[Analgesia by injection of morphine and antagonism of electro-acupuncture analgesia by injection of naloxone into septal area of rabbits].
The present work was carried out to investigate the role of the septal area in morphine and acupuncture analgesia in rabbits. Electrophoresis of K+ into the skin of rabbit's ear serving as the noxious stimulus and the minimal electric current required to produce the defense motor response of the head and forelimbs were taken as pain threshold. 
 Twenty-one min after bilateral microinjections of morphine (40μg / 2μl) through chronically implanted cannulae into the septal area, the pain threshold increased markdly and lasted more than 2 h. The rate of increase was 65±(SD)12% within 21-60 min and it revealed a significant difference as compared with the control values (10 rabbits). No noticeable change was found in the control experiments (10 rabbits). 
 Fifteen min after bilateral injections of etorphine (4μg/2μl) into the septal area, the pain threshold increased strikingly in 15-51 min (P<0.05 or P<0.01). The av rate of increases was 89±18%. Naloxone iv reversed the analgesia from etorphine in 8 out of 9 rabbits, whereas normal saline had no effect on 7 rabbits. No definite effect could be found after microinjection of etorphine into the white matter of the cortex and the tail of caudate nucleus. 
 The analgesic effect of electro-acupuncture was reversed 3 min after bilateral injections of naloxone (2μg/2μl) into the septal area in 12 out of 15 rabbits, with a maximal reversal at 15 min later (P< 0.01). No significant change was found in the control group of saline injections (10 rabbits). 
 The results suggest that the septal area is one of the sites for the action of morphine and the opiate receptors in that area are partially related to electro-acupuncture analgesia.