title: Announced reward counteracts the effects of chronic social stress on anticipatory behavior and hippocampal synaptic plasticity in rats.
abstract: Chronic stress causes insensitivity to rewards (anhedonia) in rats, reflected by the absence of anticipatory behavior for a sucrose-reward, which can be reversed by antidepressant treatment or repeated announced transfer to an enriched cage. It was, however, not clear whether the highly rewarding properties of the enriched cage alone caused this reversal or whether the anticipation of this reward as such had an additional effect. Therefore, the present study compared the consequences of the announcement of a reward to the mere effect of a reward alone with respect to their efficacy to counteract the consequences of chronic stress. Two forms of synaptic plasticity, long-term potentiation and long-term depression were investigated in area CA1 of the hippocampus. This was done in socially stressed rats (induced by defeat and subsequent long-term individual housing), socially stressed rats that received a reward (short-term enriched housing) and socially stressed rats to which this reward was announced by means of a stimulus that was repeatedly paired to the reward. The results were compared to corresponding control rats. We show that announcement of enriched housing appeared to have had an additional effect compared to the enriched housing per se as indicated by a significant higher amount of LTP. In conclusion, announced short-term enriched housing has a high and long-lasting counteracting efficacy on stress-induced alterations of hippocampal synaptic plasticity. This information is important for counteracting the consequences of chronic stress in both human and captive rats.
authors.affiliation: Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Centre Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands. amerha@agu.edu.bh
authors.forename: Amer
authors.initials: A
authors.lastname: Kamal
authors.forename: Johanneke E
authors.initials: JE
authors.lastname: Van der Harst
authors.forename: Chantal M
authors.initials: CM
authors.lastname: Kapteijn
authors.forename: Annemarie J M
authors.initials: AJ
authors.lastname: Baars
authors.forename: Berry M
authors.initials: BM
authors.lastname: Spruijt
authors.forename: Geert M J
authors.initials: GM
authors.lastname: Ramakers
mesh_terms: D000818:Animals; D056547:CA1 Region, Hippocampal / Q000503:physiopathology*; D002908:Chronic Disease; D004291:Dominance-Subordination; D019706:Excitatory Postsynaptic Potentials; D006799:Housing, Animal; D066298:In Vitro Techniques; D017774:Long-Term Potentiation; D036881:Long-Term Synaptic Depression; D008297:Male; D009473:Neuronal Plasticity; D051381:Rats; D017208:Rats, Wistar; D012201:Reward; D012919:Social Behavior; D012934:Social Isolation; D013315:Stress, Psychological / Q000503:physiopathology* / Q000523:psychology; D013569:Synapses / Q000502:physiology*; D013997:Time Factors