1. 2025;28;E73-E79Mode of Action of Amitriptyline Against Neuropathic Pain via Specific NF-kB Pathway Suppression
   Animal Trial
   YouMi Hwang, MD, PhD, and So Young Kwon, MD, PhD.

BACKGROUND: Neuropathic pain occurs for various reasons involving adenosine receptors. One of several drugs used to control neuropathic pain is amitriptyline, a tricyclic antidepressant. Amitriptyline has an antinociceptive effect on the A3 adenosine receptor (A3AR). However, the exact mechanisms underlying A3AR activation remain unclear.

OBJECTIVES: By investigating the effects of amitriptyline on neuropathic pain mitigation and its impact on inflammatory pathways via A3AR activation, we aimed to provide novel insights into the potential mechanisms of action of amitriptyline in neuropathic pain management. These insights could potentially revolutionize the way we understand and treat neuropathic pain.

STUDY DESIGN: We used Sprague-Dawley rats for the neuropathic pain models. The rats were sorted into the sham (control), neuropathic pain (NP+NS), and neuropathic pain and amitriptyline (NP+AMI) groups. Each group consisted of 8 rats. This design allowed us to compare the effects of amitriptyline on neuropathic pain in a control group and a group that experienced neuropathic pain without amitriptyline treatment.

SETTING: St. Vincent’s hospital, research institute of medical science.

METHODS: Normal saline and amitriptyline were injected intraperitoneally into rats using a subcutaneously implanted osmotic pump. A week after the procedure, nuclear factor kappa B (NF-kB) and a related proinflammatory cytokine (TNF-a) were quantified using immunoblotting or reverse-transcription PCR.

RESULTS: Our results brought positive news. The NF-kB concentrations of the groups were not different from one another, indicating a stable baseline. The control and NP+NS groups showed relatively increased activation of the mu-opioid receptor (MOR) and proinflammatory cytokines, including TNF-a, but demonstrated no intergroup difference. However, the MOR and TNF-a concentrations were markedly lower in the NP+AMI group than in the control or NP+NS groups (P = 0.02, 0.002, respectively). This difference suggests a potential for amitriptyline to reduce inflammation. The paw withdrawal threshold test revealed a recovery response to mechanical allodynia for the NP+AMI group (P < 0.05), indicating a positive impact on neuropathic pain.

LIMITATIONS: The experiment involved only a few mice, so the results may not be generalizable.

CONCLUSIONS: The release of proinflammatory cytokines via NF-kB expression and subsequent inflammatory responses is significantly associated with the development of neuropathic pain. Our study reveals that AMI effectively suppresses NF-kB-related proinflammatory cytokines, offering a promising avenue for treating pain related to peripheral nerve injuries. These findings provide valuable insights into neuropathic pain management.

KEY WORDS: amitriptyline, neuropathic pain, NF-kB, TNF- a