The relevance of the endocrine condition in microglia morphology and dendrite complexity of doublecortin-associated neurons in young adult and middle-aged female rats exposed to acute stress.

Menopause, natural or surgical, might facilitate the onset of psychiatric pathologies. Some reports suggest that their severity could increase if the decline of ovarian hormones occurs abruptly and before natural endocrine senescence. Therefore, we compared the effects of ovariectomy on microglia's morphological alterations, the complexity of newborn neurons, and the animal's ability to cope with stress. Young adult (3 months) and middle-aged (15 months) female Wistar rats were subjected to an ovariectomy (OVX) or were sham-operated. After 3 weeks, animals were assigned to one of the following independent groups: (1) young adult OVX + no stress; (2) young adult sham + no stress; (3) young adult OVX + stress; (4) young adult sham + stress; (5) middle-aged OVX + no stress; (6) middle-aged sham + no stress; (7) middle-aged OVX + stress; (8) middle-aged sham + stress. Acute stress was induced by forced swimming test (FST) exposure. Immobility behavior was scored during FST and 30 min after; animals were euthanized, their brains collected and prepared for immunohistochemical detection of Iba-1 to analyze morphological alterations in microglia, and doublecortin (DCX) detection to evaluate the dendrite complexity of newborn neurons. OVX increased immobility behavior, induced microglia morphological alterations, and reduced dendrite complexity of newborn neurons in young adult rats. FST further increased this effect. In middle-aged rats, the main effects were related to the aging process without OVX or stress exposure. In conclusion, surgical menopause favors in young adult rats, but not in middle-aged, the vulnerability to develop immobility behavior, retracted morphology of microglial cells, and decreased dendrite complexity of newborn neurons.