Issue Archive

Met-enkephalin-arg~(6)-phe~(7) like immunoreactive substances in periaqueductal gray of the rabbit have an analgesic effect and participate in electroacupuncture analgesia

Fei Hung, Zhou Zhongfu, Han Jisheng

Department of Physiology, Beijing Medical College. Beijing, China

Abstract

The present study was performed to evaluate the possible analgesic effect of a newly found C-terminal extended Met-enkephalin (Met-enkephalin-Arg~(6)-Phe~(7), MEAP) in periaqueductal gray (PAG) of the rabbit. Nociception was assessed by measuring the latency of the escape response (ERL) elicited by radiant heat focused on the snout of the rabbit. Captopril, the specific inhibitor of the MEAP degrading enzyme, when injected into PAG through chronically implanted intracranial. cannula at a dose of 240 nmol, produced marked analgesia which could be antagonized by MEAP antiserum (1#mu#l) injected into the same site. Antiserum directed to Met-enkephalin (ME) was not effective at this extent. Microinjection of captopril into PAG at a dose of 60 nmol caused marked potentiation of the effect of electroacupuncture (EA) analgesia. This potentiating effect was completely eliminated by microinjection of 1#mu#l of MEAP antiserum into PAG, being ineffective at a dose of 0.1 #mu#l. These findings suggest that the MEAD-like imrriunoreactive substance in PAG of the rabbit may have an analgesic effect and may play an important role in mediating EA analgesia.

Key words: Met-enkephalin-Arg~(6)-Phe~(7);Captopril;Analgesia;Electroacupuncture analgesia;Periaqueductal gray;Antisera

Received: 　　Accepted:

Corresponding author: 　　E-mail:

Citing This Article：

Fei Hung, Zhou Zhongfu, Han Jisheng. Met-enkephalin-arg~(6)-phe~(7) like immunoreactive substances in periaqueductal gray of the rabbit have an analgesic effect and participate in electroacupuncture analgesia. Acta Physiol Sin 1985; 37 (1): (in Chinese with English abstract).