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Papers of the Week


Papers: 21 Dec 2019 - 27 Dec 2019

RESEARCH TYPE:
Psychology


Animal Studies, Pharmacology/Drug Development


2020 04


Behav Pharmacol


31


2&3

Pain and stress: functional evidence that supra-spinal mechanisms involved in pain-induced analgesia mediate stress-induced analgesia.

Authors

Tobaldini G, Andersen EOL, Polato JJ, Guilhen VA, Gaspar JC, Lazzarim MK, Sardi NF, Fischer L
Behav Pharmacol. 2020 04; 31(2&3):159-167.
PMID: 31860563.

Abstract

Analgesia induced by stressful and painful stimuli is an adaptive response during life-threatening situations. There is no evidence linking the mechanisms underlying them, while the former depends on the activation of stress-related brain pathways, the second depends on opioidergic mechanisms in the nucleus accumbens and on nicotinic cholinergic mechanisms in the rostral ventromedial medulla. In this study, we hypothesized that stress-induced analgesia is also dependent on opioidergic mechanisms in the nucleus accumbens and on nicotinic cholinergic mechanisms in the rostral ventromedial medulla. We used immobilization, a classical procedure to induce acute stress, and evaluated its ability to decrease the nociceptive responses induced either by carrageenan or by formalin in rats. Immobilization stress significantly decreased either carrageenan-induced hyperalgesia or formalin-induced tonic nociception in a time-dependent manner. This stress-induced analgesia is similar to pain-induced analgesia, as revealed by contrasting the antinociceptive effect induced by immobilization and by a forepaw injection of capsaicin. The administration of a µ-opioid receptor antagonist (CTOP, 0.5 µg) into the nucleus accumbens, as well as that of a nicotinic cholinergic receptor antagonist (mecamylamine, 0.6 µg) into the rostral ventromedial medulla, blocked immobilization stress-induced analgesia in both pain models. These results demonstrate that supraspinal mechanisms which are known to mediate pain-induced analgesia also mediate stress-induced analgesia. Therefore both forms of analgesia have overlapping mechanisms, probably recruited in response to the perception of danger.