EFFECTS OF DESCENDING INHIBITORY SYSTEM ON SPINAL PAIN TRANSMISSION IN AGED RATS

2003 Fiscal Year Final Research Report Summary

• Project/Area Number: 14580795
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 神経・脳内生理学
• Research Institution: Tokyo Metropolitan Foundation for Research on Aging and Promotion of Human Welfare
• Principal Investigator: KANDA Kenro TOKYO METROPOLITAN FOUNDATION FOR RESEARCH ON AGING AND PROMOTION OF HUMAN WELFARE, TOKYO METROPOLITAN INSTITUTE OF GERONTOLOGY MOTOR AND AUTONOMIC NERVOUS SYSTEM INTERGRATION RESEARCH GROUP, LEADER (SENIOR SCIENTIST), 東京都老人総合研究所・運動・自律機能相関研究グループ, 参事研究員 (50009635)
• Project Period (FY): 2002 – 2003
• Keywords: PAIN / AGING / PLASTICITY / DESCENDING INHIBITORY SYSTEM

Research Abstract

In the present experiments, the wind-up phenomenon of the flexor reflex was investigated in young (4-to 6-month-old), middle-aged (9-to 13-month-old) and aged (29-to 32-month-old) rats under halothane anesthesia. The duration of C-fiber activated changes, which produce the wind-up phenomenon, was evaluated by the decay time constant parameter. The mean value of this time constant was significantly longer in the aged rats (9.2±3.2 s) than in the young rats (5.2±3.0 s). Spinal transection elongates the time constant in young rats (5.2 s to 10.6 s), but not in aged rats (9.2 to 8.1 s). These findings indicate that at least one cause for a longer decay time constant in the aged rats is due to a deficiency of the descending inhibitory system. The results suggest that plastic change in the nociceptive system in the aged rats is more easily induced compared to young and middle-aged rats. Fluvoxamine may improve this impairment.