ANTIDEPRESSANT-LIKE EFFECTS OF ENRICHED ENVIRONMENT ARE NOT DUE TO AN INCREMENT IN NEUROGENESIS: RESULTS FROM ANIMALS EXPOSED TO AN EXPERIMENTAL MODEL OF DEPRESSION

SIFONIOS; TRINCHERO M; REINÉS A; CERESETO M; FERRERO A; WIKINSKI S

Munich, Alemania

Congreso; XXVI CINP Congress; 2008

Collegium Internationale Neuropsychopharmacologicum

Exposure to enriched environment (EE) has been shown to promote antidepressant-like effects in naïve animals, but its action in animals exposed to an experimental model of depression remains unknown. Our work was aimed to investigate the behavioral effect of EE in animals exposed to the learned helplessness (LH) paradigm, as well as in structural and synaptic markers previously shown to be decreased in this depressive-like condition: the core subunit of the cytoskeletal neurofilaments (NFL), the proteins PSD-95 and synaptophysin (SYN). Potential relationships between EE-induced changes and neurogenesis were also assessed. Male rats, in which LH behavior was induced by exposure to inescapable stress, were kept in the EE, a special cage provided with ropes, a running wheel and different toys (LHEE). Two control groups were employed, LH animals housed in standard cages (LH) and animals not exposed to inescapable stress (C). Twenty-one days later, depressive-like behavior (escape latency in an active task), NFL, PSD-95 and SYN immunolabeling were quantified in CA3 and dentate gyrus of hippocampus. EE reversed the behavioral despair (P<0.05 versus LH, P > 0.05 versus C) and the decrements in NFL (P < 0.05 versus LH, P > 0.05 versus C) and in PSD-95 (p < 0.05 versus LH, P > 0.05 versus C) in hippocampus. No statistically significant effects on SYN were detected. A double immunofluorescence BrdU/βTubulin III revealed that EE fails to promote an increment in the neuronal survival in LHEE animals, while, as previously shown by other authors, C animals exposed to enriched environment exhibit a significant increment in double-stained cells. Our results support the conclusion that EE mimics antidepressant actions on behavioral, cytoskeletal and synaptic parameters, but that these properties are not related to an increment in neurogenesis.  Supporting grants: ANPCyT PICT-2005-31953, UBA M013, CONICET PIP 5870.