1987 Fiscal Year Final Research Report Summary

Neuropsychological study on stress-induced analgesia

Research Project

Project/Area Number	60450018
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	Psychology
Research Institution	Osaka City University
Principal Investigator	UMEMOTO Mamoru Faculty of Letters, Osaka City Univiersity, 文学部, 教授 (60101284)
Project Period (FY)	1985 – 1987
Keywords	Stress-induced alalgesia / Hot-plate method / Morphine / ラット
Research Abstract	Rat pups were daily given footshock, just putting in a footshock apparatus or no handling from birth to twenty-one days of age. They were reared with on manipulation afterwards. After maturation, they were assesed for hot-plate paw-licking latency, morphine induced analgesia and opioid receptor binding assaya. In footshocked animals, a significant increase was found in paw-licking latency and in antinociceptive dffect of morphine(1.25, 2.5, and 5.0 mg-kg) compared with other two controls. The analgesic effect of morphine was antagonized with pretreatment of naloxone(2.0 mg/kg). No significant difference was found in binding assay( Bmax and kd for both ( Inaloxone and ( ) D-ala,D-leu-enkephalin between three groups). These results suggest thatexposure to footshock in preweanling perios has the long term effecton the sensitivity of rats to painful event, decreasing the pain sensitivity, probably through chronic fundtional changes in endogeneous opiod systemat presynaptic level rather than in postsynaptic opioid receptor activity.