Effects of acupuncture at ST-36 (Zusanli) on pain and associated sleep disturbance

Chronic pain significantly disrupts sleep, leading to a vicious cycle that negatively impacts well-being. Pharmacological treatments for pain and sleep disorders often have adverse effects, highlighting the need for alternative therapies. This study investigates the impact of acupuncture at ST-36 (Zusanli) acupoints on sleep disturbances in rats experiencing chronic inflammatory pain. Adult male Sprague-Dawley rats were subjected to inflammatory pain via subcutaneous injection of complete Freund's adjuvant (CFA) into the hind paw. Electroencephalogram (EEG) and electromyogram (EMG) recordings were used to assess the effects of acupuncture on sleep for 72 h post-treatment. Sleep stages, including non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, were scored. The role of the endogenous opioid system was evaluated by microinjecting naloxone into the nucleus tractus solitarius (NTS). Acupuncture significantly increased both NREM and REM sleep compared to baseline and improved pain-induced sleep disturbances by increasing total sleep time and reducing wakefulness. Naloxone microinjection into the NTS blocked acupuncture's sleep-promoting and analgesic effects, suggesting involvement of the endogenous opioid system. Additionally, pain thresholds, measured through paw withdrawal tests, were significantly elevated in acupuncture-treated rats, confirming the analgesic effects of acupuncture. In conclusion, acupuncture at ST-36 alleviates pain-induced sleep disturbances by enhancing sleep, potentially via activation of opioid receptors in the NTS. These findings support acupuncture as a promising non-pharmacological intervention for managing pain and associated sleep disturbances, with potential implications for treating insomnia in chronic pain patients.