| 研究概要 |
The rodent prefrontal cortex (PFC) including cingulate areas is related to the affective dimension of pain. We previously reported PFC nociceptive responses inhibited by inputs from the amygdala. The effects of amygdala was altered by dopamine. We examined direct effects of dopamine (DA) pathways from the ventral segmental area (VTA) on nociceptive responses in PFC.
High frequency stimulation (HFS, 50 Hz, 30 s) delivered to the VTA produced long-lasting suppression (LLS) of nociceptive responses in the rat PFC including cingulate and prelimbic areas. HFS delivered to the VTA, which has been reported to increase DA concentrations in the PFC, significantly suppressed nociceptive responses. The LLS of nociceptive responses persisted for about 30 minutes and recovered to the control level within 60 min after HFS. We also demonstrated local microinjection of a selective D2 agonist of DA receptors to induce LLS of mechanical nociceptive responses.In addition, a D2 antagonist impaired the LLS evoked by HFS. In contrast, DA depletion by a 6-hydroxydopamine injection or a low concentration of DA induced by a κ-opiate receptor agonist injected into the VTA had minimal effect on nociceptive responses in the PFC.
HFS delivered to VTA inhibited nociceptive responses for a long period in PFC. DA D2R activation mediated by local D2 agonist injection also induced LLS of mechanical nociceptive responses. The mesocortical DA system may modify PFC nociceptive responses via D2 activity.
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