The effects of the nucleus central lateralis (CL ) on the unit discharges evoked by the splanchnic afferents in the posterior group of thalamic nuclei (PO) were studied with extracellular microelectrode techniques. In 35 cate. 96 units (98％)producing evoked discharges in PO with the latency range of 30 -150ms were observed. The evoked discharges of 69 units in PO were depressed by stimulating CL with a short train of electric pulse through a hipolar electrode

but the other 27 units were uninfluenced. The inhibition of CL can be classified into 3 forms: the instant inhibition

the delayed inhibition and the continued inhibition. The injection of picrotoxin (1‰

40μl) into lateral ventricles of the brain could invertthe inhibitory effects of PO cells caused by stimulating CL. The results suggest that there may be direct neryous pathway from CL to PO and some of these neurons may function with GABA with GABA as neurotran mitter .The GABA The CL may execute the instant inhihition through the nervous pathway.It is conefuded that CLhas mbibitory effect on visceral pain and GABA is involved in the inhibitory process.