Abstract
BackgroundExperimental studies suggest that testosterone reduces the nociceptive response after inflammatory and neuropathic stimuli, however the underlying mechanisms have not been fully elucidated. The aims of this study were to evaluate the effect of peripheral blockade of testosterone on pain behaviour and on expression levels of the genes that encode the NaV1.7 and NaV1.8 channels, in dorsal root ganglia in an acute postoperative pain model, as well as the influence of androgen blockade on the expression of these genes.MethodsPostoperative pain was induced by a plantar incision and the study group received flutamide to block testosterone receptor. The animals were submitted to behavioural evaluation preoperatively, 2 h after incision, and on the 1st, 2nd, 3rd and 7th postoperative days. Von Frey test was used to evaluate paw withdrawal threshold after mechanical stimuli and the guarding pain test to assess spontaneous pain. The expression of the genes encoding the sodium channels at the dorsal root ganglia was determined by real time quantitative polymerase chain reaction.ResultsAnimals treated with flutamide presented lower paw withdrawal threshold at the 1st, 2nd, 3rd, and 7th postoperative days. The guarding pain test showed significant decrease in the flutamide group at 2 h and on the 3rd and 7th postoperative days. No difference was detected between the study and control groups for the gene expression.ConclusionsOur data suggest an antinociceptive effect of androgens following plantar incision. The expression of genes that encode voltage-gated sodium channels was not influenced by androgen blockade.
Highlights
Experimental studies suggest that testosterone reduces the nociceptive response after inflammatory and neuropathic stimuli, the underlying mechanisms have not been fully elucidated
Testosterone presented an antinociceptive effect in models of inflammatory pain [7,8,9,10]
To expand the knowledge on the relationship between pain and testosterone, the current study evaluated the effect of peripheral blockade of testosterone on pain behavior and quantified Scn9a and Scn10a expression in dorsal root ganglion (DRG) using a rat model of acute postoperative pain
Summary
Experimental studies suggest that testosterone reduces the nociceptive response after inflammatory and neuropathic stimuli, the underlying mechanisms have not been fully elucidated. The phenomenon of pain receives the influence of several systems in the body, including the limbic, adrenergic, endogenous opioid and hormonal systems. The latter has been receiving more attention in the last 20 years. Testosterone presented an antinociceptive effect in models of inflammatory pain (carrageenan, formalin and Freud’s adjuvant) [7,8,9,10]. The mechanisms underlying such effects of sex hormones, are not fully understood
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