Acupuncture modulation of capsaicin-induced inflammation: effect of intraperitoneal and local administration of naloxone in rats. A blinded controlled study.
OBJECTIVE
It is believed that acupunctural stimulation induces an analgesic response mainly through a central mechanism: that is, through an increase in the production of opioid peptides and their release at different levels in the nervous system. We sought to establish whether the modulating effect of acupuncture on experimental neurogenic edema can be attributed to a central mechanism only or whether a peripheral mechanism could also exist. Intraperitoneal administration was compared to local administration in the same paw in rats that were injected with capsaicin and in the same dermatome of the acupunctural stimulation.


METHODS
Experimentation was conducted on 105 male Sprague-Dawley rats weighing 180-220 g, divided into 7 groups as follows: group 1, control; groups 2-4 (15 animals), stimulated with manual acupuncture; group 3 also treated with intraperitoneal naloxone 1 mg/kg; group 4 also treated locally with naloxone (20 microg); groups 5-7 (15 animals), stimulated with 5 Hz and 5 mA electroacupuncture (EAP); group 6 also treated with intraperitoneal naloxone, 1 mg/kg, group 7 also treated locally with naloxone (20 microg).


RESULTS
The results indicate that the administration of 1 mg/kg of naloxone intraperitoneally can inhibit the modulating effect of acupunctural stimulation. Equally effective in inhibiting the modulating effect of acupunctural stimulation, although not having a systemic effect, is a 20-microg dose of naloxone administered peripherally on the site of edema induction.


CONCLUSIONS
It is possible to conclude that both systemic and peripheral mechanisms seem to be implicated in the modulating effect of acupuncture on the neurogenic inflammation mechanism.
Ceccherelli
Francesco
F
Osservatorio per le Medicine non Convenzionali della Regione Veneto Anesthesiological Unit of the Department of Pharmacology and Anesthesiology, University of Padova, Italy. istaneri@unipd.it
Gagliardi
Giuseppe
G
Ruzzante
Leonardo
L
Giron
Giampiero
G
D000818:Animals; D002211:Capsaicin / Q000009:adverse effects*; D004487:Edema / Q000139:chemically induced / Q000628:therapy; D015671:Electroacupuncture; D007274:Injections, Intraperitoneal; D007279:Injections, Subcutaneous; D008297:Male; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D020078:Neurogenic Inflammation / Q000139:chemically induced / Q000188:drug therapy / Q000628:therapy*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D016037:Single-Blind Method
D009292:Narcotic Antagonists; D009270:Naloxone; D002211:Capsaicin