This study examined the responses of cultured adult rat trigeminal ganglion neurons to protons and to capsazepine and piperine, two substances known to produce pain and hyperalgesia in humans. Whole-cell patch clamp recordings were performed on cultured adult rat trigeminal ganglion(TG) neurons voltage-clamped near their resting membrane potential(-60mV). Piperine(10nM) caused a sustained inward current associated with either an increase or decrease in membrane conductance. When protons and piperine were coapplied, the membrane currents evoked in piperine-sensitive TG neurons far exceeded the algebraic sum of the responses to the two stimuli applied in isolation. Capsazepine blocked the response of TG neurons to piperine at both physiological and acidic pH. In the presence of capsazepine, responses to the mixture of piperine and protons resembled the response to a low pH stimulus applied alone. Capsazepine had no effect on sustained proton-induced current. These findings suggest that protons enhance piperine current by altering the vanilloid receptor/channel complex or by increasing the length constant of the space clamp. This study reveals that cultured trigeminal ganglion neurons show features of chemonociceptors and may provide a useful model for studying the mechanism of chemical pain production.
Adult ; Animals ; Humans ; Hydrogen-Ion Concentration ; Hyperalgesia ; Membranes ; Neurons* ; Protons ; Rats* ; Trigeminal Ganglion*

OBJECTIVE: Tremor, either essential tremor or Parkinsonian tremor, has been effectively and safely treated by lesioning the ventral intermediate(Vim) nucleus of the thalamus with or without mircroelectrode recording. The authors evaluate the treatment outcome of sixteen tremor patients who had been treated with thalamotomy without microelectrode. METHODS: Between September, 2001, and December, 2003, sixteen tremor patients were treated with thalamotomy without microelectrode recording. Twelve patients suffered from Parkinsonian tremor and four patients were essential tremor patients. The male to female ratio was 1.6 to 1 with median age of 59.6 years (range; 39-74 years). Under local anesthesia, a 3mm hole was made using a hand-held twist drill, and the dura mater was penetrated with a 1.2mm sharp drill beat. Radiofrequency(RF) electrode was placed in the Vim nucleus of thalamus. With intraoperative macrostimulation, RF lesion was made. Postoperative CT scan and/or MR imaging was performed to confirm the localization of the target lesioned. Preoperative and postoperative tremor was evaluated with simple tremor severity scale and the development of complications related with the procedure was closely reviewed at the immediate postoperative period and the last follow-up. RESULTS: It produces immediate relief in up to 98.4% of the patients. There were no development of complications related with procedure, all patients discharged one or two days after surgery. CONCLUSION: Vim thalamotomy without microelectrode recording is a safe and effective procedure to control the tremor with minimal morbidity. Intraoperative macroelectrode stimulation safely localizes the Vim nucleus target of the thalamus for the treatment of patients with tremor.
Anesthesia, Local ; Dura Mater ; Electrodes ; Essential Tremor ; Female ; Follow-Up Studies ; Humans ; Magnetic Resonance Imaging ; Male ; Microelectrodes* ; Postoperative Period ; Thalamus ; Tomography, X-Ray Computed ; Treatment Outcome ; Tremor