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Low rather than high dose lipopolysaccharide ‘priming’ of muscle provides an animal model of persistent elevated mechanical sensitivity for the study of chronic pain
Author(s) -
Yamaguchil Yoshiko,
Hashimoto Tatsuyuki,
Sakurai Hiroki,
Yoshimoto Takahiko,
Ohmichi Yusuke,
Morimoto Atsuko,
Harimoto Kohei,
Ohmichi Mika,
Eguchi Kunihiro,
Kumazawa Takao
Publication year - 2011
Publication title -
european journal of pain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.305
H-Index - 109
eISSN - 1532-2149
pISSN - 1090-3801
DOI - 10.1016/j.ejpain.2011.01.001
Subject(s) - medicine , hypertonic saline , chronic pain , noxious stimulus , nociception , stimulation , pathogenesis , nociceptor , anesthesia , hyperalgesia , lipopolysaccharide , immunology , receptor , psychiatry
Abstract Experimental animal pain models involving peripheral nerve lesions have expanded the understanding of the pathological changes caused by nerve damage. However models for the pathogenesis of chronic pain patients lacking obvious nerve injuries have not been developed to the same extent. Guided by clinical observations, we focused on the initiating noxious event, the context when applying nociceptive stimulation targeting long‐lasting pain elicited by muscle insult. The administration of a nociceptive agent (6% hypertonic saline: HS; 5‐time repeated‐injection: HS5) after pretreatment with an immuno‐inflammatory agent (lipopolysaccharide: LPS, 2μg/kg) into one gastrocnemius muscle produced markedly long‐persisting biphasic sustained mechanical hypersensitivity on the plantar surface of both hindpaws. In the acute phase, the blockade of afferent inputs from the injected‐site was effective in returning the contralateral enhanced‐responses to baseline levels. In contrast, similar blockade during the chronic phase did not affect the contralateral enhanced‐responses, indicating that the hypersensitivity in the two phases was probably induced by different mechanisms. However, increasing the dose of LPS (20μg/kg) before applying HS5 eliminated the development of mechanical hypersensitivity in the chronic phase, while the hypersensitivity in the acute phase was significantly more severe than with low‐dose LPS‐pretreatment. In this model, the development of hypersensitivity could be modulated by manipulating LPS‐doses prior to noxious stimulation. This novel chronic pain model based on a preceding ‘priming’ myalgic stimulus provides an intriguing means for studying the pathogenesis of chronic pain.