title: Social interaction with rat exposed to constant light during lactation prevents depressive-like behavior induced by constant light in adulthood.
abstract: Circadian rhythm disruptions are often observed in depressed patients, and changes in the light/dark cycle promote depressive-like behavior in animal models. Prolonged exposure to constant light (LL) is known to lead to arrhythmicity of circadian locomotor activity and depressive-like behavior in rats. Interestingly, neonatal exposure to LL prevents both arrhythmicity and depressive behavior in adulthood. Arrhythmic rats under LL conditions that cohabitate with a rhythmic rat exhibit improvement in circadian rhythms. We tested whether such cohabitation also protects against LL-induced depressive-like behavior. Wistar rats were assigned to conditions of either neonatal constant light (neonatal-LL) on postnatal days 10-22 or a regular light/dark cycle (neonatal-LD). On day 45, the animals were assigned to three possible pair combinations. After a baseline sucrose preference test, half of the pairs were placed under LL conditions. Weekly sucrose preference tests were conducted to evaluate depressive-like behavior. The animals were isolated by an aluminum wall on the test day. At week 2 of LL, sucrose preference was reduced in neonatal-LD/neonatal-LD pairs of animals. At week 5, neonatal-LD/neonatal-LD pairs exhibited anhedonic-like behavior, but the pairs with at least one neonatal-LL rat did not. The LL cycle was returned to an LD cycle, and the neonatal-LD/neonatal-LD pairs exhibited a restoration of sucrose preference 2 weeks later. We conclude that social interaction can prevent depressive-like behavior induced by circadian rhythm disruption as long as one of the animals is more prone to present a strong rhythm.
authors.affiliation: Departamento de Farmacologia, Universidade Federal do Paraná Cel. Francisco H. dos Santos, Centro Politécnico, Curitiba, Paraná 81530-900, Brazil. Electronic address: brunojm@ymail.com.
authors.forename: Bruno Jacson
authors.initials: BJ
authors.lastname: Martynhak
authors.affiliation: Departamento de Farmacologia, Universidade Federal do Paraná Cel. Francisco H. dos Santos, Centro Politécnico, Curitiba, Paraná 81530-900, Brazil.
authors.forename: Luiz Kae Sales
authors.initials: LK
authors.lastname: Kanazawa
authors.affiliation: Departamento de Farmacologia, Universidade Federal do Paraná Cel. Francisco H. dos Santos, Centro Politécnico, Curitiba, Paraná 81530-900, Brazil.
authors.forename: Guilherme
authors.initials: G
authors.lastname: Messias do Nascimento
authors.affiliation: Departamento de Farmacologia, Universidade Federal do Paraná Cel. Francisco H. dos Santos, Centro Politécnico, Curitiba, Paraná 81530-900, Brazil.
authors.forename: Roberto
authors.initials: R
authors.lastname: Andreatini
mesh_terms: D000367:Age Factors; D000818:Animals; D002940:Circadian Rhythm; D003863:Depression / Q000517:prevention & control / Q000523:psychology*; D005260:Female; D007774:Lactation; D008027:Light; D008297:Male; D017208:Rats, Wistar; D012919:Social Behavior
keywords: Anhedonia; Circadian rhythms; Constant light; Depression; Depressive-like; Neonatal