ラット歯髄から視床・大脳皮質への投射路の解析および歯髄電気刺激による皮質誘発電位に対するMorphineとBarbiturateの影響について

抄録

Pain pathways from the tooth pulp to the somatosensory cortex and the effects of morphine and barbiturate on the cortical responses evoked by the stimulation of the pulp were investigated electrophysiologically in rats. 1) Responses to the tooth pulp stimulation (contra- and ipsilateral) were recorded from the somatosensory face area I (SI) and II (SID. Latency of the response in SII was longer than that in SI. The latencies of the ipsilateral responses in SII were 2.5-3.0 msec longer than those of the contralateral responses and the ipsilateral responses were eliminated by acute ablation of the opposite cortex including SI and SII. 2) Although the contralateral responses in SI were significantly depressed by morphine (2.5, 5 and 10 mg/kg i. p.), the depression did not depend on the dose of morphine. The ipsilateral responses were significantly emphanced by morphine (5 and 10 mg/kg). 3) The contra- and ipsilateral responses in SII were significantly depressed by morphine and these depression depended on the dose of morphine. 4) The contra- and ipsilateral responses in SI and SII were essentially unchanged by pentobarbital sodium (4, 8 and 16 mg/kg), but the ipsilateral responses were enhanced. 5) All responses except the ipsilateral surface positive response in SI were significantly depressed by a high dose of pentobarbital sodium (32 mg/kg). The results obtained suggest that this somatosensory face area II and the pathway to this area from the tooth pulp may play an important role in the mechanism of pain.