Autor(es): Aslani, Shilan ; Harb, Mazen R. ; Costa, Patrício Soares ; Almeida, O. F. X. ; Sousa, Nuno ; Palha, Joana Almeida
Data: 2014
Identificador Persistente: http://hdl.handle.net/1822/32854
Origem: RepositóriUM - Universidade do Minho
Projeto/bolsa: info:eu-repo/grantAgreement/FCT/5876-PPCDTI/111814/PT ;
Assunto(s): Behavioral test; Chronic mild stress; Depression model; Diurnal phase; Stress; Science & Technology
Chronic mild stress (CMS) protocols are widely used to create animal models of depression. Despite this, the inconsistencies in the reported effects may be indicative of crucial differences in methodology. Here, we considered the time of the diurnal cycle in which stressors are applied as a possible relevant temporal variable underlying the association between stress and behavior. Most laboratories test behavior during the light phase of the diurnal cycle, which corresponds to the animal's resting period. Here, rats stressed either in their resting (light phase) or active (dark phase) periods were behaviorally characterized in the light phase. When exposure to CMS occurred during the light phase of the day cycle, rats displayed signs of depressive and anxiety-related behaviors. This phenotype was not observed when CMS was applied during the dark (active) period. Interestingly, although no differences in spatial and reference memory were detected (Morris water maze) in animals in either stress period, those stressed in the light phase showed marked impairments in the probe test. These animals also showed significant dendritic atrophy in the hippocampal dentate granule neurons, with a decrease in the number of spines. Taken together, the observations reported demonstrate that the time in which stress is applied has differential effects on behavioral and neurostructural phenotypes.
Shilan Aslani and Mazen R. Harb were supported by EU Marie Curie Initial Training Fellowships from the NINA Project. Part of this work was supported by the Life and Health Sciences Research Institute (ICVS) and by FEDER funds through Operational program for competitivity factors-COMPETE and by national funds through FCT-Foundation for Science and Technology to project "PTDC/SAU-NSC/111814/2009."
