Abstract

COFFEEN, Ulises et al. Central processing of neuropathic pain: an integrative approach. Salud Ment [online]. 2012, vol.35, n.5, pp.367-374. ISSN 0185-3325.

The term pain matrix refers to the structures and pathways in the central nervous system that play a role in pain processing and integration. For the last several years, our group has been studying the mechanisms that are involved in the establishment of long-term pain. Our research focus has been the study of the different nuclei and corticolimbic pathways that are involved in the affective-cognitive component of pain. In addition, we have also explored painful processes and memory. The pain matrix is constituted by the ventral tegmental area (VTA), anterior cingulate cortex (ACC), and insular cortex, among others. VTA is a predominantly dopaminergic area and has projections to ACC and the insular cortex. Stimulation of this region can reduce nociception, whereas its lesion has the opposite effect. In the ACC, it has been studied how excitatory aminoacids, such as glutamate, increase nociception while inhibitory ones decrease it. Moreover, this cortex is associated with mechanisms of pain memory. In this sense, we have seen that blocking cholinergic receptors diminishes the acquisition of pain-related memories. Nociceptive stimuli increase the expression of inhibitory muscarinic M2 receptors. In relation with insular cortex, the focus of study has been on the dopaminergic system. We have found that blocking dopaminergic D₂ receptors significantly reduces neuropathic nociception. In response to an inflammatory process there is a decrease in the extracellular levels of dopamine and in the expression of mRNA for excitatory dopamine D₁ receptors, while there is an increase in mRNA expression for inhibitory D₂ receptors. Despite current progress in this research area, more studies are needed in order to integrate the relationship among the different neurotransmission systems. This will contribute to the proposal of novel therapeutic alternatives to the conventional treatments for pain.

Keywords : Pain; nociception; insular cortex; anterior cingulate cortex; ventral tegmental area.

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