Glial Cells and their Ultrastructural Relationship with Neurosecretory Endings in The Neural Lobe of the Egyptian Lesser Jerboa (Jaculus Jaculus) Under Different Hydration States

Introduction: The neural lobe (NL), stores and releases vasopressin which is vital for water conservation, following dehydration. Through dividing and changing phenptypes, glial cells of NL, closely associated to neurosecretory axons and capillaries, show unique structural remodeling and functional adaptations, to participate in neurosecretion. In Jaculus jaculus, a desert rodent surviving without direct water intake, we hypothesize that NL glial plasticity is an important adapting mechanism in enhancing vasopressin efficiency release, to counter dehydration. Aim of the Work: To characterize glial cell phenotypes in the hypophysis NL and analyze their structural relationships with neurosecretory terminals of the hypothalamic supraoptic and paraventricular magnocellular neurosecretory neurons of the Egyptian lesser jerboa, blood capillaries, and the boundary between the hypophysis neural and intermediate lobes under different hydration states. Materials and methods: Adult male jerboas were divided into two groups: one received dry barley seeds (dehydrated group, n = 6), and the other received fresh vegetables (hydrated group, n = 6) for 12 days. hypophysis NL tissues microanatomy was analyzed by immunohistochemistry using anti-S100 and anti-GFAP antibodies, glial markers, and transmission electron microscopy. Results: In the dehydrated group, blood capillaries within the hypophysis NL were enlarged. S100 immunoreactivity was present in both groups, while GFAP was absent in the hydrated group. Ultrastructurally, the dehydrated group exhibited lipid-rich pituicytes forming dense networks, and other glial cells engulfed neurosecretory terminals and swellings. In contrast, the hydrated group had predominantly phagocytic glial cells containing substantial intracellular debris within a loosely organized parenchyma with sparse terminal endings. Conclusion: Three phenotypic subtypes of glial cells in the hypophysis NL of Jaculus jaculus are identified: (i) lipid-rich interconnected pituicytes, (ii) pituicytes surrounding terminal endings and wellings (iii) phagocytic pituicytes. These results suggest that hydration acts as a physiological stressor in this desert-adapted species, potentially inducing remodeling changes in the NL.