Brain size and cerebral glucose metabolic rate (GMR) were determined with magnetic resonance imaging (MRI) and positron emission tomography (PET) in individuals with mild mental retardation (MR), individuals with Down syndrome (DS) without dementia and in matched controls. The MRI data showed that the MR and the DS groups both had brain volumes of about 80% of controls; variance was greatest within the MR group. PET was obtained with [ 18F]-fluorodeoxyglucose (FDG) as the tracer during a test of attention (Continuous Performance Test; CPT). Whole brain cortex GMR was higher than the controls in both the MR and the DS groups. For all subjects combined, the correlation between brain size and IQ was .65 @ < ,005). Brain imaging with magnetic resonance imaging (MRI) and positron emission tomography (PET) provides an opportunity to characterize brain abnormalities in viva. Structural analyses in severe mental retardation (MR) often reveal brain damage of varying degrees (

Parkinson's disease (PD) involves neuroinflammation, excitotoxicity, mitochondrial dysfunction, and diminished trophic support. The endo-cannabinoid system (comprising small bioactive compounds, their synthetic and catabolic enzymes, their metabotropic and ionotropic receptors, and their transporters) has been implicated in neurophysiology and neurodegeneration, leading to the proposal of medicines derived from Cannabis sativa as new PD therapies. Here, the potential for cannabinoid-based PD therapies is reviewed. The clinical significance of cannabinoids in PD presents both promise and paradox, with varied data emerging from disparate model systems, clinical trials, and delivery modalities, including medical applications of native (plant-derived) and synthetic cannabis products. This picture is complicated further by the multivariate involvement of metabotropic and ionotropic receptors, an emerging understanding of new cannabinoid targets (e.g., PPARγ and GPRs18, 55, and 119), and the potential role of entourage compounds (e.g., geraniol, apigenin) in any protective or therapeutic effects observed.