ABSTRACT
This study aimed to investigate the analgesic effect of chlorogenic acid on cisplatin-induced neuropathic pain and explored the underlying molecular mechanisms. The animal experimental protocol has been reviewed and approved by Laboratory Animal Ethics Committee of Xinxiang Central Hospital, in compliance with the Institutional Animal Care Guidelines. Von Frey hair and a radiant heat was employed to measure mechanical allodynia and thermal hyperalgesia; Western blot was used to examine transient receptor potential vanilloid type-1 (TRPV1) protein expression in the rat dorsal root ganglion (DRG); patch clamp was used to record TRPV1 currents in DRG neurons. The experimental results showed that chlorogenic acid could attenuate cisplatin-induce mechanical allodynia and thermal hyperalgesia in rats. The expression of TRPV1 protein in DRGs was increased in cisplatin-treated rats, while chlorogenic acid also could reverse cisplatin-induced the upregulation of TRPV1 protein. Forthermore, chlorogenic acid could attenuate cisplatin-mediated the upregulation of TRPV1 current density. These above results indicated that chlorogenic acid could alleviate cisplatin-induced pain hypersensitivity through inhibition of the expression and function of TRPV1 in rats.
ABSTRACT
Early studies from several independent laboratories demonstrated that acupoints possess the characteristics of low electrical resistance. New devices are developing to increase the reliability of electrical skin impedance measurements for counteracting the factors including skin dryness, skin thickness, size of the sensing electrode, pressure applied on the electrode, interelectrode distance, room temperature, and humidity. Morphological studies have identified that blood vessels, hair follicles, and nervous components are enhanced in the meridians/acupoints, which represent areas of potentially high neuronal activity. Recent evidence shows that nitric oxide (NO) concentrations are enhanced in skin acupoints/meridians. L-arginine-derived NO synthesis modifies skin norepinephrine (NE) synthesis/release in acupoints/meridians, and NO-NE activations play an important role in mediating the skin conductance responses to electrical stimulation. NOergic signaling molecules interact with gap junction and transient receptor potential vanilloid type-1. Other studies reported that the high conductance at acupoints is a result of the release of the neuropeptides substance P and calcitonin gene-related peptide during neurogenic inflammation in the referred pain area. Pathological body conditions caused considerable changes in skin conductance or impedance at acupoints. Although systematic research with an improved equipment and research design to avoid the influencing factors are requested for a definite answer in this field, the results from anatomical and biochemical studies consistently show that acupoints exist higher levels of nervous components, and NOergic signaling molecules and neuropeptides involved in the skin low resistance at acupoints. The increased interest in the acupoints/meridians has led to an open-minded attitude towards understanding this system, which is fundamental important to establish the valid aspects of scientific basis of Chinese medicine mechanisms and therapies.