Adrienne C. Lahti - US grants

schizophrenia; psychiatric patient care; patient care management; health science research; training; biomedical facility; behavioral /social science research tag; human subject; clinical research;

DESCRIPTION (adapted from applicant's abstract): Antipsychotic drugs reduce psychosis, induce motor effects, and have miscellaneous other actions. The brain substrates of these effects, beyond actions on receptor populations are poorly understood. The investigator proposes to determine the dynamic time course of the effects of antipsychotics on regional cerebral blood flow (rCBF) using PET and 15OH2 in drug-free schizophrenia patients as a direct pharmacodynamic assessment of drug action in the human brain. rCBF measurements would span the pharmacokinetic time course. The investigator proposes to characterize the dynamic time course of rCBF alterations following the acute and six days of administration of two different antipsychotic drugs, the traditional antipsychotic haloperidol and the newer antipsychotic olanzapine. The ability of the changes in rCBF following acute and subacute antipsychotic administration to predict subsequent treatment response would also be evaluated. Based on their preliminary findings, the investigators hypothesize that acute and subacute drug-induced rCBF changes in selected regions will predict treatment response for positive symptoms (anterior cingulate and medial frontal cortex), for negative symptoms (middle frontal cortex and inferior parietal cortex), and motor side effects (basal ganglia). The proposed subacute drug administration regimen would approximate a pharmacokinetic steady state for both antipsychotics. An additional aim of the proposal is to compare the rCBF changes induced by haloperidol versus olanzapine during the scanning sessions obtained with acute and subacute (steady state) antipsychotic administration. The investigator proposes that the pattern of activation in the basal ganglia will best discriminate the two antipsychotic agents. These studies will hopefully provide rCBF correlates of antipsychotic activity. This information will allow the development of hypotheses related to drug mechanism of action, as well as potential surrogate markers of drug action.

human therapy evaluation; schizophrenia; antipsychotic agents; piperidine; sign /symptom; pharmacokinetics; drug screening /evaluation; chemosensitizing agent; delusions; clozapine; neuropharmacology; haloperidol; cognition disorders; dopamine antagonists; hallucinations; clinical research; human subject;

human therapy evaluation; schizophrenia; behavior test; antipsychotic agents; haloperidol; drug screening /evaluation; brain circulation; brain electrical activity; drug administration rate /duration; behavioral /social science research tag; positron emission tomography; human subject; clinical research;

PROJECT SUMMARY/ABSTRACT The goal of the proposal is to perform experiments encompassing human brain imaging and human postmortem studies aimed at identifying neuronal markers of treatment response to antipsychotic medication (APD). Our imaging studies have made significant progress by revealing that limbic neuronal networks are related to psychosis and treatment response to APD. In drug-free patients we found psychotic symptoms to be related to rCBF patterns in the anterior cingulate cortex (ACC) and the hippocampus (HIP). APD-induced functional changes in ventral striatum (VS) and HIP observed after one week of treatment are predictive of treatment response. Our postmortem studies of the striatum indicate that patients who responded to treatment had more dopaminergic (DA) synapses, suggesting that elevated striatal DA relates to treatment response. In addition, the number of glutamate (GLU) synapses was significantly different between treatment good (GR) and poor (PR) responders, suggesting that GLU transmission is affected differentially. The results of these studies informed our hypothesis that in GR, DA receptor blockade in VS restores GLU transmission that was inhibited through elevated DA. Consequently, there is greater GLU activity in VS and GLU-mediated projections to limbic regions, such as the ACC and HIP, leading to restored neuronal integrity. We have hypothesized that the early physiological processes that lead to therapeutic benefit with APD are related to changes in GLU transmission within the VS and in GLU-mediated projections to limbic regions and that treatment response in good and poor responders is characterized by differential pattern of alterations affecting the integrity and function of neuronal synapses. We will test this hypothesis using complementary imaging and postmortem yielding data that will permit the formulation of a comprehensive model for APD responses in subjects with severe mental illness. We will seek to replicate and extend our PET findings with fMRI using tasks that are known to activate the HIP (Episodic memory task) and the ACC (Stroop task). This aim will further seek to parse out the differential contribution of the HIP and ACC to treatment response. At the same time, N-acetylaspartate (NAA), a marker of neuronal integrity and GLU measurements obtained with proton magnetic resonance spectroscopy (1H-MRS) will directly probe in the living brain the relation between neuronal integrity, GLU-function and treatment response. In parallel, the postmortem work will concentrate on the ACC, as this region shows the most reliable imaging data. We will attempt to determine the mechanism by which changes in NAA and GLU are made by examining input and output layers of the ACC in GR and PR. We will quantify morphological indicies of neuronal integrity in glutamte neurons, count the number and structural integrity of mitochondria in GLU neurons and count the number and size of glutamatergic synapses.These studies should allow the development of hypotheses about the pathophysiology of treatment response and provide a basis for the interpretation of functional imaging data. The overarching goal is to identify imaging markers that will predict treatment response, and to confirm or validate these biomarkers using anatomical studies of postmortem tissue. Early detection of drug response would yield specific treatment strategies that are tailored to the individual, thus improving both the quality of life of the patients and drastically reducing the costs associated with unsuccessful treatments strategies.

