Hypnotic analgesia versus pain-control suggestions in the self control of post operative pain

S179 NOP~ADRENERGICMECHANISM INVOLVED IN ELECTROACUPUNCTURE 214 S l i d e ANALGESIA IN RATS, K. Takeda, H. Kuriyama, T. Nakajima* Thu 14:00 and A. Matsushita, Department of Otolaryngology, Osaka Theotre Medical College, Takatsuki, Osaka 569, Japan INTRODUCTION: In 2nd World Congress on Pain, we presented the data favoring the theory of p a r t i c i p a t i o n of endogenous opioid substances in electroacupuncture (EAP) analgesia on rabbit pain reactions to bradykinin (BK). Since no complete antagonism by naloxone of the EAP analgesia was observed, i t was considered that p a r t i c i p a t i o n s of some other neurochemical substances were possible. METHODS: The experiments were conducted on male Wistar rats weighing 250 to 330g. (I) The test was based on the D'Amour-Smith method in which the t a i l was exposed to a hot noxious stimulus, and the time required for the animal to f l i c k the t a i l was recorded. ( I I ) Multiple unitary responses in the thalamus (CM-PF) of chloralose-rats were observed following BK i n j e c t i o n s into the subclavian or the femoral artery. In both experiments, electrode pairs for EAP were placed on the acupuncture points which corresponded to Li-4 or B-34 in man. The electrodes were connected to an EAP stimulator of Chinese type. Stimulus frequency was kept at 4 Hz. RESULTS: Reaction times were elevated by EAP in about 70% of the rats. In general, the effects lasted for 2-4 hours a f t e r cessation of EAP. A s h o r t - l a s t i n g antagonism by t o l a z o l i n e (20 mg/kg, i . p . ) of EAP analgesia was observed. ( I I ) Noxious responses in the thalamus were suppressed during and a f t e r EAP in about 50% of the animals. The suppressed response was p a r t i a l l y antagonized by t o l a z o l i n e , but not by phenoxybenzamine and chlorpromazine. CONCLUSIONS: These results suggest that observed EAP analgesia is affected in part by changes i n ~ 2 - a d r e n e r g i c a c t i v i t i e s . iNTRATHECAL OR SYSTEMIC NALOXONE ANTAGONIZES TNS ANALGESIA I 215 Slide IN THE RAT. J.M.Peets* and B.Pomeranz, Department of Zoolog~ Thu 14:15 University of Toronto, Toronto, Ontario, Canada M5S IAI. [ Theoire 8 Aim; It has been suggested that transcutaneous nerve stimulation (TNS) analgesia may be mediated at least in part by endorphins. The present study tested this possibility using naloxone injected either subcutaneously or intrathecally in rats receiving TNS. Methods: Four groups of I5 rats were given TNS. Two groups of rats in which the lower lumbar spinal cord was accessed by a chronic intrathecal catheter received either naloxone HCI (I0 uL, I mg/ml) or artificial CSF. Two groups of umoperated rats received subcutaneous saline or naloxone (2 mg/kg). TNS consisted of 30 minutes of acupuncture-like trains of pulses given to the hindleg at currents below noxious threshold. Pain threshold was determined by tail flick latency before and after treatments. Results: The data show a moderate but significant increase in pain threshold over baseline following TNS.This increase was slow in onset and lasted from I0 to 30 minutes after cessation of TNS. The effect was strongly antagonized by either systemic or intrathecal injection of naloxone. Conclusions: Since TNS analgesia was reversed by naloxone injection via either route of administration, it is proposed that endorphins may be involved in the analgesia produced by TNS. Systemic injection does not allow any speculation as to the location of the endorphin effect. The Effectiveness of the spinal injectionof naloxone, however, implies that at least one site of action of endorphins is localized in the spinal cord. This proposal is cosistent with the observations of Terenius' group that spinal CSF endorphins rise following TNS in humans.