There are differences in stress reactivity between pre-puberty and adult rats. Previous studies showed that significant shifts in the reactivity of hypothalamic-pituitary-adrenal (HPA) axis during the pubertal stages of development. Although sympathetic nervous system (SNS) is activated by stressor including restraint stress (RS) in adult rats, it is not well understood whether RS induces the SNS activations in peri-pubertal stages. The aim of this study is to investigate the age-dependent changes in sympathetic reactivities, as stress response by a single and repeated RS, in peri-pubertal male rats.
Male Wistar rats at 25-28 postnatal days of age (PND) (pre-puberty) and PND 39-42 (mid-puberty), and PND 84-87 (adult) were used in this study. Rats were exposed to a single RS (1RS) or repeated RS for 4 consecutive days (4RS). Blood samples were collected immediately after termination of RS. Plasma catecholamines were measured by HPLC with electrochemical detection to evaluate the SNS activations.
As results, the levels of plasma catecholamines were significantly increased by 1RS in pre-pubertal rats compared to mid-pubertal and adult rats. In contrast, 4RS did not induce the increasing of the levels of plasma catecholamines in pre-pubertal rats. These results indicate that the SNS in pre-puberty is more severely activated by a single RS than that in mid-puberty and adult.