[Corticofugal modulation of somatosensory area II on acupuncture effect in nucleus ventralis posterolateralis of the thalamus].

In order to explore whether cortical somatosensory area 11 (SII) was involved in descending modulation of the effect of electroacupuncture (EA) on nucleus ventralis posterolateralis (VPL), the present study was designed to investigate the influence of topical application of lidocaine at SII on the EA effects in VPL nucleus. Experiments were performed on 23 adult cats anaesthetized with pentobarbital sodium (35-40 mg/kg i.p.) and immobilized with gallamine triethiodide. The single unit activities of VPL neurons were extracellularly recorded using glass microelectrodes. The results were as follows: 1. The nociceptive responses of VPL were obviously attenuated after EA at "Huantiao (G30)" and "Yanlingquan (G34)". The difference was statistically significant at 0-10 minutes after cessation of EA (n = 13, P < 0.001 or P < 0.05), then it was gradually recovered. The results showed that EA could inhibit the nociceptive responses of VPL neurons. 2. The inhibitory effect of acupuncture on nociceptive responses were reduced or abolished after topical application of lidocaine (n = 14, P > 0.05). However, it exerted marked inhibition at 0-10 minutes after cessation of EA in the saline control group (n = 14, P < 0.05). There was a statistical difference between these two groups (P < 0.05). The results showed that SII was involved in descending modulation of acupuncture effect in VPL nucleus.