Early Postoperative Nociceptive Threshold and Production of Brain-Derived Neurotrophic Factor Induced by Plantar Incision Are Not Influenced with Minocycline in a Rat: Role of Spinal Microglia

Abstract

Background: Brain-derived neurotrophic factor (BDNF) from spinal microglia is crucial for aberrant nociceptive signaling in several pathological pain conditions, including postoperative pain. We assess the contribution of spinal microglial activation and associated BDNF overexpression to the early post-incisional nociceptive threshold. Methods: Male Sprague-Dawley rats were implanted with an intrathecal catheter. A postoperative pain model was established by plantar incision. Thermal and mechanical nociceptive responses were assessed by infrared radiant heat and von Frey filaments before and after plantar incision. Rats were injected intrathecally the microglial activation inhibitor minocycline before incision, 24 h after incision, or both. Other groups were subjected to the same treatments and the L4-L5 spinal cord segment removed for immunohistochemical analysis of microglia activation and BNDF expression. Results: Plantar incision reduced both thermal latency and mechanical threshold, indicating thermal hypersensitivity and mechanical allodynia. Minocycline temporally reduced thermal withdrawal latency but had no effect on mechanical withdrawal threshold, spinal microglial activity, or dorsal horn BDNF overexpression during the early post-incision period. Conclusion: These results suggest that spinal microglia does not contribute substantially to post-incisional nociceptive threshold. The BDNF overexpression response that may contribute to postoperative hyperalgesia and allodynia is likely derived from other sources.

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“…Consequently, the use of distention models to study visceral pain syndromes in animals and humans facilitates the predictive success of findings from these models. Finally, incision pain models (typically involving incision to the plantar surface, tail, or gastrocnemius) are used to study acute postsurgical pain (Brennan, ; Kamerman et al, ; Kim et al, ; Spofford et al, ; Masaki et al, ; Zhu et al, ). These models closely recapitulate surgical pain in humans (Brennan, ) and have proved instrumental in understanding the pathogenesis and management of postsurgical pain.…”

Antinociceptive effect of Valeriana fauriei regulates BDNF signaling in an animal model of fibromyalgia

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Paeoniflorin Attenuates Inflammatory Pain by Inhibiting Microglial Activation and Akt-NF-κB Signaling in the Central Nervous System

“…Activation of microglia occurs in most pathological processes, which is often accompanied by morphologic change and production of cytotoxic molecules, and upregulation of phagocytosis and immune surface antigens [8][9][10]. Activation of microglia is also involved in the pain transmission pathway of acute and chronic pains such as neuropathic pain, inflammatory pain and cancerous pain [11][12][13].…”