Increased plasma ACTH in rats exposed to the elevated plus-maze is independent of the pineal gland.

The involvement of the pineal gland in activation of the hypothalamic-pituitary-adrenocortical (HPA) axis evoked by a stressful stimulus (exposure to the elevated plus-maze) was investigated. Plasma ACTH levels were measured in pinealectomized and pineal-intact rats (sham-operated and non-operated) immediately after a 5 min placement into a plus-maze. A statistically significant elevation in plasma ACTH was measured within all groups; however, no statistical differences between pinealectomized and pineal-intact rats were observed. Similarly, comparison of the plasma ACTH basal values obtained from animals only kept in their home cages did not reveal any statistical differences between pinealectomized and pineal-intact rats. From these results it can be concluded that the pineal gland is not involved in anxiety-related behavior and ACTH response.