Changes in Rat Adrenal Cortex and Pineal Gland in Inverted Light–Dark Cycle: A Biochemical, Histological, and Immunohistochemical Study

Abstract

Abstract Poor sleep standards are common in everyday life; it is frequently linked to a rise in stress levels. The adrenal gland interacts physiologically with the pineal gland in the stress response. Pineal gland is a small endocrine organ that modulates sleep patterns. This work aimed to evaluate the inverted light–dark cycle rhythm on the histological changes within the adrenal cortex and pineal gland in adult male albino rats. Twenty adult male albino rats were equally divided into two groups: For the first control group, animals were kept on daylight–darkness for 12–12 h. The second group was kept under an inverted 12- to 12-h light–darkness cycle for 4 weeks. Adrenal sections were subjected to biochemical, histological, and immunohistochemical study. Inverted light–dark cycle group recorded a significant elevation of plasma corticosterone, tissue malondialdehyde, tumor necrosis factor-α, and interleukin-1β (IL-1β) associated with a significant reduction of catalase and superoxide dismutase. Adrenal cortex showed biochemical and histological changes. Pineal glands also showed loss of lobular architecture. A significant upregulation in activated inducible nitric oxide synthase (iNOS) and B-cell lymphoma-associated X (Bax) immunohistochemical expression was recorded in adrenal cortex associating with downregulation in B-cell lymphoma 2 (Bcl-2). It could be concluded that subchronic inverted light–dark cycle exerted direct effects on adrenal cortex and the pineal glands.