Investigation of the pruritus-induced functional activity in the rat brain using manganese-enhanced MRI

Purpose To provide clear information on the activation regions of itching, we investigated the functional activity of cerebral regions in the pruritus‐induced rat model using manganese‐enhanced magnetic resonance imaging (MEMRI). Materials and Methods Itching was induced via neonatal capsaicin treatment in Sprague‐Dawley rats (itching rats), and scratching behavior of the control, itching, and gabapentin (GBP)‐treated itching rats was compared. Then the activated or deactivated brain regions were investigated in the control, itching, and GBP‐treated itching rats using a 4.7T MRI system. Results While the itching rats engaged in vigorous scratching (121.2 ± 22.4 times), the scratching behavior was decreased in the GBP‐treated itching rats (30.6 ± 8.8 times). GBP induced the attenuation of functional activity in two regions −7.10 mm from bregma, in one region −6.65 mm from bregma, and in one region −6.06 mm from bregma. The brain regions related to itching were as follows: parafascicular nucleus, thalamus, superior/inferior colliculus, periaqueductal gray, cingulate cortex, amygdala, midbrain regions, lateral habenula, and hypothalamic areas. Conclusion Our MEMRI investigation indicates new functional activity of cerebral regions in rats due to the effect of itching or GBP. This information could be used to monitor the therapeutic effects of novel agents or for clinical strategies to treat pathological itch. J. Magn. Reson. Imaging 2015;42:709–716.