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The purpose of this study was to determine if acute nicotine attenuated ketamine-induced regional cerebral blood flow (rCBF). Following 2–4 h of nicotine abstinence, healthy chronic smokers participated in four sets of rCBF studies, HO positron emission tomography, during a simple sensory motor control task. The four drug conditions studied were placebo, ketamine alone, nicotine alone, and ketamine + nicotine. Intravenous ketamine increased rCBF in frontal, orbital–frontal, and anterior cingulate areas. Nicotine alone induced marked rCBF elevations in the lateral occipital cortex and rCBF suppressions in the basal ganglia and anterior cingulate cortex. Nicotine added to ketamine attenuated the ketamine-induced elevated rCBF in the anterior cingulate cortex but caused a marked rCBF increase in the orbital frontal region. This study illustrates the interactive effects of ketamine, an NMDA receptor antagonist, and nicotine in multiple brain regions. Nicotine substantially ameliorated the effects of ketamine on anterior cingulate rCBF and, when given alone, markedly suppressed anterior cingulate rCBF. The enhanced, synergistic orbitofrontal effects observed with ketamine and nicotine together suggest a marked increase in excitatory neurotransmission in a brain region often linked to psychosis, reward, and addictive behaviors. [ABSTRACT FROM AUTHOR]

Up to 80% of patients with schizophrenia experience sleep disturbances, which negatively impact daytime functioning. Given that the glutamatergic system is involved in the pathophysiology of schizophrenia as well as normal sleep-wake neurobiology, the current project aimed to determine whether sleep quality was related to brain glutamate levels in schizophrenia. The Pittsburgh Sleep Quality Index (PSQI) was used to assess subjective sleep quality and proton magnetic resonance spectroscopy (MRS) was used to quantify glutamate in the bilateral anterior cingulate, left parietal cortex, and left hippocampus. Results indicate that global PSQI scores were negatively correlated with the anterior cingulate and parietal glutamate levels. In patients with schizophrenia, poorer sleep quality correlated with greater positive symptom severity. Our findings suggest that poor sleep quality is related to greater positive symptom severity and lower levels of anterior cingulate glutamate in individuals with schizophrenia. Interventions to enhance sleep quality may prove beneficial for patients. Future studies will examine whether glutamate relates to objective measures of sleep quality, and whether glutamate may mediate the relationship between sleep quality and symptom severity across the schizophrenia-spectrum. [ABSTRACT FROM AUTHOR]

In vivo measurement of neurotransmitters and modulators is now feasible with advanced proton magnetic resonance spectroscopy ( 1 H MRS) techniques. This review provides a basic tutorial of MRS, describes the methods available to measure brain glutamate, glutamine, γ-aminobutyric acid, glutathione, N -acetylaspartylglutamate, glycine, and serine at magnetic field strengths of 3 T or higher, and summarizes the neurochemical findings in schizophrenia. Overall, 1 H MRS holds great promise for producing biomarkers that can serve as treatment targets, prediction of disease onset, or illness exacerbation in schizophrenia and other brain diseases. [ABSTRACT FROM AUTHOR]