DESCRIPTION (provided by applicant): The prodromal phase and the early stages of the schizophrenia illness are associated with significant decreases in social and intellectual abilitie, with more modest declines seen with chronic disease. Meta-analyses have consistently identified a relationship between the longer duration of untreated psychosis (DUP), the duration between the onset of positive symptoms and treatment, and worse long term outcomes. However, the neurobiology of this phenomenon and its implications for response to antipsychotic medications remain poorly understood. Glutamatergic excess altering brain connectivity might provide an explanation for why those with longer DUP have worse clinical outcomes. We propose to use multimodal neuroimaging to study 67 first episode psychosis subjects before and after sixteen weeks of treatment with risperidone, a commonly prescribed antipsychotic. We will measure indices of (1) glutamate and (2) structural and functional brain connectivity and test the hypotheses that glutamatergic abnormalities are present in first episode patients and that longer DUP is associated with greater functional and structural connectivity abnormalities that set the stage for poor response to treatment. Our previous combined MR spectroscopy (1H-MRS), diffusion tensor imaging (DTI), and resting state functional MR (fMRI) studies have made progress in the understanding of abnormalities in the glutamate system and brain connectivity in unmedicated patients with schizophrenia and modulation of these by antipsychotic medication. We have identified two indices of glutamatergic dysfunction, elevated glutamate and a disturbance in the known correlation between N-acetyl-aspartate and glutamate, which is suggestive of glutamate/glutamine cycle abnormalities. While antipsychotic medications appear to modulate glutamate, the disturbance in the correlation between metabolites is not restored with treatment. In addition, we found that both structural and functional connectivity abnormalities in unmedicated patients with schizophrenia predict patients' subsequent response to treatment. To our knowledge, no other group has performed a study that uses a combination of complementary neuroimaging techniques that will allow generating a broad characterization of glutamatergic function and brain connectivity in first episode psychosis and their change with treatment. The results of proposed studies could suggest a mechanism by which DUP is associated with poor treatment response which might lead to new interventions to target DUP.

ABSTRACT Schizophrenia is a heterogeneous disorder that likely involves multiple underlying pathological mechanisms, which has plagued attempts to identify rational therapeutic targets. All available antipsychotic drugs (APD) are dopamine receptor antagonists, but clinical response is variable, with a third of patients being partial responders, and a third non-responders. Arguably, those who respond well to APD have primarily dopaminergic abnormalities but it is imperative to also characterize the specific underlying pathologies in those with poor response in order to unravel the heterogeneity of psychosis and effectively develop new treatments. We propose to longitudinally follow treatment response to APD for eight months in medication-naïve first episode psychosis (FEP) subjects using complementary brain imaging techniques. We already have identified provisional markers for several different pathophysiological mechanisms underlying psychosis, including abnormalities in glutamate, brain connectivity, and neurodevelopment that we can track with brain imaging. In addition, we propose to study the changes that occur in the brain in early compared to delayed treatment responders and changes that occur over time in response to treatment. By characterizing treatment trajectories and their relationship to baseline pathophysiologic alterations, we will further complement our mechanistic understanding of the heterogeneity of psychosis. We propose to study 60 well-characterized FEP subjects who are medication naïve and treat them with the most frequently used APD for 32 weeks. We will follow a rigorous longitudinal design to capture treatment response whereby those without an adequate response after 16 weeks of treatment will be switched to another APD for 16 weeks. All patients will be scanned four times: at baseline and after 6, 16, and 32 weeks of treatment. We will use (1) proton MR Spectroscopy (MRS), (2) task and resting state functional MRI and (3) MRI and diffusion weighted imaging (DWI) to measure brain biochemistry, function and structure. Using several imaging modalities has the potential to interrogate different neurobiological aspects of treatment response and will offer greater opportunities for clustering the patterns and combinations of the underlying pathologies in those with poor response. Deconstructing the heterogeneity of psychosis has broad implications for the identification of specific targets for drug development, and to lay the groundwork needed to conduct therapeutic trials on patients characterized by their specific underlying psychopathology.