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KMID : 1129720030200040017
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Korean Journal of Acupuncture
2003 Volume.20 No. 4 p.17 ~ p.29
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Modulation of Harpagophytum procumbens on ion channels in acutely dissociated periaqueductal gray neurons of rats
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Shin Min-Chul
Chang Hyun-Kyung
Jang Mi-Hyeon
Kim Chang-Ju
Kim Youn-Hee
Kim E-Hwa
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Abstract
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Harpagophytum procumbens (generally known as Devil’s claw) has been used for the treatment of inflammatory arthritis, and inflammatory bowel disorders1,2). The anti-inflammatory and analgesic properties of the Harpagophytum procumbens are essentially ascribed to the sum of the three phenolic glycosides; acteoside, isoacteoside, and bioside3). There are many reports on the phytochemical4) and biological aspects5,6) of this plant. Pharmacological studies have shown that Harpagophytum procumbens possesses analgesic, antiphlogistic, and antiinflammatory actions and it improves motility and reduces sensitivity to pain7). The transmission of nociceptive information may be altered by various neuronal circuits within the central nervous system (CNS). The descending pain control system consists of three major components: the periaqueductal gray (PAG) of the midbrain, the rostroventral medulla including the nucleus raphe magnus, and the spinal dorsal horn. Descending modulation of spinal nociceptive neurons by the PAG matter is one of the most extensively studied pain control systems8). Several neurotransmitters in the PAG participate in the control of nociception. Among these, endogenous opioids, GABA, glycine, and glutamate seem to play a crucial role in the processing of pain regulatory signals within this area9,10). γ-Aminobutyric acid (GABA) and glycine are a key inhibitory transmitters in the brainstem and the spinal cord. In the PAG and the spinal dorsal horn, the relay centers for pain and sensory information, GABA and glycine inhibits glutamate- evoked depolarization and represses the firing of neurons. The binding of GABA and glycine to its receptor produces a large increase in Cl- conductance, which causes membrane hyperpolarization11). Glutamate is excitatory neurotransmitters in the brain and abundant glutamate binding sites have been localized in the dorsolateral subdivision of the PAG12). Glutamate seems to be involved in PAG mediated analgesia. Microinjection of glutamate or glutamate agonists into the PAG neurons induced analgesic effect13-15). In this study, modulatory action of Harpagophytum procumbens on inhibitory neurotransmitter-activated ion currents (GABA- and glycine-activated ion currents) and excitatory neurotransmitter-activated ion currents (glutamate-activated ion current) in acutely dissociated PAG neurons was investigated using nystatin-perforated patch-clamp technique under voltage-clamp condition.
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KEYWORD
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Harpagophytum procumben, Patch clamp, Periaqueductal gray, GABA, glycine, glutamate mate
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