[The role of substance P and somatostatin in acupuncture and moxibustion-induced postsynaptic inhibition].
OBJECTIVE
Our previous work indicated that acupuncture and moxibustion (heating acupoints with a special lamp) could produce inhibitory effects on the tail flick reflex and the nociceptive response of dorsal horn neurons. In the present study the role of somatostatin (SS) and substance P (SP) in acupuncture and moxibustion-induced postsynaptic inhibition was further investigated.


METHODS
The experiments were performed on male adult Wistar rats. The antidromic action potential (AAP) induced by cervical cord stimulation was extracellulary recorded at lumbar cord (L3-4). The latency of AAP was used to represent the excitability of postsynaptic projecting neurons. The effects of acupuncture (0.5 ms, 3.3 Hz, 2 mA) for five minutes or moxibustion (the temperature up to 45-46 degrees C) for six minutes at Huantiao points on the latency of AAP were observed. And then the effects of topical administration of SS or SP antiserum on either acupuncture or moxibustion-induced postsynaptic inhibition were observed.


RESULTS
The latency of AAP was markedly prolonged by acupuncture and moxibustion. The maximal prolongation was 0.196 +/- 0.071 ms (n = 12, P < 0.02) and 0.176 +/- 0.062 ms (n = 11, P < 0.02) respectively. After topical administration of SS antiserum (1:40, 10 microliters), the latency of AAP was slightly prolonged by either acupuncture or moxibustion. The maximal prolongation (0.041 +/- 0.029 ms and 0.016 +/- 0.020 ms) was significantly reduced by SS antiserum (P < 0.05). While pretreated with SP antiserum, the latency was still prolonged by moxibustion (0.142 +/- 0.067 ms), but not by acupuncture (-0.003 +/- 0.046 ms).


CONCLUSIONS
It is referred that postsynaptic inhibition may be involved in both acupuncture analgesia and moxibustion analgesia. The former is predominately mediated by SP and partially by SS, while the latter mainly by SS but not by SP.
Zhu
L X
LX
Institute of Acupuncture and moxibustion, China Academy of Traditional Chinese Medicine, Beijing.
Li
C Y
CY
Ji
C F
CF
Yang
B
B
Li
W M
WM
D000200:Action Potentials; D015667:Acupuncture Analgesia; D000818:Animals; D015671:Electroacupuncture; D005071:Evoked Potentials / Q000502:physiology; D008297:Male; D009071:Moxibustion; D009619:Nociceptors / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013004:Somatostatin / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology; D013373:Substance P / Q000502:physiology*; D013569:Synapses / Q000502:physiology*
D013373:Substance P; D013004:Somatostatin