Effects of opioids on the heat stimulus-evoked substance P release and thermal edema in the rat hind paw.
We examined the effect of opioids on the heat stimulus-evoked release of substance P (SP) into the subcutaneous space and the formation of edema in the rat hind paw. Immersion of the rat hind paw for 30 min into hot water adjusted to 47 degrees C led to a marked increase in the release of SP into the subcutaneous perfusate with the formation of thermal edema. Intra-arterial infusion of morphine (10-100 mumol/kg) or ethylketocyclazocine (30-100 mumol/kg) inhibited dose dependently the heat stimulus-evoked increase in SP release and the thermal edema and the inhibitory effects were antagonized by pretreatment with N-methyl levallorphan (10 mg/kg i.p.) and Win 44,441-3 (10 mg/kg i.p.). The heat stimulus-evoked release of SP was reduced significantly during the intra-arterial infusion of [D-Ala2,Met5] enkephalinamide (100 mumol/kg). These results suggest that the opioid-induced inhibition of heat-induced edema could result from inhibition of the release of SP from peripheral sensory nerve endings.
Yonehara
N
N
Department of Pharmacology, Faculty of Dentistry, Osaka University, Japan.
Imai
Y
Y
Inoki
R
R
D000818:Animals; D004487:Edema / Q000378:metabolism*; D005528:Foot; D006358:Hot Temperature; D007269:Injections, Intra-Arterial; D008297:Male; D009294:Narcotics / Q000494:pharmacology*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D013373:Substance P / Q000378:metabolism*
D009294:Narcotics; D013373:Substance P