Zhen Ci Yan Jiu. 1990 ; 15(1): 6-12.

[The effects of microinjection of TRH or morphine into unilateral nucleus septum on pain threshold and electroacupuncture analgesia in rats]

Tu Z, Zhang Z, Zhu Z.

Department of Physiology, Faculty of Basic Medical Sciences, Tongji Medical University, Wuhan.

Experiments were performed on awake rats. The pain threshold (tail flick latency, TFL) was measured with radiant heat tail-flick method. Microinjection of thyrotropin releasing hormone (TRH 2.5 micrograms/1 microliter) into septal area can increase remarkably and last 40 min, but the analgesic effect can not be reversed by the opioid receptor blocker naloxone (NAL) into the septal area; injection 10 micrograms of morphine into unilateral septal nucleus, the pain threshold had no obvious change; the after-effect of electroacupuncture (EA) was remarkably prolonged injecting TRH (1.5 micrograms) into unilateral septal nucleus. The after-effect of EA caused by TRH could abolish by NAL. The results imply that (1) microinjection of TRH into the unilateral septal nucleus could raise TFL, intraseptal opiate receptors may not be involved in analgesic effect elicited by TRH. (2) morphine was injection into unilateral septal nucleus having no effect on TFL, suggesting that endogenous opioid peptides in the septal nuclei might not be the major role in anti-nociceptive reaction in rats. (3) Microinjection TRH into the intraseptal can obviously prolong the after-effect of EA, NAL could abolish it, indicating that endogenous opiate peptides in the septal nuclei may play a role partially in mediating EA analgesia.