Philip Simkowitz

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Subanesthetic doses of the noncompetitive N-methyl-D-aspartate (NMDA) antagonist ketamine exacerbate psychosis in schizophrenic patients, and ketamine has significant abuse liability. These observations indicate that a secondary effect of ketamine may be to increase dopamine concentrations. The present study was undertaken using positron emission tomography(More)
OBJECTIVE Positron emission tomography and the fluorodeoxyglucose (FDG) method were used to determine the brain's metabolic response to neuroleptic challenge in a normal, disease-free state. METHOD FDG measurements were obtained before and 12 hours after administration of 5 mg of haloperidol to 12 young normal men. These values were compared with(More)
  • S L Dewey, G S Smith, +6 authors A P Wolf
  • Proceedings of the National Academy of Sciences…
  • 1993
Previously we demonstrated that positron emission tomography (PET) can be used to measure changes in the concentrations of synaptic dopamine and acetylcholine. Whether induced directly or indirectly through interactions with other neurotransmitters, these studies support the use of PET for investigating the functional responsiveness of a specific(More)
OBJECTIVE The CNS metabolic response to a neuroleptic challenge in treatment-responsive and nonresponsive schizophrenic patients was measured in order to examine the relation between treatment outcome and the capacity to alter neurochemical function in response to acute receptor blockade. METHOD Positron emission tomography (PET) and(More)
Positron emission tomography and the fluorodeoxyglucose method were used to measure regional brain metabolism before and 2 h after haloperidol (5 mg, i.m.) in 11 young normal men. These data were compared with measures obtained from nine previously studied normal men who had received no drug intervention. Although a previously published study had(More)
OBJECTIVE This study was undertaken to measure serotonergic modulation of dopamine in vivo by using positron emission tomography (PET), a radiotracer for the striatal dopamine D2 receptor ([11C]raclopride), and a pharmacologic challenge of the serotonin system (d,l-fenfluramine). METHOD Two PET studies using [11C]raclopride were performed in 11 normal(More)
Ferritin conjugates of various lectins were used to determine the densities of surface carbohydrates on nerve growth cones produced by different classes of neuron. These neurons, from superior cervical and dorsal root ganglia, spinal cord, olfactory bulb, and cerebellum of the fetal rat, were grown as explant cultures, labeled with the probes, and then(More)
The kinetics of the transport of the 1-anilino-8-naphthalenesulfonate (ANS−, an anionic fluorescent probe of the membrane surface) across phospholipid vesicle membranes have been studied using a stopped-flow rapid kinetic technique. The method has been used to gain detailed information about the mechanism of transport of this probe and to study(More)
The membrane polypeptides of growth cone fragments ("growth cone particles," GCPs) isolated from fetal rat brain by subcellular fractionation have been analyzed in further detail. The major polypeptides of salt-washed GCP membranes detected by 1-dimensional gel electrophoresis (Ellis et al., 1985b) resolve in 2-dimensional gels as a spot of 52 kDa that(More)
Functional brain imaging with positron emission tomography (PET) has opened up new avenues for the investigation of possible functional disturbances related to psychiatric disease as well as pharmacodynamic assessment of drug treatment in vivo. Different strategies to study pharmacologic effects on the brain have been developed in recent years. The basic(More)