Regular physical activity reduces the percentage of spinally projecting neurons that express mu-opioid receptors from the rostral ventromedial medulla in mice

Abstract

Physically active animals have less mu-opioid-expressing neurons projecting to the spinal cord in the rostral ventromedial medulla, but not the nucleus raphe obscurus/nucleus raphe pallidus, when compared to sedentary animals.

Consistent pattern between physical activity measures and chronic pain levels: the Tromsø Study 2015 to 2016

“…Several mechanisms might influence the relationship between physical activity and chronic pain. 7 , 31 , 32 , 38 , 47 – 49 Exercise-induced hypoalgesia (EIH) is a known response to exercise and refers to the decrease of pain sensitivity after bouts of acute exercise. 38 The underlying mechanisms behind EIH are complex and theorized to include several biological systems; for review, see Refs.…”

“… 34 This indicates that severity and distribution of chronic pain and chronic pain conditions may be of importance for the analgesic effect from exercise. However, findings from animal studies suggest that regular physical activity is of importance for preventing the development of chronic pain, 7 , 32 , 47 , 49 through different pathways, such as activation of inhibitory systems or by an increased level of anti-inflammatory mechanisms. 7 , 32 , 47 , 49 Such mechanistic studies are most often conducted in animals 7 , 31 , 32 , 38 , 47 , 49 or pain-free individuals, 38 and the clinical relevance for individuals with chronic pain conditions remains uncertain.…”

“…However, findings from animal studies suggest that regular physical activity is of importance for preventing the development of chronic pain, 7 , 32 , 47 , 49 through different pathways, such as activation of inhibitory systems or by an increased level of anti-inflammatory mechanisms. 7 , 32 , 47 , 49 Such mechanistic studies are most often conducted in animals 7 , 31 , 32 , 38 , 47 , 49 or pain-free individuals, 38 and the clinical relevance for individuals with chronic pain conditions remains uncertain. Additionally, other factors may contribute to more chronic pain among the physically inactive.…”

Exercise therapy for chronic pain: How does exercise change the limbic brain function?

“…Recently, it has been clinically noted that exercise suppresses pain, and it has been reported that pain-related behavior is suppressed by loading exercise on model animals of NPP (exercise-induced hypoalgesia: EIH). The mechanisms of the analgesic effect of voluntary exercise (EIH) have been proposed, which involve changes at various levels of the nervous system, such as the descending pain modulatory system ( Sluka et al, 2020 ) and the limbic system (for review, see Kami et al, 2017 , Kami et al, 2022 ; Senba and Kami, 2017 ). We also reported that the function of GABA neurons in the dorsal horn of the spinal cord is maintained by exercise ( Kami et al, 2016a , Senba and Kami, 2020 ).…”