[Effect of electroacupuncture tolerance by different frequencies on the cardiovascular inhibition of spinal opioid peptides of the rats].

Continuous 6 hour's electroacupuncture (EA) of 2-15Hz or 2Hz applying to both legs of the rats resulted in the electroacupuncture tolerance (ET). Then, we observed: (1) The effect of 2-15Hz ET on the recovery of mean arterial blood pressure (MAP) and heart rate (HR) of rats after hemorrhagic shock; (2) The change in MAP and HR of rats subjected to 2Hz ET after intrathecally (i. t.) administration of DADLE 25 micrograms, a delta opioid agonist. The results showed that, firstly, there was no difference between 2-15Hz ET group and control group in the recovery of MAp and HR after hemorrhagic shock. Secondly, DADLE (25 micrograms) caused almost the same suppression effect both in 2Hz TE group and in control group. These results suggest that unlike the spinal dorsal horn cells (regulating algesia, the spinal lateral horn cells (regulating blood pressure) are insensitive during EA analgesia and can not be made tolerance to continuous EA.