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Inhibitory effect on nociceptive discharges of parafascicular neurones of thalamus by electrical stimulation of nucleus centrum medianum at different frequencies

Lo Fusun, Yuan Chunsu, Yang Shanlu, Zhang Xiangtong

Shanghai Brain Research Institute, Academia Sinica. Shanghai, China

Abstract

In waking and Flaxedil-immobilized cats, the nociceptive discharges of parafascicular neurones could be inhibited by electrical stimulation of the centromedian nucleus at frequencies of 4 Hz, 8 Hz and 60 Hz. Comparison of the results showed that 8 Hz stimulation was the optimal frequency for producing the inhibitory effect on nociceptive discharges, 4 Hz was slightly less effective and 60 Hz the least. There were two ways in which the inhibitory effect showed itself as revealed in the oscilographic records: (1) a brief arrest for about 120 ms of nociceptive discharges following each shock at low frequency, (2) shortening of the overall duration of the nociceptive response which also varied with the stimulus intensity within the range of 5.4-8.5 V. Electrical stimulation of “acupuncture points” or of the deep branch of a somatic nerve produced the same inhibitory effect as did the stimulation of the centromedian nucleus so far as the relative effectiveness of different stimulus frequencies was concerned. Stimulation of centromedian nucleus could inhibit selectively the nociceptive neurones in parafascicular nucleus without any effect on the activity of non-nociceptive neurones. The result of the present study suggests that nucleus centrum medianum probably plays an important role, in the mechanism of analgesia of distant acupuncturing.

Key words: Thalamus;Parafascicular nucleus;Nociceptive discharges;Acupuncture analgesia

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Citing This Article：

Lo Fusun, Yuan Chunsu, Yang Shanlu, Zhang Xiangtong. Inhibitory effect on nociceptive discharges of parafascicular neurones of thalamus by electrical stimulation of nucleus centrum medianum at different frequencies. Acta Physiol Sin 1985; 37 (1): (in Chinese with English abstract).