title: Amygdala-prefrontal pathways and the dopamine system affect nociceptive responses in the prefrontal cortex.
abstract: BACKGROUND
  We previously demonstrated nociceptive discharges to be evoked by mechanical noxious stimulation in the prefrontal cortex (PFC). The nociceptive responses recorded in the PFC are conceivably involved in the affective rather than the sensory-discriminative dimension of pain. The PFC receives dense projection from the limbic system. Monosynaptic projections from the basolateral nucleus of the amygdala (BLA) to the PFC are known to produce long-lasting synaptic plasticity. We examined effects of high frequency stimulation (HFS) delivered to the BLA on nociceptive responses in the rat PFC.
  
  
  RESULTS
  HFS induced long lasting suppression (LLS) of the specific high threshold responses of nociceptive neurons in the PFC. Microinjection of N-methyl-D-aspartic acid (NMDA) receptor antagonists (2-amino-5-phosphonovaleric acid (APV), dizocilpine (MK-801)) and also metabotropic glutamate receptor (mGluR) group antagonists (α-methyl-4-carboxyphenylglycine (MCPG), and 2-[(1S,2S)-2-carboxycyclopropyl]-3-(9H-xanthen-9-yl)-D-alanine (LY341495)), prevented the induction of LLS of nociceptive responses. We also examined modulatory effects of dopamine (DA) on the LLS of nociceptive responses. With depletion of DA in response to 6-hydroxydopamine (6-OHDA) injection into the ipsilateral forebrain bundle, LLS of nociceptive responses was decreased, while nociceptive responses were normally evoked. Antagonists of DA receptor subtypes D2 (sulpiride) and D4 (3-{[4-(4-chlorophenyl) piperazin-1-yl] methyl}-1H-pyrrolo [2, 3-b] pyridine (L-745,870)), microinjected into the PFC, inhibited LLS of nociceptive responses.
  
  
  CONCLUSIONS
  Our results indicate that BLA-PFC pathways inhibited PFC nociceptive cell activities and that the DA system modifies the BLA-PFC regulatory function.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Tokyo Women’s MedicalUniversity Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, 116-8567, Japan.
authors.forename: Kitaro
authors.initials: K
authors.lastname: Onozawa
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yagasaki
authors.forename: Yumi
authors.initials: Y
authors.lastname: Izawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Abe
authors.forename: Yoriko
authors.initials: Y
authors.lastname: Kawakami
mesh_terms: D000679:Amygdala / Q000502:physiology*; D000818:Animals; D004298:Dopamine / Q000172:deficiency / Q000502:physiology*; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D009619:Nociceptors / Q000502:physiology*; D017288:Pain Threshold / Q000502:physiology; D017397:Prefrontal Cortex / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D017557:Ventral Tegmental Area / Q000502:physiology*
chemical_list: D004298:Dopamine
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