Copyright © 2009 The Association for the Study of Animal
Behaviour Published by Elsevier Ltd.
Progesterone can enhance consolidation and/or performance in
spatial, object and working memory tasks in Long–Evans rats
Cheryl A. Fryea, b, c, d, , , Danielle C. Llanezaa and Alicia A.
Walfa
Department of Psychology, The University at Albany-SUNY, NY,
U.S.A. Department of Biology, The University at Albany-SUNY, NY,
U.S.A. Center for Neuroscience, The University at Albany-SUNY,
NY, U.S.A. Center for Life Sciences Research, The University at
Albany-SUNY, NY, U.S.A.
Received 11 June 2008; revised 7 August 2008; accepted 14 April
2009. MS. number: A08-00396R. Available online 10 June 2009.
Progesterone has a ubiquitous role in reproduction and fitness
and may influence cognitive performance. We examined the effects
of administration of progesterone (a regimen that facilitates
sexual behaviour) on consolidation of complex information in
Long–Evans rats, Rattus norvegicus, that may be relevant for
social engagement. We also examined the effects of subcutaneous
progesterone administration (4 mg/kg versus oil vehicle placebo)
on memory of ovariectomized rats during various cognitive tasks.
Ovariectomized rats that received progesterone, versus the
vehicle, immediately post-training were better able to find a
hidden platform in the water maze. In a recognition task, rats
that received progesterone spent more time in the novel arm of
the Y-maze task than rats that received the vehicle.
Ovariectomized rats that received progesterone immediately after
training spent significantly more time exploring a novel object
(compared to a familiar object) than did vehicle-administered
rats. When socially relevant stimuli (i.e. objects with the scent
of familiar or novel conspecifics) were used in the social
cognition task, ovariectomized rats that received progesterone
spent more time exploring the object with the novel conspecifics'
scent than did vehicle-administered rats. Pairing of
progesterone, but not the vehicle, conditioned a place preference
to the originally nonpreferred side of the conditioning chamber.
We found no significant differences in motor activity measures in
these tasks due to progesterone treatment. These results suggest
that progesterone's effects to improve cognitive processes with
nonsocial and socially relevant stimuli, as well as have
reinforcing effects, may underlie some of its salient effects on
reproduction-related behaviours.
