Effect of pain related of sex and estrous cycle on blood plasma glucose, free fatty acids and corticosterone in rats

Elzira Diniz De Moraes,Rachel Cezar De Andrade Ribeiro,Angelo Alexander Torres Dos Santos ,Dimas Augusto Morozin Zaia ,Cássia Thaïs Bussamra Vieira Zaia ,Andreia Lopes Da Silva

doi:10.4025/actascibiolsci.v34i4.10568

Elzira Diniz De Moraes, Rachel Cezar De Andrade Ribeiro + Show 4 more

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https://doi.org/10.4025/actascibiolsci.v34i4.10568

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Abstract

Sex differences related with pain have been studied and evidences suggesting influence of sex steroid hormones on the thresholds of pain. Experimental nociception has been test using formalin as a model of nociceptive stimulus. Association of stress, pain and metabolic and hormonal changes has not been explored. The aim of this study was to compare metabolic and hormonal changes between male rats and female rats in proestrus and estrus cycle after painful stimulus by formalin into the masseter muscle. Male and female Wistar rats (200-250 g b.w.) were submitted to an injection of formalin (F, 1.5%) or saline (S, 9.9%) into the masseter muscle and after 0 (N, control group without injection), 5, 15, 30 or 60 minutes they were decapitate and blood was collected to measure biochemical parameters. Plasma estradiol concentration (pg dL -1 ) was significantly higher in proestrus (106.3 ± 4.3, n = 45, p < 0.05) group compared to the estrous group (89.4 ± 3.5, n = 43). Blood plasma concentration of glucose (mg dL -1 ) was increased after 5 and 15 minutes of injection of formalin or saline in the animals, but in the estrus group the increase was bigger than in the others. Free fatty acids levels increased in the estrous group after 5, 15 and 30 minutes and also the corticosterone levels and these concentrations were significantly different (p < 0.05) from either male or female animals in proestrus state. The results obtained suggesting that estradiol is related to a sensibility to pain and the estrus stage is related to stress and the estrous cycle has a modulator effect on pain and nociceptive sensibility.

Highlights

Converging lines of evidence suggest that there are important sex-related influences on the experience of pain
V. 34, n. 4, p. 451-456, Oct.-Dec., 2012 and endogenous pain modulation (BERKLEY, 1997; FILLINGIM; GEAR, 2004). This sex differences may be related to the effect of steroid hormones on the developing and adult nervous systems response to pain (CRAFT et al, 2004; KELLY et al, 2003), and neuromodulatory roles of sex steroid hormones on the opioid system (DAWSONBASOA; GINTZLER, 1998) can be involved
Considering sex-related influences in pain response and the effects elicited by the injection of formalin into deep tissues not yet been explored by metabolic parameters, the aim of this study is to compare metabolic and hormonal changes between males rats and females rats in proestrus and estrus cycle after painful stimulus by formalin into the masseter muscle

Summary

Introduction

Converging lines of evidence suggest that there are important sex-related influences on the experience of pain. Women report more pain than men and they are at great risk for developing many. Laboratory studies consistently report lower pain threshold and tolerance among women and abundant nonhuman animal research indicates sex differences in nociceptive responses. 451-456, Oct.-Dec., 2012 and endogenous pain modulation (BERKLEY, 1997; FILLINGIM; GEAR, 2004). This sex differences may be related to the effect of steroid hormones on the developing and adult nervous systems response to pain (CRAFT et al, 2004; KELLY et al, 2003), and neuromodulatory roles of sex steroid hormones on the opioid system (DAWSONBASOA; GINTZLER, 1998) can be involved.

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