Reduction of Pain Behavior by Stimulation of the Basolateral Amygdalar Nuclei in Freely Moving Rats

Abstract

Low-intensity high-frequency stimulation (HFS) delivered to the basolateral nuclei of the amygdala (BLAs) induced anti-nociceptive effects and reduced spontaneous motor activities in freely moving rats. Stimulation (20 μA, 100 sec–1, 200 μsec square, for 30 sec) was applied through electrodes implanted bilaterally in the BLA. Pain behavioral responses were inhibited by HFS in the formalin test but not in the plantar test. Spontaneous motor activities were also reduced by HFS delivered to the BLAs. Intrathecal injection of naloxone failed to block the analgesic effects of HFS, suggesting the descending opiate system to be minimally involved. We previously reported that HFS delivered to the BLA inhibited nociceptive responses recorded in the prefrontal cortex. Here, we demonstrate that such stimulation under the same conditions also induces analgesic effects in behavior studies.