Dopamine and NMDA systems modulate long-term nociception in the rat anterior cingulate cortex.
The anterior cingulate cortex (ACC) plays a key role in pain processing. It has been reported that increased activity of glutamatergic projections into the ACC intensifies nociception; whereas dopaminergic projections inhibit it. The aim of this study was to evaluate the role of dopaminergic and NMDA systems of the ACC in the modulation of long-term nociception elicited by sciatic denervation in the rat. Score, onset and incidence of long-term nociception were measured by the autotomy behavior. The effects of a single microinjection into the ACC of different doses of dopamine (100 nM, 100 microM and 100 mM), a NMDA receptor antagonist (MK801 200 nM and 9.34 mM) and amantadine, a dopamine agonist and NMDA receptor antagonist (10, 100 and 1000 microM) were tested on long-term nociception. Dopamine diminished autotomy behavior in an inverse dose-dependent manner, with dopamine 100 nM as most effective concentration. MK801 and amantadine elicited a significant reduction on autotomy score. Prior injections of D1 and D2 receptor antagonists blocked the antinociceptive effects of amantadine on long-term nociceptive behavior. The present study suggests an interaction between dopaminergic and glutamatergic systems within the ACC in the genesis and maintenance of long-term nociception.
Laboratorio de Neurofisiología Integrativa, Subdirección de Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente, Camino a Xochimilco, 101 San Lorenzo Huipulco Tlalpan, México DF cp 14370, Mexico.
Alberto
A
López-Avila
Ulises
U
Coffeen
J Manuel
JM
Ortega-Legaspi
Rosendo
R
del Angel
Francisco
F
Pellicer
D000547:Amantadine / Q000494:pharmacology; D000818:Animals; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology / Q000502:physiology*; D015259:Dopamine Agents / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006179:Gyrus Cinguli / Q000502:physiology*; D008297:Male; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000502:physiology*
D015259:Dopamine Agents; D065127:Dopamine D2 Receptor Antagonists; D018691:Excitatory Amino Acid Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate; D000547:Amantadine; D004298:Dopamine