Effects of repeated unpredictable mild stresses to prewining rats and to nursing dams on the behavioral response of offspring to chronic stress in adulhood.

TORRECILLA MARIANA; GONZALEZ JATUFF A; QUERCETTI M.; RODRIGUEZ ECHANDÍA E.L.

American Journal of Neuroprotection and Neuroregeneration

American Scientific Publishers

Lugar: Valencia, California 91381-0751, USA ; Año: 2013

1947-2951

It has been shown that early life sensory experience can affect neural development and adult behavior. It was early reported that the first two postnatal weeks are a critical period for maturation of the neurotransmitter systems in rats (11). Among the external environmental influences that can modify neural development are the various types of mild stressful stimuli experienced by the developing organism. It has been reported that early handling (4), neonatal novelty (1), neonatal cold stress and random stressors (5, 6, 7) can develop greater emotional stability in adult life. Tolerance can develope when adult standard rats are repeatedly exposed to some predictable stressors (8). This  does not occur, however, when adult rats are exposed to repeatedly unpredictable stresses  causing a behavioral depression-like syndrome and endocrine alterations (8, 9, 14, 19). The neonatal exposure of rats to various chronic stress models is known to provide protection to these  behavioral and endocrine effects of an unpredictable chronic stress in adulthood (4, 5, 6, 12, 19). It has been suggested that some influences of chronic neonatal manipulations might be mediated by changes in maternal behavior due to a daily mother- infant separation period  and to the influence of pup-produced stimuli (15). This could stimulate maternal licking/grooming behavior in rats and mice and can alter the hippocampal glucocorticoid receptor expression in the offspring by an epigenetic mechanism (20). It has been also reported, however, that maternal separation has little effect on the rat offspring and that other factors besides active maternal care may contribute to the persistent  offspring´s behavioral phenotype (7). The effect of exposure of nursing dams to the repeated unpredictable stress, that causes consumatory and motivational deficit consistent with a behavioral depressive-like syndrome in standard female rats, on emotionality and stress responses of their offspring as adult has not been reported. The purpose of the present experiments was to compare the effect of this model of chronic stress applied to dams during nursing with the effect of an equivalent stress exposure of preweaning pups on resistance of offspring to the repeated unpredictable chronic stress in adulthood.