title: Neonatal exposure to constant light prevents anhedonia-like behavior induced by constant light exposure in adulthood.
abstract: Depressive episodes are associated with disturbances in circadian rhythms, and constant illumination has been reported to induce depressive-like behavior in rodents. Rats kept in constant darkness express the endogenous circadian rhythm, and most animals under constant light conditions lose circadian locomotor rhythmicity. Exposure to constant light in rats during lactation was reported to prevent this loss of circadian rhythm in adulthood. Thus, the aim of the present study was to verify whether exposure to constant light during lactation prevents anhedonia-like behavior induced by constant light in adult rats. In experiment 1, we replicated the anhedonia-like effects of constant light in adult male rats. We showed that this effect is reversed by imipramine treatment in the drinking water. In experiment 2, we subjected rats to constant darkness (neonatal-DD), constant light (neonatal-LL) or to normal light/dark cycle (neonatal-LD) during the neonatal phase and evaluated them after constant light exposure in adulthood. The group exposed to constant light during the neonatal phase did not reduce their sucrose preference and exhibited greater locomotor activity than the other groups. The neonatal-DD group exhibited decreased sucrose preference earlier than controls and had higher serum corticosterone concentrations. Prevention of arrhythymicity might protect neonatal-LL rats from anhedonia-like behavior induced by constant light, whereas constant darkness during the neonatal phase rendered the neonatal-DD group more susceptible to depressive-like behavior. These results corroborate with the literature data indicating that circadian disruption may contribute in mood disorders and that early life stress can influence stress responsivity in adulthood.
authors.affiliation: Universidade Federal do Paraná, Departamento de Farmacologia, Cel. Francisco H. dos Santos, Centro Politécnico, 81530-900 - Curitiba, Paraná, PR, Brazil. brunojm@ymail.com
authors.forename: Bruno J
authors.initials: BJ
authors.lastname: Martynhak
authors.forename: Diego
authors.initials: D
authors.lastname: Correia
authors.forename: Lívia H
authors.initials: LH
authors.lastname: Morais
authors.forename: Paula
authors.initials: P
authors.lastname: Araujo
authors.forename: Monica L
authors.initials: ML
authors.lastname: Andersen
authors.forename: Marcelo M S
authors.initials: MM
authors.lastname: Lima
authors.forename: Fernando M
authors.initials: FM
authors.lastname: Louzada
authors.forename: Roberto
authors.initials: R
authors.lastname: Andreatini
mesh_terms: D000342:Affective Symptoms / Q000097:blood / Q000188:drug therapy / Q000209:etiology* / Q000517:prevention & control*; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D000929:Antidepressive Agents, Tricyclic / Q000627:therapeutic use; D001522:Behavior, Animal / Q000187:drug effects; D003345:Corticosterone / Q000097:blood; D004195:Disease Models, Animal; D005260:Female; D005518:Food Preferences / Q000502:physiology*; D007099:Imipramine / Q000627:therapeutic use; D008027:Light / Q000009:adverse effects*; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000929:Antidepressive Agents, Tricyclic; D007099:Imipramine; D003345:Corticosterone