Calcium-related Neurotoxicity of Cocaine

点击翻译按钮获取中文摘要

DESCRIPTION (provided by applicant): Cocaine-induced stroke and hemorrhage in the brain are among the most serious medical complications. The mechanisms underlying these effects are poorly understood but are likely to reflect in part its vasoactive effects that may be exacerbated with repeated drug exposures. Our poor understanding of the cerebrovascular effects of cocaine are due in part to technological limitations in our ability to concurrently assess and thus distinguish cocaine's neuronal effects from its vascular effects. Here we aim to apply our newly developed optical/ fluorescence imaging techniques (OFIs), to study separately the neuronal and cerebrovascular effects of acute and chronic cocaine exposures. OFIs integrate (1) dual-wavelength laser speckle imaging to enable concurrent detection of cerebral blood flow (CBF), blood volume (CBV), and tissue hemoglobin oxygenation (StO2) at high spatiotemporal resolutions across a large field of view, (2) digital-frequency-ramping Doppler optical coherence tomography for in vivo 3D quantitative imaging of the neurovascular network, (3) Rhod2 fluorescence imaging to measure intracellular calcium ([Ca2+]i), and (4) a micro-catheter probe (mOFI) to assess cocaine's effects on subcortical brain regions in real time and at high spatiotemporal resolution. Our pilot study has shown that acute cocaine decreases CBF while increasing deoxyhemoglobin content and increasing intracellular Ca content and that there is sensitization to these effects with repeated exposures. Since increases in intracellular [Ca2+]i are associated with neuronal death following ischemia, we hypothesize that these sensitized responses with chronic cocaine exposures increase the vulnerability of neuronal tissue to damage from hypoxia. To test these hypotheses, we will use OFIs to concurrently measure the effects of acute and chronic cocaine on cerebrovascular responses (CBF, CBV), tissue oxygenation (StO2) and neuronal [Ca2+]i changes in cortical and subcortical brain regions. We will use an animal model of compulsive cocaine self- administration (short and long access) that mimics key aspects of human addiction. In addition, we will examine the efficacy of calcium channel blockers in preventing cocaine-induced increases in intracellular Ca2+ content, as a potential therapeutic strategy to reduce cocaine's cerebrovascular toxicity. We propose the following Specific Aims: Assess the neuronal and vascular effects of acute and chronic cocaine on cortical (using OFI, Aim 1) and subcortical regions (using mOFI, Aim 2); Characterize the 'ischemia-like' neurovascular dysfunction resulting from chronic cocaine exposure (Aim 3), and examine the efficacy of calcium channel blockers to ameliorate cocaine-induced intracellular [Ca2+]i and hemodynamic changes in brain (Aim 4). The proposed studies will provide a better understanding of the mechanisms that underlie cocaine's cerebrovascular toxicity, which could help develop therapeutic interventions to counteract this toxicity. In addition, the proposed studies will introduce an imaging capability that could be applied to studies of the effects of other drugs of abuse and to studies of other brain disorders for which there are pertinent animal models.