Social recognition in ovariectomized and estradiol-treated female rats.

The behavioral phenomenon of social recognition has been extensively investigated in male rats. The present paper provides an insight into the recognition capacity of female rats studied throughout a sequence of hormonal states: after ovariectomy, after estradiol treatment, and several weeks after the termination of estradiol therapy. Investigatory behavior of the female oriented toward a juvenile male, 22-24 days old, was recorded during the 5-min exposure period. Reexposure was performed 30 or 120 min after the initial exposure. Reduction of the investigation time during reexposure to the same juvenile was used as a recognition criterion. It was found that: (a) Three weeks after ovariectomy, the investigation time of females was decreased upon reexposure to the same juvenile at 30 min. At this time point the investigation time of females reexposed to a novel juvenile was similar to that observed during the initial exposure. Both the same as well as a novel juvenile were thoroughly reinvestigated by females when 120 min elapsed between exposures. (b) Three weeks later, administration of estradiol dipropionate to ovariectomized animals (always 100 micrograms per animal at Days 10 and 3 before the testing) resulted in reduced investigation time during reexposure to the same juvenile at both 30 and 120 min. (c) Original time-response relations in the investigation appeared 6 weeks after the termination of estradiol treatment. These findings suggest that the presence of estradiol may be crucial for female recognition of males 120 min after a brief encounter.(ABSTRACT TRUNCATED AT 250 WORDS)