Different analgesic effects of manual and electrical acupuncture stimulation of real and sham auricular points: a blind controlled study with rats.

Stimulation of the auricle is considered to be an effective analgesic technique. The aim of the present study is to establish whether there is a correspondence between somatic inflammation and the appearance of lower resistance points, and moreover, whether the stimulation of such points has an analgesic effect. The study has been conducted on 57 male Sprague-Dawley rats weighing between 120-140 g; 7 of them have been used to determine whether inflammation in the paw leads to the formation of lower resistance points on the auricle. The 50 remaining animals have been divided into 5 groups: Group 1 [12 animals], control were subjected to all manipulations with the exception of the auricle stimulation; Group 2 [12] was stimulated with manual acupuncture in the area corresponding to that observed in the above-mentioned first group of 7 animals; Group 3 [12] was stimulated with 5 Hz and 5 mA; electroacupuncture (EAP) Group 4 [8] and group 5 [6] were treated with acupuncture and with EAP respectively on points believed to be inactive in areas diametrically opposite to the ones observed in the first group. After acupuncture, 100 microg capsaicin in 50 microL of physiological solution were injected subcutis in the dorsal surface of the paw. Edema response was monitored for two hours, with measurement taken every 5 minutes. The results show a reduction in the edema response, only in the group treated with EAP on the appropriate points compared to the control group; no variation was observed in the sham groups. To conclude, the hypothesis of a somatotopic division would seem to be probable, and it would seem that the stimulation of the appropriate areas and the use of an appropriate intensity constitute the two main variables influencing the result.