Study on the model for the vulnerability to stress using stress-induced c-fos mRNA expression as an index of stress response.

1996 Fiscal Year Final Research Report Summary

• Project/Area Number: 07807092
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Psychiatric science
• Research Institution: SAITAMA MEDICAL SHCOOL
• Principal Investigator: WATANABE Yoshifumi Saitama Medical School, assistant Professor, 医学部, 講師 (90182964)
• Co-Investigator(Kenkyū-buntansha): IIDA Atsufumi Saitama Medical School, Assistant, 医学部, 助手 (40255089) ; MINATOGAWA Yukiko Saitama Medical School, Assistant, 医学部, 助手 (60146272)
• Project Period (FY): 1995 – 1996
• Keywords: vulnerability to stress / c-fos mRNA / in situ hybridization / Wistar Kyoto rats / paraventricle nucleus / locus coeruleus / Corticosterone

Research Abstract

1.Strain comparison in c-fos mRNA expression induced by acute and repeated restraint stress.
Wistar Kyoto (WKY) rats and Wistar rats were stressed by 1h restraint stress daily for one, three, seven and fourteen days. In these rats, stress-induced c-fos mRNA expression in paraventricle nucleus (PVN) and locus coeruleus (LC) were measured by in situ hybridization assay.
To an acute restraint stress, WKY rats and Wistar rats showed similar c-fos mRNA expression in both PVN and LC.As reported before, Wistar rats showed substantial decrease in stress-induced c-fos mRNA expression in both PVN and LC on third stress day, and thereafter stress-induced c-fos mRNA expression decreased gradually. WKY rats, also, showed similar pattern of decrease in stress-induced c-fos mRNA expression in both PVN and LC by repeated restraint stress. Administration of imipramine, an antidepressant, for two weeks with repeated 1h restraint stress did not affect the decrement of stress-induced c-fos mRNA expression i n both PVN and LC in WKY rats.
These results suggest that WKY rats are not sensitive and vulnerable to stress.
2.Strain comparison in stress response of HPA axis and stress-induced anxiety.
Plasma corticosterone (CS) were measured during 2h restraint stress on first, third, sixth and thirteenth stress day in WKY rats and Wistar rats.
To an acute restraint stres, WKY rats showed higher peak CS level compared to Wistar rats. Wistar rats showed decrease in peak CS levels and other CS levels at 30min, 60min and 120min after the beginning of the stress from third stress day, and thereafter the decrement of CS levels were getting greater by thirteenth stress day, whereas WKY rats did not show the decrease in peak CS level by thirteenth stress day, and only CS levels at 120min after the beginning of the stress decreased from third stress day.
To measure the stress-induced anxiety, we measures the freezing time after fifteen minits footshock stress. Wistar rats showed reduction of the freezing time from fifth stress day, whereas WKY rats did not show any reduction of the freezing time by thirteenth stress day.
These results suggest the sensitivity and the vulnerability of WKY rats to stress.