True SIA should be accompanied by decreased immediate-early gene expression in the pain-processing neurons of the spinal cord dorsal horn; we observed a dramatic (≥50%) decrease in Fos protein–positive neurons in mice injected with zymosan and exposed to male but not female experimenters or shirts (Kruskal-Wallis test statistic: 12.0, degrees of freedom = 4, P < 0.05; Fig. 2d). Much is known about the neurochemistry of SIA, which exists in opioid (naloxone-reversible9), non-opioid (cannabinoid-1 (CB1) receptor–mediated10) and mixed opioid/non-opioid11 forms. The male experimenter SIA seen here was found to be the latter, as it was blocked (observer × drug interaction: F3,56 = 2.8, P < 0.05) by the broad-spectrum opioid receptor antagonist naloxone (1 mg per kg body weight (mg/kg); P < 0.05), by the inverse CB1 receptor agonist AM-251 (10 mg/kg; P < 0.05) and by a combination of the two drugs (P < 0.01), at doses not affecting pain sensitivity per se (Fig. 2e).
In other words, pain in mice is associated with a particular protein binding neurons in a particular part of the brain. The researchers showed that in mice handled by men, the proportion of those neurons bound by the pain-associated protein was significantly decreased, supporting the hypothesis that male-handled mice are actually experiencing less pain.
Comments
It's properly addressed in the actual paper [0]:
True SIA should be accompanied by decreased immediate-early gene expression in the pain-processing neurons of the spinal cord dorsal horn; we observed a dramatic (≥50%) decrease in Fos protein–positive neurons in mice injected with zymosan and exposed to male but not female experimenters or shirts (Kruskal-Wallis test statistic: 12.0, degrees of freedom = 4, P < 0.05; Fig. 2d). Much is known about the neurochemistry of SIA, which exists in opioid (naloxone-reversible9), non-opioid (cannabinoid-1 (CB1) receptor–mediated10) and mixed opioid/non-opioid11 forms. The male experimenter SIA seen here was found to be the latter, as it was blocked (observer × drug interaction: F3,56 = 2.8, P < 0.05) by the broad-spectrum opioid receptor antagonist naloxone (1 mg per kg body weight (mg/kg); P < 0.05), by the inverse CB1 receptor agonist AM-251 (10 mg/kg; P < 0.05) and by a combination of the two drugs (P < 0.01), at doses not affecting pain sensitivity per se (Fig. 2e).
In other words, pain in mice is associated with a particular protein binding neurons in a particular part of the brain. The researchers showed that in mice handled by men, the proportion of those neurons bound by the pain-associated protein was significantly decreased, supporting the hypothesis that male-handled mice are actually experiencing less pain.
http://www.nature.com/nmeth/journal/vaop/ncurrent/full/nmeth...