Pain and itch are closely related sensations, yet qualitatively quite distinct. Despite recent advances in brain imaging techniques, identifying the differences between pain and itch signals in the brain cortex is difficult due to continuous temporal and spatial changes in the signals. The high spatial resolution of positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) has substantially advanced research of pain and itch, but these are uncomfortable because of expensiveness, importability and the limited operation in the shielded room. Here, we used near infrared spectroscopy (NIRS), which has more conventional usability. NIRS can be used to visualize dynamic changes in oxygenated hemoglobin and deoxyhemoglobin concentrations in the capillary networks near activated neural circuits in real-time as well as fMRI. We observed distinct activation patterns in the frontal cortex for acute pain and histamine-induced itch. The prefrontal cortex exhibited a pain-related and itch-related activation pattern of blood flow in each subject. Although it looked as though that activation pattern for pain and itching was different in each subject, further cross correlation analysis of NIRS signals between each channels showed an overall agreement with regard to prefrontal area involvement. As a result, pain-related and itch-related blood flow responses (delayed responses in prefrontal area) were found to be clearly different between pain (τ = +18.7 sec) and itch (τ = +0.63 sec) stimulation. This is the first pilot study to demonstrate the temporal and spatial separation of a pain-induced blood flow and an itch-induced blood flow in human cortex during information processing.
The neuroprotective effects of Hericium erinaceum (H. erinaceum) were studied in mice subjected to middle cerebral artery (MCA) occlusion. Infarct volumes were markedly reduced in mice receiving 14 days of H. erinaceum (300 mg/kg) treatment prior to 4-hr MCA occlusion. Moreover, 14-day pre-ischemic H. erinaceum treatment significantly increased the levels of nerve growth factor (NGF) in both the cortex and striatum of mice subjected to 4-hr MCA occlusion. However, pre-ischemic H. erinaceum treatment had no effect on cerebral blood flow (CBF) in the cortex of mice subjected to MCA occlusion. Treatment with H. erinaceum for 1 day prior to MCA occlusion-induced ischemia had no effect on infarct volume or NGF level. These results suggest that 14 days of treatment with H. erinaceum prior to MCA occlusion protected against focal cerebral ischemia, by increasing NGF levels. This implies that H. erinaceum and its components could be useful for preventing cerebral infarction.
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