[EFFECT OF PRENATAL STRESS ON SEROTONERGIC NEURONS IN DORSAL RAPHE NUCLEUS AND ON PAIN BEHAVIOR DURING NEONATAL...

The effects of prenatal stress on immunocytochemical reaction on serotonin (5-HT) in the dorsal raphe nucleus (DRN) of the brainstem were investigated in 7-day-old male rat pups exposed to impact of pain in the formalin test (a control is an injection of saline). A strengthening effect of prenatal stress on pain behavior was revealed in animals in the formalin test. Prenatal stress decreased the number of 5-HT-immunoreactive neurons as compared with that in prenatally non-stressed animals in both pups with inflammatory pain and the controls. There were no differences in the number of 5-HT-immunoreactive cells between pups with inflammatory pain and saline in both prenatally non-stressed animals and prenatally stressed ones. The data suggest that stress of maternal separation during the experiment hides the difference in immunocytochemical result in the rat pups with inflammatory pain and in the control. Thus, it was demonstrated for the first time that in 7-day-old rat pups the 5-HT-ergic neurons in DRN of the brainstem are a target of the prenatal stress.