[LONG-TERM EFFECTS OF STRESSFUL IMPACTS DURING NEONATAL PERIOD OF DEVELOPMENT ON NOCICEPTIVE SYSTEM AND PSYCHOEMOTIONAL BEHAVIOR].

Long-term effects of peripheral pain, brief stress of maternal isolation and their combination in one-day- and repeatedly two-day-old rat pups or seven-day- and repeatedly eight-day-old pups were investigated on indices of basal pain (in the absence of inflammation), a prolonged response to again evoked inflammation in the formalin test, the level of anxiety and depression and of spatial learning ability in the animals as adults (90-day-olds). Changes in the indices under investigation were revealed in adult rats depending on the type of early life impact and age during which it occurred: inflammatory pain induced hypoalgesia in the test of hot plate and deterioration in spatial learning ability in the Morris test; the stress of maternal isolation on the first and second days, but not seventh and eighth days of life caused a strengthening of formalin-induced pain response. Regardless of the age when rat pups were exposed to impact, again induced inflammation evoked strengthening of pain response when the animals reached adulthood. In the forced swim test the time of immobility was increased in rats exposed early to any from impacts investigated. The effect of combination pain with stress did not exceed the effect of each impact separately. The new data contribute to the urgent problem of the long-term effects of the damaging impacts of pain and stress during the neonatal period on the functional activity of the tonic nociceptive system and behavior.

[INVOLVEMENT OF 5-HT1A RECEPTORS IN LONG-TERM INFLUENCE OF INFLAMMATORY PAIN AND STRESS IN EARLY AGE ON REACTIVITY OF NOCICEPTIVE SYSTEM].

Effects of inflammatory pain, short stress of maternal isolation and combination of these impacts in 1-day-old and repeatedly 2-day-old rat pups (neonatal period of development) on the indices of generalized pain and the inflammatory pain response were studied on the rats during the adulthood. To study the involvement of 5-HT1A receptors in the long-term impact of neonatal effects on pain sensitivity we used a chronic injection of 5-HT1A receptor agonist buspirone during the prepuberal period of rats which as newborn experienced similar impacts (control, injection of saline). It was found that in adult rats in which inflammatory pain and stress of maternal isolation during the first two days of life caused changes in pain sensitivity, buspirone normalized the indices of basic pain in the hot plate test and the pain response in the formalin test; the combination of these impacts did not cause any changes in the pain sensitivity, and the effect of buspirone did not appear. Thus, effects of buspirone found in this study suggest that 5-HT1A receptors are involved in the long-term influence of the studied adverse neonatal impacts on the reactivity of the nociceptive system.