title: Reproductive experience alters anxiety-like behavior in the female rat.
abstract: Reproductive experience (i.e. pregnancy and lactation) results in significant alterations in subsequent hormone levels in female rats. Several studies have demonstrated that circulating hormones can significantly affect anxiety-like behavior. Thus, the purpose of the present study was to determine whether reproductive experience induces alterations in anxiety-like behaviors in cycling female rats and in older, reproductively senescent rats. In Experiment 1, the elevated plus maze (EPM) was used to test young cycling (6-8 weeks post-weaning) and middle-aged (32-36 weeks post-weaning) primiparous rats and their age-matched nulliparous counterparts for anxiety-like responses. In Experiment 2, activity in the open field was used as an additional measure of anxiety-like behavior in young (proestrus) and middle-aged (constant estrus) primiparous and nulliparous rats. For Experiment 3, EPM testing was conducted in separate groups of young and middle-aged animals tested two weeks after ovariectomy. The results revealed that during proestrus, primiparous animals exhibited fewer anxiety-like behaviors on the EPM compared to nulliparous controls. In middle-aged animals, however, parity was associated with increased anxiety-like behavior. In the open field, young, non-lactating primiparous animals again exhibited fewer anxiety-like behaviors compared to nulliparous controls, an effect that was reversed in middle-aged animals. Effects of reproductive experience on the EPM in both age groups were eliminated by ovariectomy. Overall, the findings indicate that reproductive experience significantly alters anxiety-like behavior, effects that are influenced by the endocrine status and/or age of the female.
authors.affiliation: Department of Biomedical Sciences, Tufts University, Cummings School of Veterinary Medicine, 200 Westboro Road, North Grafton, MA 01536, USA. elizabeth.byrnes@tufts.edu
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Byrnes
authors.forename: Robert S
authors.initials: RS
authors.lastname: Bridges
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D001007:Anxiety / Q000097:blood*; D004958:Estradiol / Q000097:blood; D030762:Estrous Cycle / Q000097:blood*; D005106:Exploratory Behavior / Q000502:physiology*; D005260:Female; D020073:Gravidity / Q000502:physiology*; D010298:Parity / Q000502:physiology*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D011388:Prolactin / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D011374:Progesterone; D004958:Estradiol; D011388:Prolactin