Dynamic Processing of Nociception in Cortical Network in Conscious Rats: A Laser-evoked Field Potential Study

Abstract

(1) Field potential study in conscious rats provides a convenient and effective animal model for pain mechanism and pharmacological research. However, the spatial-temporal character of nociception processing in cortex revealed by field potential technique in conscious rats remains unclear. (2) In the present study, multi-channel field potentials evoked by noxious laser stimulation applied to the hind paw of conscious rats were recorded through 12 chronically implanted skull electrodes. Independent component analysis (ICA) was used to remove possible artifacts and to extract the specific nociception-related component. (3) Two fast sharp responses and one slow blunt response were evoked by noxious laser stimulation. Systemic morphine (5 mg/kg, i.p.) preferentially attenuated the amplitude of the slow blunt response while had no significant effect on the first two sharp responses. ICA revealed that those responses came from activities of contralateral anterior parietal area, medial frontal area and posterior parietal area. A movement artifact was also detected in this study. Partial directed coherence (PDC) analysis showed that there were changes of information flows from medial frontal and posterior parietal area to anterior parietal area after noxious laser stimulation. (4) Characterization of the spatio-temporal responses to noxious laser stimulation may be a valuable model for the study of pain mechanisms and for the assessment of analgesia.

Nociceptive Transmission to Rat Primary Somatosensory Cortex – Comparison of Sedative and Analgesic Effects

“…The analgesic effect of Morphine is thought to origin from both spinal and supraspinal mechanisms. The present study shows that LCEP is depressed by systemic Morphine and thus confirms previous data [15], [18], [43]. However, since Morphine also exhibit sedative properties [44]–[45], the possibility that the entire effect on LCEP is due to its sedative properties could not be excluded.…”

丘脑皮层通路神经元的伤害性反应

“…In the first 60 min (phases 1 and 2) of formalin test, the amount of information flow significantly increased from medial to lateral pathway, whereas it decreased from lateral to medial pathway. Subsequent findings by independent component analysis (ICA) of multichannel field potentials in rats [37] and functional connectivity analysis of human fMRI data [38] confirm the hypothesis that a network of brain regions participates in the nociceptive or tactile processing in a functional connective mode.…”

Modulation of Central Nociceptive Coding by Acupoint Stimulation

“…Similarly, in a laser-evoked field potential study in rats, we observed that nociceptive evoked potentials could be separated into several independent components, which represented the activities of anterior and posterior parietal area, medial frontal area, and anterior cingulate cortex, respectively [36]. Partial directed coherence (PDC) and cross-correlation analysis showed that the direction and amount of information flow between cortical areas presented stable and periodical changes after brief noxious laser stimulation.…”

“…Partial directed coherence (PDC) and cross-correlation analysis showed that the direction and amount of information flow between cortical areas presented stable and periodical changes after brief noxious laser stimulation. This suggested that transient noxious stimulation may lead to repeated reciprocal flowing of nociceptive related information within the central neural network [36].…”