It is a problem to be solved whether the blocking of propagated sensanti- in along channels(BPSC)induced by local cooling is resulted from the sens- ory dysfunction of somatosensory system or other causes.In order to clarify the problem

an observation on the variation of the cortical sensory evoked potential(SEP)and evoked action potential(AP)of sensory nerve concern- ed with the acupoint stimulated during BPSC has been carried out in this wo- rk. Eighteen subjects with marked propagated sensation along channels(PSC) and 11 without PSC were studied.The acupoint punctured was Hegu and Sh- ousanli was cooled with a small ice bag.The action potential was receded from the radial nerve of upper arm ipsilateral to the stimulated side and SEP from the area of arm representation contralateral to the stimulatied side. The observation of the influence of local cooling on these two potentials was carried out on different day. The resuls are as follows: In all cases BPSC developed gradually

and so did the recovery of PSC after removal of ice bag.The results of measuement of the temperature of deep tisse underneath the acupoint“Shousanli”in 9 subjects showed that the critical temperature for BPSC and recovery of PSC was 21.16±0.4℃.The peak latency and the duration of AP during local cooling lasted 3.4% and 7.5% longer than those before cooling respectively.There was no striking change in the amplitudes of AP.The rates of variation of the peak latency

duration and amplitude of SFP potential complex P_(60)-N_(75)-P_(95)during cooling were 0.7%

1.6% and 3.9% resectively. The results indicate that local cooling could completely block FSC

but only slightly effect the AP of sensory nerve and SEP of SI of cerebral cor- tex.It is thus evident that BPSC induced by local cooling was irrelevant to the dysfunction of the sensory nerve

as the afferent signals from Hegu could still be able to normally transmit to central nervous system.It didn’t resulted from the interference of the two afferent signals in the first soma- tosensory area of cerebral cortex either

as the response of SI to acupuncture remained unchanged.It follows that BPSC might result from the blo- eking of a certain substantial process advancing along the channel in periphery. This process is not only susceptible to the influence of mechanical pressure

but also highly temperature-dependant in nature.This is an important clue for the further elucidation of the mechanism of BPSC and the essence of this particular substantial process proceeding along the channels.