The number of hypothalamic IL-2-containing cells changed in rats receiving Vilon and Epithalon during mild stress (handling). The number of IL-2-positive cells in hypothalamic structures decreased 24 h after intramuscular injection of Epithalon and 2 h after intranasal administration of the test peptides. Adaptation of animals to experimental conditions prevented the decrease in the number of IL-2-positive cells in the supraoptic nucleus after intranasal administration of Epithalon.