Sex-related differences in descending norepinephrine and serotonin controls of spinal withdrawal reflex during intramuscular saline induced muscle nociception in rats

Effects of simulated weightlessness on intramuscular hypertonic saline induced muscle nociception and spinal Fos expression in rats

“…As mentioned above, we have demonstrated earlier that secondary mechanical hyperalgesia and heat hypoalgesia during the exposure to conditioning muscle nociception are dependent on descending modulations originating in distinct brain regions Lei et al, 2011;You et al, 2010You et al, , 2013You et al, , 2014. It may be proposed that the simulated weightlessness-induced enhancement of descending facilitation and decrease of descending inhibition rather than a general disinhibition of nociceptive neurons in the spinal DH explains the present findings.…”

“…: contralateral) (n ¼6 for each group). You, 2013; Lei et al, 2011;You et al, 2010You et al, , 2013You et al, , 2014. These recent findings are supported by the observation that secondary heat hyperalgesia is rarely reported, while secondary mechanical hyperalgesia is a common finding (Treede et al, 1992;Pertovaara, 1998;Heinricher et al, 2009).…”

“…As described elsewhere (You et al, 2010Lei, et al, 2011), a bolus of 0.2 ml 5.8% hypertonic (HT) saline was injected unilaterally into the gastrocnemius (GS) muscle to establish tonic muscle nociception. The injection site was located at the middle site of the GS muscle, and the depth of the needle insertion into the GS muscle was about 0.5 cm.…”

Differences in carbachol dose, pain condition, and sex following lateral hypothalamic stimulation

“…Antinociception is also significantly greater in male than female rats overall on the tail flick and electric shock-induced jump tests following intrathecal injection of clonidine, an alpha 2 -adrenoceptor agonist (Kiefel and Bodnar, 1991). Additionally, females exhibit long term mechanical hyperalgesia compared to male rats at several lower volumes of hypertonic saline injected into muscle, while males show significantly longer thermal paw withdrawal latencies at a higher volume (0.4ml) than females (Lei et al, 2011). Findings from the current study support and extend these earlier findings of sex differences in both acute and hyperalgesic models of nociception, with the notable finding that female antinociceptive responses, particularly in the hyperalgesic model, are greater than those of males.…”

Amitriptyline converts non-responders into responders to low-frequency electroacupuncture-induced analgesia in rats

“…Female rats were not used in this study because hormonal cycle might affect behavioral responses to noxious stimuli (Frye et al, 1993;Kayser et al, 1996). In addition, descending noradrenergic and serotonergic pathways, which are known to contribute with the analgesia induced by acupuncture (Zhao, 2008), were found to be differently involved in the action of descending modulations of nociception in rats of both sexes (Lei et al, 2011). Animals were housed two to a cage under controlled temperature (24 ± 2°C) with free access to (Zimmermann, 1983) guidelines were followed throughout the experiments.…”