Modulation of Corydalis tuber on Glycine-Induced Ion Current in Acutely Dissociated Rat Periaqueductal Gray Neurons

Abstract

Corydalis tuber is the root of Corydalis yahusuo W. T. WANG classified as Papaveraceae. Aqueous extract from Corydalis tuber is known to stimulate blood circulation and relieve pain. It has traditionally been used for the treatment of neuralgia, dysmenorrhea, and gastrointestinal spasm. 1)The analgesic and spasmolytic properties of the Corydalis tuber are essentially ascribed to several alkaloids: DL-tetrahydropalmatine (THP), D-cotydaline, and corydalis H, I, J, K, and L. The alkaloids exhibited analgesic, antiarrhythmic, antithrombic, antiinflammatory, anticataractic, antihypertensive, and antiallergic activities.2) Among others, THP is a very effective monoamine depletor in the brain and also possesses analgesic, sedative, hypnotic, and antihypertensive actions.3)The transmission of nociceptive information may be altered by various neuronal circuits within the central nervous system (CNS). One of them is a descending pain control system, which consists of three major components: the periaqueductal gray (PAG) of the midbrain, the rostroventral medulla (RM) including the nucleus raphe magnus, and the spinal dorsal horn. Of these, modulation of pain in the PAG matter is the most extensively studied pain control system. 4,5) PAG is known as a major target of analgesic action of the opioid in the CNS. 6) Stimulation within the midbrain PAG produces an opioid receptor-mediated analgesia. 7)Opioid peptides and opiates produce analgesia by activating the descending pain modulatory pathways, especially at the level of the PAG. 4,8,9) They also regulate the nociceptive transmission in part by inhibiting the release of transmitters.8,10) The effects of opiates and opioid peptides also have been reported to activate potassium channels 11,12) or to inhibit calcium channels. 13,14) It is proposed that endogenous opioid peptides can activate PAG output neurons by inhibiting inhibitory interneurons. 5)The amino acid glycine is a major inhibitory neurotransmitter in the brain and spinal cord. The inhibitory action of glycine is mediated by a strychnine-sensitive glycine receptor and a glycine-gated chloride ion channel. Inhibitory glycine synapses in the brainstem and spinal cord are closely implicated in the transmission of nociception, in which glycine inhibits neurotransmission and relieves pain. In addition, the glycine-mediated inhibitory effect induces muscle relaxation, whereas inhibition of glycine receptors by strychnine induces convulsion. 15,16) The analgesic mechanism of Corydalis tuber in the context of the descending pain control system has not yet been clarified. In the present study, the modulation of Corydalis tuber on glycine-activated ion current in the acutely dissociated PAG neurons was investigated using a nystatin-perforated patch-clamp technique under voltage-clamp conditions. MATERIALS AND METHODS Preparation of PAG NeuronsThe PAG neurons were freshly dissociated using a technique described elsewhere. 9,13) In brief, 10-to 15-d-old Sprague-Dawley rats of both sexes were decapitated under Zoletil 50 ® ...

Modulation of the aqueous extract of Bupleuri radix on glycine-induced current in the acutely dissociated rat periaqueductal gray neurons

“…In addition, Gurwitz (2001) reported that inhibition of glycine transporter in the brain and spinal cord may relieve pain. Recently, it was suggested that the analgesic effects of Oriental medicinal herbs such as Corydalis tuber and Chelidonii herba are closely related to the inhibition on glycine in the PAG neurons (Shin et al, 2003;Cheong et al, 2004). The present results showed the possibility that Bupleuri radix may have an analgesic effect by activating the descending pain control system through the inhibition on glycine-induced ion current in PAG neurons.…”

“…It is well documented that analgesic action of PAG is mediated by opioid system (Shin et al, 2003;Cheong et al, 2004). Pert and Walter (1976) reported that administration of naloxone, nonselective opioid receptor antagonist, to rats reduced analgesic effect induced by electrical stimulation on the PAG.…”

Effects of Herbal Bath "HAC" on Functional Recovery and c-Fos Expression in the Ventrolateral Periaqueductal Gray Region after Sciatic Crushed Nerve Injury in Rats

“…Shin et al (2003) demonstrated that Chelidonii herba increases neuronal excitability in PAG, which results in activation of descending pain control system and may contribute as a potential mechanism of the analgesic actions of Chelidonii herba. Cheong et al (2004) also reported that application of Corydalis tuber onto PAG neurons modulates glycine-activated ion current in the PAG neurons, which exerts analgesic action.…”

“…Aqueous extract from Corydalis tuber has been used as an analgesic and for the treatment of inflammatory and allergic diseases (Sagare et al, 2000). The analgesic action of Corydalis tuber is closely associated with descending pain control system (Cheong et al, 2004).…”

Effects of amygdalin on the functional recovery and c-Fos expression in the ventrolateral periaqueductal gray region after sciatic crushed nerve injury in rats

“…Shin et al (2003) demonstrated that Chelidonii herba increases neuronal excitability in PAG, which results in activation of descending pain control system and may contribute as a potential mechanism of the analgesic actions of Chelidonii herba. Cheong et al (2004) also reported that application of Corydalis tuber onto PAG neurons modulates glycine-activated ion current in the PAG neurons, which exerts analgesic action. The SFI derived from walking track analysis in rats provides a reliable and easily quantifiable method for the assessing of motor function after sciatic nerve injury (Varejo et al, 2003).…”