Effects of prenatal exposure to a mild chronic variable stress on body weight, preweaning mortality and rat behavior

Abstract

Early stimulation has been shown to produce long-lasting effects in many species. Prenatal exposure to some strong stressors may affect development of the nervous system leading to behavioral impairment in adult life. The purpose of the present work was to study the postnatal harmful effects of exposure to variable mild stresses in rats during pregnancy. Female Holtzman rats were submitted daily to one session of a chronic variable stress (CVS) during pregnancy (prenatal stress; PS group). Control pregnant rats (C group) were undisturbed. The pups of PS and C dams were weighed and separated into two groups 48 h after delivery. One group was maintained with their own dams (PS group, N = 70; C group, N = 36) while the other PS pups were cross-fostered with C dams (PSF group, N = 47) and the other C pups were cross-fostered with PS dams (CF group, N = 58). Pups were undisturbed until weaning (postnatal day 28). The male offspring underwent motor activity tests (day 28), enriched environment tests (day 37) and social interaction tests (day 42) in an animal activity monitor. Body weight was recorded on days 2, 28 and 60. The PS pups showed lower birth weight than C pups (Duncans test, P<0.05). The PS pups suckling with their stressed mothers displayed greater preweaning mortality (C: 23%, PS: 60%; c 2 test, P<0.05) and lower body weight than controls at days 28 and 60 (Duncans test, P<0.05 and P<0.01, respectively). The PS, PSF and CF groups showed lower motor activity scores than controls when tested at day 28 (Duncans test, P<0.01 for PS group and P<0.05 for CF and PSF groups). In the enriched environment test performed on day 37, between-group differences in total motor activity were not detected; however, the PS, CF and PSF groups displayed less exploration time than controls (Duncans test, P<0.05). Only the PS group showed impaired motor activity and impaired social behavior at day 42 (Duncans test, P<0.05). In fact, CVS treatment during gestation plus suckling with a previously stressed mother caused long-lasting physical and behavioral changes in rats. Cross-fostering PS-exposed pups to a dam which was not submitted to stress counteracted most of the harmful effects of the treatment. It is probable that prenatal stress plus suckling from a previously stressed mother can induce long-lasting changes in the neurotransmitter systems involved in emotional regulation. Further experiments using neurochemical and pharmacological approaches would be interesting in this model. Correspondence

Influência da exposição a fumaça lateral do cigarro sobre o ganho de peso e o consumo alimentar de ratas gestantes: análise do peso e do comprimento dos filhotes ao nascimento

“…Modelos de estresse aplicados a ratas gestantes têm mostrado comprometimento do peso dos filhotes 36,37 , com variação no comprometimento do peso materno [36][37][38] . A restrição alimentar em ratas gestantes não foi capaz de prejudicar o peso dos filhotes tanto quanto a exposição tabágica 32 .…”

Gestational Nicotine Exposure Attenuates Nicotine-Stimulated Dopamine Release in the Nucleus Accumbens Shell of Adolescent Lewis Rats

“…A standard model of cross-fostering was used (Ribary and Lichtensteiger, 1989;Cabrera et al, 1999;Nyirenda et al, 2001). Cross-fostering was conducted to acquire the following experimental groups: 1) "control group", in which pups from sodium bitartrate-treated dams remained with their own mothers; 2) "crossfostered control group", in which pups from sodium bitartratetreated dams were fostered to nicotine-treated dams; 3) "nicotine group", in which pups from nicotine-treated dams remained with their own mothers; and 4) "cross-fostered nicotine group", in which pups from nicotine-treated dams were fostered to mothers who had received sodium bitartrate during their own pregnancy.…”

Prenatal stress induces spatial memory deficits and epigenetic changes in the hippocampus indicative of heterochromatin formation and reduced gene expression

“…These effects are especially apparent in various forms of learning and memory such as object recognition [3] and spatial memory [4]. The cognitive effects of prenatal stress (PNS) may be mediated through epigenetic changes such as histone acetylation and DNA methylation [5].…”