[Effects of morphine on cutaneous blood flow and substance P release evoked by electric stimulation of rat sciatic nerve].
Electric stimulation of the rat sciatic nerve containing sensory afferent fibers produced an increase in cutaneous blood flow. Morphine (10, 30 mumol.kg-1 ia infusion) inhibited the electric stimulation-induced increase of the cutaneous blood flow velocity, and its effect was antagonized by naloxone (2 mg.kg-1 ip). In order to investigate the cause of this effect, we determined immunoreactive substance P (iSP) levels in the sc perfusate of hind paw. We found that electric stimulation of the sciatic nerve led to a significant increase of iSP release into the sc perfusate. Morphine (30 mumol.kg-1 ia infusion) inhibited the electrical stimulation-induced release of iSP, and this effect was completely antagonized by naloxone (2 mg.kg-1 ip). These result suggest that morphine-induced inhibition of the electrical stimulation-evoked increase in cutaneous blood flow could result from inhibition of the release of SP from peripheral sensory nerve endings.
Chen
J Q
JQ
Department of Pharmacology, Faculty of Dentistry, Osaka University, Japan.
Yonehara
N
N
Imai
Y
Y
Xu
W J
WJ
Inoki
R
R
D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects; D004558:Electric Stimulation; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012584:Sciatic Nerve / Q000502:physiology*; D012867:Skin / Q000098:blood supply*; D013373:Substance P / Q000378:metabolism*
D013373:Substance P; D009270:Naloxone; D009020:Morphine