[Effect of neonatal influences on pain and audiogenic sensitivity and the content of monoamines in the adult rat brain].

In adult Wistar, KM, and Wag/Rij rats, the threshold of pain sensitivity (tail-flick test) and degree of spasm attack in response to a strong sound were estimated after neonatal administration of Semaks (analog of ACTG4-10 fragment) or after placebo (administration of saline for the control of the effect of neonatal pain stimulation). These neonatal influences did no affect the rates of sensorimotor maturation at an early age (Fox tests), i.e., did not affect directly the physiological activity of rat pups at the age of up to 21 days. In all control rats injected with saline (pain stimulation), the latent periods of audiogenic attacks increased reliably, while their degree decreased. Administration of Semaks "raised" these parameters to the lvl of those in intact animals, i.e., increased the sensitivity to sound. Neonatal administration (per os) of caffeine to KM rats increased reliably the latent period of audiogenic attacks. The thresholds of pain sensitivity in the rats of all strains were significantly lower than in the intact control, just as the level of dopamine in the hippocampus of KM rats. These data are interpreted as an evidence of changes in the development of some brain systems in response to neonatal influences.