Adaptation of corticosterone-but not beta-endorphin-secretion to repeated blood sampling in rats

Lab Anim. 1999 Apr;33(2):185-91. doi: 10.1258/002367799780578309.


Effects of short-term repeated blood sampling on the secretion of corticosterone (CORT) and beta-endorphin (beta-END) were evaluated in male Wistar rats. Blood was drawn from the tail vein of conscious rats four times within 2 h both at the peak and trough period of the diurnal corticosterone secretion cycle. All rats were well accustomed to the procedure. The main findings were: (1) At both sampling intervals, CORT increased significantly in response to the first sampling and declined to baseline values in successive samples. (2) beta-END also increased significantly in response to the first sampling but remained elevated in successive samples. (3) Intensities of initial CORT and beta-END responses correlated positively with each other and with the baseline beta-END values. Feedback inhibition of CORT secretion with sustained elevation of beta-END titres suggests a moderate stress intensity of the repeated blood sampling procedures. In general, due to lack of short-term feedback inhibition, beta-END seems to reflect the effects of repeated administration of moderate intense stressors more closely than CORT.

MeSH terms

  • Animal Welfare*
  • Animals
  • Blood Specimen Collection / adverse effects
  • Blood Specimen Collection / veterinary*
  • Chromatography, High Pressure Liquid / veterinary
  • Corticosterone / blood
  • Corticosterone / metabolism*
  • Feedback
  • Male
  • Radioimmunoassay / veterinary
  • Rats / physiology
  • Rats / psychology*
  • Stress, Physiological / blood
  • Stress, Physiological / etiology
  • Stress, Physiological / veterinary*
  • Time Factors
  • beta-Endorphin / blood
  • beta-Endorphin / metabolism*


  • beta-Endorphin
  • Corticosterone