Effects of nitric oxide and noradrenergic function on skin electric resistance of acupoints and meridians.
OBJECTIVE
The objectives of this study were to determine the effects of L-arginine-derived nitric oxide (NO) synthesis and noradrenergic function on skin electrical resistance of acupoints and meridians.


METHODS
Experiments were performed on male Sprague-Dawley rats anesthetized with sodium pentobarbital. Low skin-resistance points (LSRP; BL 56, PC 6, CV 17), non-LSRP positions (along the meridians), and non- LSRP, non-meridian control positions (adjacent to but not along the meridians) were determined on the skin surface by measurements of the skin stimulus-evoked electrical currents. The effects of L-arginine-derived NO synthesis and noradrenergic function on the currents, representing skin electrical resistance, were examined in the LSRP, non-LSRP, and non-meridian control points.


RESULTS
The skin stimulus-evoked electrical currents at BL 56 (36.4 +/- 1.4 microA), PC 6 (35.4 +/- 1.2), and CV 17 (33.1 +/- 1.4) were significantly higher than those in non-LSRP and non-meridian control positions (p < 0.01, n = 7). The currents were consistently increased after repeated stimulation along the skin as a function of time. Intravenous injections of L-arginine (3 mg/kg, 10 mg/kg, and 30 mg/kg) and 3-morpholinyl-sydnoneimine (SIN-1; 1 microg/kg, 3 microg/kg, and 10 microg/kg) produced dose-dependent increases in the currents (p < 0.05, n = 5-6), but currents were not altered by injections of D-arginine (3 mg/kg, 10 mg/kg, and 30 mg/kg). Stimulus-evoked increases in currents were blocked by intravenous injections of either N (G)-propyl-L-arginine (NPLA, 3 mg/kg), N-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg), or guanethidine (3 mg/kg), a noradrenergic blockade.


CONCLUSIONS
This is the first evidence showing that L-arginine-derived NO synthesis and noradrenergic transmission modify the skin electric conductance of LSRP. L-Arginine-derived NO synthesis appears to mediate noradrenergic function on skin sympathetic nerve activation, which contributes to low resistance characteristics of acupoints and meridians.
Department of Obstetrics and Gynecology, David Geffen School of Medicine, University of California, Los Angeles, Harbor-UCLA Medical Center, CA, USA.
Jia-Xu
JX
Chen
Sheng-Xing
SX
Ma
D015669:Acupuncture Points; D000704:Analysis of Variance; D000818:Animals; D015671:Electroacupuncture / Q000379:methods; D005712:Galvanic Skin Response; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014665:Vasodilator Agents / Q000378:metabolism*
D014665:Vasodilator Agents; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D009638:Norepinephrine