Effect of ACTH on pain behavior and the level of brain-derived neurotrophic factor and corticotropin-releasing hormone in the hippocampus of rats with chronic pain

AIM: To observe the effect of adrenocorticotropic hormone(ACTH) on the levels of brain-derived neurotrophic factor(BDNF), trkB and corticotropin-releasing hormone(CRH) in the hippocampus of arthritic rats.METHODS: The BDNF immunoreactivity(IR) and CRH-positive neurons were stained with immunohistochemistry and in situ hybridization methods, respectively.RESULTS: The BDNF-IR, CRH mRNA-positive neurons in the contralateral hippocampus of the arthritic rats were increased significantly, which was decreased markedly by intraperitoneal injection of ACTH. However, the effect of ACTH was attenuated after adrenalectomy(ADX).CONCLUSION: These results suggest that BDNF and CRH in the hippocampus of arthritic rats were involved in the modulation of chronic pain, ACTH produced its analgesic effect by inhibiting the increase in BDNF and CRF level. Adrenal is critical to the analgesic action of ACTH.