[Effect of stress in early ontogeny on the circadian rhythm of rat corticosteroid function].

The effect of short-term stress (cooling) during different periods of early ontogenesis on the characteristics of circadian rhythm of the corticosteroid function in adult animals were studied in the experiments with rats. The stressing of 2--4 and 17--19 days old rats was shown to modify the phase characteristics of circadian rhythm of the basal function of suprarenals in the adults. The circadian characteristics of reaction of the adults to stress suffered respective changes. The stimulation in the early ontogenesis did not affect the function of isolated suprarenals, thus suggesting that the changes in phase characteristics of circadian periodicity of the corticosteroid function are based on the influence of early stress effects on the regulatory system of this function. The pattern of early stress effects modifying the rhythm depends on the age of animals under stress.