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Central nervous system (CNS) demyelination represents the pathological hallmark of multiple sclerosis (MS) and contributes to other neurological conditions. Quantitative and specific imaging of demyelination would thus provide critical clinical insight. Here, we investigated the possibility of targeting axonal potassium channels to image demyelination by positron emission tomography (PET). These channels, which normally reside beneath the myelin sheath, become exposed upon demyelination and are the target of the MS drug, 4-aminopyridine (4-AP). We demonstrate using autoradiography that 4-AP has higher binding in non-myelinated and demyelinated versus well-myelinated CNS regions, and describe a fluorine-containing derivative, 3-F-4-AP, that has similar pharmacological properties and can be labeled with 18F for PET imaging. Additionally, we demonstrate that [18F]3-F-4-AP can be used to detect demyelination in rodents by PET. Further evaluation in Rhesus macaques shows higher binding in non-myelinated versus myelinated areas and excellent properties for brain imaging. Together, these data indicate that [18F]3-F-4-AP may be a valuable PET tracer for detecting CNS demyelination noninvasively.

Disrupted sensory processing, characterized by over-or underresponsiveness to environmental stimuli, has been reported in children with a variety of developmental disabilities. This study examined the effects of prenatal stress and moderate-level prenatal alcohol exposure on tactile sensitivity and its relationship to striatal dopamine system function in thirty-eight 5-to 7-year-old rhesus monkeys. The monkeys were from four experimental conditions: (a) prenatal alcohol exposed, (b) prenatal stress, (c) prenatal alcohol exposed + prenatal stress, and (d) sucrose controls. Increased D 2 receptor binding in the striatum, evaluated using positron emission tomography neuroimaging, was related to increased withdrawal (aversion) responses to repetitive tactile stimuli and reduced habituation across trials. Moreover, prenatal stress significantly increased overall withdrawal responses to repetitive tactile stimulation compared to no prenatal stress.Sensory processing disorders, characterized by under-or overresponsiveness to sensory stimulation that most individuals perceive as harmless (Ayres & Robbins, 1979) NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript estimated to occur in 5% of the general population (Ahn, Miller, Milberger, & McIntosh, 2004) and seem to pose a unique challenge for people with developmental disabilities (Baranek, 2002), including autism, attention deficit hyperactivity disorder (ADHD), fragile X syndrome, and other developmental disabilities (Ayres & Tickle, 1980;Baranek, 1999;Baranek & Berkson, 1994;Baranek, Foster, & Berkson, 1997;Cermak & Daunhauer, 1997;Grandin, 1992;Kinnealey, 1973;Larson, 1982;Mangeot et al., 2001;Miller et al., 1999). Understanding the neurobiological processes associated with sensory processing disruptions is important to developing appropriate preventative and intervention approaches.This study examined whether disrupted sensory processing occurs in monkeys as a result of prenatal exposure to alcohol and/or stress, and if so, whether it would be associated with dopamine functioning in the striatum assessed with positron emission tomography (PET) neuroimaging. We employed a primate model for these studies because in human studies causal conclusions are difficult to reach due to confounding variables. Even with the best statistical analyses it is difficult, if not impossible, to separate completely the effects of variables associated with alcohol use, such as psychological stress, tobacco use, or chaotic home life, from the effects of fetal alcohol exposure per se. Nonhuman primates also have the advantage of gestation characteristics and early development similar to the human, and their shorter life span makes longitudinal studies somewhat easier to conduct. Rhesus monkeys were used because of the large amount of available data on their behavior and development in laboratory settings (Harlow & Harlow, 1969;Suomi, 1997) A. Jean Ayres (1964), an occupational therapist and educational psychologist, coined the term "tactile defensiveness" t...

Neither L-DOPA nor its radiolabeled analog fluoroDOPA is metabolized or accumulates specifically in dopaminergic or even catecholaminergic neurons. Substantial dopamine production within serotonin and norepinephrine neurons may play a role in either therapeutic effects or adverse effects of therapy with L-DOPA.