Chronic primary pain (CPP) is a group of diseases with long-term pain and functional disorders but without structural or specific tissue pathologies. CPP is becoming a serious health problem in clinical practice due to the unknown cause of intractable pain and high cost of health care yet has not been satisfactorily addressed. During the past decades, a significant role for the descending pain modulation and alterations due to specific diseases of CPP has been emphasized. It has been widely established that central sensitization and alterations in neuroplasticity induced by the enhancement of descending pain facilitation and/or the impairment of descending pain inhibition can explain many chronic pain states including CPP. The descending serotonergic neurons in the raphe nuclei target receptors along the descending pain circuits and exert either pro- or antinociceptive effects in different pain conditions. In this review, we summarize the possible underlying descending pain regulation mechanisms in CPP and the role of serotonin, thus providing evidence for potential application of analgesic medications based on the serotonergic system in CPP patients.

中文翻译：

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疼痛调节在慢性原发性疼痛中的作用：靶向血清5-羟色胺能系统的药物的潜在应用。

慢性原发性疼痛（CPP）是一类具有长期疼痛和功能障碍，但没有结构或特定组织病理学的疾病。由于不明原因的顽固性疼痛和高昂的医疗保健费用，CPP在临床实践中正成为一个严重的健康问题，但尚未得到令人满意的解决。在过去的几十年中，人们一直在强调由于CPP特定疾病引起的下行疼痛调节和改变的重要作用。已经广泛建立的是，由降低疼痛的促进促进和/或降低疼痛抑制的抑制作用引起的中枢敏化和神经可塑性的改变可以解释许多慢性疼痛状态，包括CPP。缝核中的下降性血清素能神经元沿着疼痛的下行回路靶向受体，并在不同的疼痛状况下发挥促伤害性或抗伤害性作用。在这篇综述中，我们总结了在CPP中可能的潜在的下行疼痛调节机制以及血清素的作用，从而为在CPP患者中基于血清素能系统的止痛药的潜在应用提供了证据。