Related Experiment Video
Updated: May 23, 2026

09:07
Protocol for Studying Extinction of Conditioned Fear in Naturally Cycling Female Rats
Published on: February 23, 2015
Infradian fluctuations in serum testosterone levels in male laboratory rats
1Institute of Human Morphology, Russian Academy of Medical Sciences, Moscow, Russia. diatrom@inbox.ru
Bulletin of Experimental Biology and Medicine
|March 31, 2012
Abstract:
The dynamics of serum testosterone was studied in laboratory male rats kept separately from females. Infradian rhythm of changes in testosterone level equal to 4 days and ultradian (within 24 h) periods equal to 160 and 480 min were detected. The maximum serum level of testosterone in male rats was synchronized with the greatest number of estrous females.

