the efficacy, tolerability, and safety of 3 different doses of divalproex sodium extended‐release vs placebo in the prophylaxis of migraine headaches in adolescents.