Change of beta-endorphin concentration in rat brain after administration of indomethacin or carrageenin.
This study aimed to investigate the behavior of an endogenous beta-endorphin (beta-EP) in the brain after subcutaneous (s.c.) injection of carrageenin or intravenous (i.v.) injection of indomethacin (IDM). The carrageenin was injected into rat hind paw subcutaneously in order to evoke only a local nociceptive stimulus. The beta-EP concentration in the brain region was determined by radioimmunoassay at designated sampling times after the injection. It was observed that the beta-EP concentration in the midbrain declined from 2.8+/-0.3 at 1 h to 1.3+/-0.02 ng/mg protein at 9 h. After the s.c. injection of carrageenin, the beta-EP concentrations in the midbrain were found to be closely related to the nociceptive sensitivity which was determined by the Randall-Selitto test. On the other hand, a significant elevation of the beta-EP concentration was observed in the hypothalamus from 3 h until 5 h compared with that of control. IDM was injected into rats at doses of 2.9, 5.8 and 8.6 mg/kg via the femoral vein. After i.v. administration of IDM, the beta-EP increased in the hypothalamus, medulla oblongata, and midbrain, depending on the doses used. The value of hypothalamic beta-EP concentration was two times higher than that of carrageenin. We found that nociceptive stimuli and IDM brought a change in the beta-EP concentration in the brain of rats.
Suganuma
T
T
Department of Pharmaceutical Science, College of Pharmacy, Nihon University, Chiba, Japan.
Suzuki
T
T
Oshimi
M
M
Hanano
M
M
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002351:Carrageenan / Q000494:pharmacology*; D005260:Female; D007213:Indomethacin / Q000494:pharmacology*; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D010147:Pain Measurement; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D001615:beta-Endorphin / Q000378:metabolism*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D001615:beta-Endorphin; D002351:Carrageenan; D007213:Indomethacin