Brain research bulletin
-
Brain research bulletin · Nov 2012
Increases of theta-low gamma coupling in rat medial prefrontal cortex during working memory task.
Cross-frequency coupling (CFC) between the theta (4-12Hz) phase and the amplitude of gamma (30-100Hz) oscillations occurs frequently in brain. However, the function of theta-gamma coupling in rat medial prefrontal cortex (mPFC) in working memory remains unclear. To address this issue, we studied 16-channel CFC in local field potentials (LFPs) recorded from the mPFC of over-trained rats as they performed a Y-maze working memory task. ⋯ Meanwhile, more channels showed higher theta-low gamma coupling levels during the correct performance. By contrast, the strength of theta-high gamma coupling did not significantly increase during the working memory task in both correct and error trials, indicating an insignificant correlation with the performance validity. These findings suggest a role of mPFC theta-low gamma coupling in working memory.
-
Brain research bulletin · Nov 2012
The role of the dopamine D2 receptor in descending control of pain induced by motor cortex stimulation in the neuropathic rat.
We studied in rats with a spinal nerve ligation-induced neuropathy whether dopamine D2 receptors (D2Rs) play a role in descending control of pain induced by stimulation of the primary motor cortex (M1). Noxious heat-evoked responses were determined in spinal dorsal horn wide-dynamic range (WDR) and nociceptive-specific (NS) neurons, with and without electrical M1 stimulation. A D2R antagonist, raclopride, was administered into the dorsal striatum or spinally in attempts to reverse spinal antinociception induced by M1 stimulation. ⋯ After blocking the A11 with lidocaine or spinal D2Rs with raclopride, M1 stimulation failed to suppress the noxious heat-evoked withdrawal reflex. The results indicate that descending pain control induced by stimulation of the M1 cortex in neuropathic animals involves supraspinal (presumably striatal) and, through A11, spinal D2Rs. Supraspinal and spinal D2Rs have partly dissociative effects on spinal dorsal horn WDR and NS neurons, possibly reflecting differential roles and wirings that these sensory neurons have in pain-processing circuitries.