title: A detailed analysis of open-field habituation and behavioral and neurochemical antidepressant-like effects in postweaning enriched rats.
abstract: Our previous work has shown that male Sprague-Dawley rats reared in social isolation, standard housing and environmental enrichment differ in their spontaneous open-field activity and in some neurobehavioral depressive-like parameters. Here, we extended this evidence by using a shorter postweaning rearing period (1 month) and including additional evaluations. First, in order to obtain a better characterization of the exploratory strategies among rearing conditions we analyzed in detail the spontaneous activity at the first minute and during the 10-min session. Second, we asked whether the changes in open-field activity were related with basal anxiety levels in the elevated plus-maze. Third, behavior in the forced-swimming test was analyzed and afterward, the tissue levels of hippocampal norepinephrine and serotonin were assessed. The possible relationship between neurotransmitters and forced-swimming behavior were explored through correlation analyses. We found that rearing conditions (i) differed on locomotor habituation and on sensory-motor exploration at the first minute and during the 10-min session without modifying the plus-maze behavior; (ii) affected differentially the grooming time, its sequential components, and the relationship between grooming and locomotor parameters; (iii) modified forced-swimming behavior and the hippocampal concentration of norepinephrine, serotonin, and its turnover; and (iv) produced different correlation patterns between both neurotransmitters and forced-swimming behaviors. Overall, environmental enrichment accelerated open-field habituation and led to behavioral and neurochemical antidepressant-like effects. In contract, isolation rearing strongly impaired habituation and simple information processing, but showed marginal effects on depressive-like behavior and on hippocampal neurochemistry. The current results suggest that differential rearing is not only a useful procedure to study behavioral plasticity or rigidity in response to early experience, but also to modeling some developmental protective or risk factors underlying depressive disorders.
authors.affiliation: Neuroscience Research Program, University of Costa Rica, Costa Rica.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Brenes
authors.forename: Michael
authors.initials: M
authors.lastname: Padilla
authors.forename: Jaime
authors.initials: J
authors.lastname: Fornaguera
mesh_terms: D000223:Adaptation, Psychological; D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D003423:Critical Period, Psychological; D003863:Depression / Q000503:physiopathology / Q000523:psychology*; D004195:Disease Models, Animal; D004777:Environment; D004924:Escape Reaction / Q000502:physiology; D005106:Exploratory Behavior / Q000502:physiology*; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D006624:Hippocampus / Q000378:metabolism; D006799:Housing, Animal; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism; D012931:Social Environment; D012934:Social Isolation; D013037:Spatial Behavior / Q000502:physiology*; D018709:Statistics, Nonparametric
chemical_list: D012701:Serotonin; D009638:Norepinephrine