Prolonged Social Isolation and Social Instability in Adolescence in Rats: Immediate and Long-Term Physiological and Behavioral Effects

Abstract

After weaning on the 21st day of life, Wistar rat pups were kept in groups of 4–5 individuals for six weeks (control group), in individual cages (social isolation group), or were subjected to alternate days of isolation and housing in groups of 10 rats with constant rotation of partners (social instability group). Some of the animals were then decapitated for investigations, while the remainder were tested and left undisturbed for two months in groups of 4–5 individuals. The animals were retested as adults. Body, thymus, and adrenal weight were measured, along with blood corticosterone levels at rest and in acute stress; basal testosterone levels, basal and stress systolic arterial blood pressure, and the amplitude and prepulse inhibition of the acoustic startle reaction were assessed, and the behavioral manifestations of anxiety and depression were evaluated. The results showed that social environment factors in adolescence affected the animals’ physiological and behavioral characteristics, some effects being transient and settling on subsequent housing in stable groups, others persisting into adulthood, and a third group becoming significant only as rats became adults.