The behavioral effects of enriched housing are not altered by serotonin depletion but enrichment alters hippocampal neurochemistry.
To assess a possible role for serotonin in the mediation of the behavioral changes induced by enriched housing conditions (EC), adult female Long-Evans rats sustaining a serotonin depletion (150 microg of 5,7-dihydroxytryptamine, icv) and sham-operated rats were housed postoperatively for 30 days in enriched (12 rats/large cage containing various objects) or standard housing conditions (2 rats/standard laboratory cage). Thereafter, anxiety responses (elevated plus-maze), locomotor activity (in the home-cage), sensori-motor capabilities (beam-walking task), and spatial memory (eight-arm radial maze) were assessed. Monoamine levels were subsequently measured in the frontoparietal cortex and the hippocampus. Overall, EC reduced anxiety-related responses, enhanced sensori-motor performance and improved the memory span in the initial stage of the spatial memory task. Despite a substantial reduction of serotonergic markers in the hippocampus (82%) and the cortex (74%), these positive effects of EC were not altered by the lesion. EC reduced the serotonin levels in the ventral hippocampus (particularly in unlesioned rats: -23%), increased serotonin turnover in the entire hippocampus (particularly in lesioned rats: +36%) and augmented the norepinephrine levels in the dorsal hippocampus (+68% in unlesioned and +49% in lesioned rats); no such alterations were found in the frontoparietal cortex. Our data suggest that an intact serotonergic system is not a prerequisite for the induction of positive behavioral effects by EC. The neurochemical changes found in the hippocampus of EC rats, however, show that the monoaminergic innervation of the hippocampus is a target of EC.
Galani
Rodrigue
R
LINC, UMR 7191 CNRS, Université Louis Pasteur, IFR 37, GDR 2905 du CNRS, Strasbourg, France. rodrigue.galani@psycho-ulp.u-strasbg.fr <rodrigue.galani@psycho-ulp.u-strasbg.fr>
Berthel
Marie-Camille
MC
Lazarus
Christine
C
Majchrzak
Monique
M
Barbelivien
Alexandra
A
Kelche
Christian
C
Cassel
Jean-Christophe
JC
D000704:Analysis of Variance; D000818:Animals; D001007:Anxiety / Q000378:metabolism; D004298:Dopamine / Q000502:physiology; D004777:Environment; D005106:Exploratory Behavior / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism*; D006799:Housing, Animal; D018782:Maze Learning / Q000502:physiology*; D008570:Memory, Short-Term / Q000502:physiology; D009043:Motor Activity / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism; D010296:Parietal Lobe / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D045442:Rotarod Performance Test; D012701:Serotonin / Q000172:deficiency / Q000502:physiology*; D018709:Statistics, Nonparametric
D012701:Serotonin; D004298:Dopamine; D009638:Norepinephrine