1992 Fiscal Year Final Research Report Summary
Psychophysiological studies on function of brain reward system in aged animals.
| Project/Area Number |
03451013
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Psychology
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| Research Institution | University of Tsukuba |
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Principal Investigator |
IWASAKI Tsuneo Institute of Psychology, University of Tsukuba, Professor, 心理学系, 教授 (70092509)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAHARA Daiichiro Department of Psychology, Nagoya University College of Medical Technology, Assoc, 医療技術短期大学部, 助教授 (80128389)
FURUKAWA Satoshi Institute of Psychology, University of Tsukuba, Research Associate, 心理学系, 助手 (70229110)
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| Project Period (FY) |
1991 – 1992
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| Keywords | aging / brain microdialysis / brain self-stimulation / brain reward system / rat |
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| Research Abstract |
In order to investigate the changes of brain reward system with aging, brain monoamines and their metabolites of rats performing intracranial self-stimulation (ICSS) had been measured using in vivo microdialysis. Young (4-6 months old) and aged (20-22 months old) F344 rats were implanted with ICSS electrodes in the lateral hypothalamus and with cannula for dialysis probes in the nucleus accumbens. Four to 7 days after operation, ICSS training in an operant chamber began, and continued until the animal's stable lever-pressing response to obtain 0.3sec electrical stimulation (100Hz pulse) which did not induce motor disturbance had been established. On the next day we conducted the microdialysis experiment, in which dialysis samples were collected during ICSS session (1h) as well as pre-(1h) and post-ICSS (2h) sessions.
In both aged and young rats, dopamine (DA) release increased by 50% during ICSS session compared with that of baseline level. On the other hand, DOPAC, an metabolite of DA, increased up to 200% of baseline level in young rats, while such a significant increase was not detected in aged rats. Raising the potassium concentration of the perfusate (potassium loading) facilitated DA release in aged rats. Degree of decrease in DA metabolites after potassium loading was smaller in aged rats, indicating the decrease of DA uptake in those rats. Results suggest that (1) ICSS behavior does not show clear change with aging, and (2) DA uptake function in nerve terminals may change with aging. Further research is needed to clarify the changes of the number of dopaminergic terminals and their function in aged animals.
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