Effects of prenatal acute stress on the behavioural reactivity in handled and non-handled rat progeny

The effects of prenatal stress are dependent on the intensity and duration of the stress treatment: chronic, uncontrollable stress causes an impairment in the normal adaptive responses to physical and physiological stimuli whereas acute and mild stress facilitates the morphological development of fetal brain neurons. The presents study was designed to investigate whether a single stress exposure during pregnancy may exert a facilitatory effect on the behaviour of the juvenile progeny. The effects of a postnatal handling procedure have been also investigated. One-month prenatally stressed rats (PSR) whose dams had been restrained for 120 minutes at the 16th day of gestation, showed an increased locomotor activity when tested in open-field (OF), decreased aversion to the open arms of the Elevated Plus Maze (EPM), a reduction in the responses to the Acoustic Startle Reflex (ASR). When tested at two months of age, these rats showed an increased performance in an operant learning task (OLT), with respect to controls. Postnatal Handling, from postnatal day (PND)3 to PND24 (weaning time), improved the performance in all the experimental condition in control rats, while did not affect PSR behaviour in OF , EPM, OLT, but increased the emotional response in the ASR. These data indicate that a prenatal exposure to an acute stress reduces emotionality and increased learning performance, in the progeny, and postnatal early experiences can modify the behaviour effects of prenatal stress. The stress-related effects on emotional and cognitive behaviour may be due to subtle modification in the development of nervous system of the offspring, depending on the prenatal stress schedule employed