Anterior cingulate cortex contributes to the descending facilitatory modulation of pain via dorsal reticular nucleus.
Supraspinal centres biphasically modulate spinal nociceptive transmission, including descending inhibition and facilitation. Recent studies have revealed that descending facilitatory modulation is a key mechanism underlying induction and maintenance of neuropathic and inflammatory pain. The anterior cingulate cortex (ACC) is not only involved in the transmission of pain sensation but also plays a role in processing pain-related emotion. The ACC also widely connects with relevant regions of the descending modulation system. Here we used electrophysiological and behavioural techniques to study the possible pathways behind the modulation of spinal nociceptive transmission from the ACC. C-fibre-evoked field potentials in the spinal dorsal horn were produced by electrical stimulation of the sciatic nerve at an intensity high enough to excite C fibres, and paw withdrawal latencies (PWLs) to noxious heating were recorded. The results showed that high-frequency tetanic electrical stimulation of the ACC both unilaterally enhanced the C-fibre-evoked field potentials in the spinal dorsal horn and bilaterally shortened PWLs, indicating a facilitation of spinal nociception. A similar effect was observed after microinjection of N-methyl-d-aspartic acid (NMDA; 10 nm, 1 microL) or homocysteic acid (HCA; 0.1 m, 1 microL) into the ACC. When the dorsal reticular nucleus (DRt) was electrolytically lesioned, ACC-induced facilitation of spinal nociception was blocked. These results imply that: (i) activation of the ACC may facilitate spinal nociception; (ii) NMDA receptors in the ACC may be involved in descending facilitation; and (iii) the DRt plays a crucial role in mediating ACC-induced facilitation of spinal nociception.
Zhang
Ling
L
Institute of Neurobiology, Fudan University, Shanghai 200433, P R China.
Zhang
Yuqiu
Y
Zhao
Zhi-Qi
ZQ
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D005071:Evoked Potentials / Q000502:physiology / Q000528:radiation effects; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D007839:Functional Laterality; D006179:Gyrus Cinguli / Q000503:physiopathology*; D006710:Homocysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D008845:Microinjections / Q000379:methods; D016202:N-Methylaspartate / Q000494:pharmacology; D009413:Nerve Fibers, Myelinated / Q000502:physiology / Q000528:radiation effects; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology / Q000528:radiation effects; D009434:Neural Pathways / Q000503:physiopathology*; D009619:Nociceptors / Q000503:physiopathology*; D010146:Pain / Q000473:pathology / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods; D020671:Posterior Horn Cells / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012154:Reticular Formation / Q000503:physiopathology* / Q000528:radiation effects; D013997:Time Factors
D018690:Excitatory Amino Acid Agonists; D006710:Homocysteine; C007956:homocysteic acid; D016202:N-Methylaspartate