The effects of mineralocorticoid receptor antagonist on hippocampal functions in ovariectomized female rats with chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion (CCH) is a primary cause of vascular dementia, the incidence of which is increasing in the aging population, particularly affecting postmenopausal women. It is considered a major predisposing factor for cognitive impairment. The aim of the present study was to investigate the effects of the mineralocorticoid receptor antagonist spironolactone, administered at different doses, on hippocampal dysfunction induced by CCH, and to elucidate possible underlying mechanisms. A total of 48 female Wistar Albino rats (2 months old, weighing 130–190 g) were used. Based on body weight, the rats were randomly divided into four groups with 12 rats in each: (1) CONTROL, (2) CCH, (3) CCH+SPI25, and (4) CCH+SPI50. All animals underwent bilateral ovariectomy to induce menopause, and were kept for 5 weeks post-surgery to allow menopausal state to stabilize. CCH was induced using a modified two-step procedure by ligating the right common carotid artery followed one week later by the left. Spironolactone was administered orally by gavage at doses of 25 mg/kg and 50 mg/kg daily for 21 days in groups 3 and 4, respectively. To assess the effects of CCH and spironolactone on learning and memory, the Morris water maze test was employed. At the end of the experiment, blood pressure and heart rate measurements were taken, and the animals were sacrificed. Neuronal density in the CA1 and CA3 regions of the hippocampus was evaluated by a pathologist using hematoxylin and eosin (H&E) staining. Additionally, biochemical analyses were conducted to determine levels of malondialdehyde (MDA), protein carbonyls, catalase, and glutathione (GSH) in brain tissue, as well as hippocampal levels of NRF2, IL-1β, TNF-α, NLRP3, JAK2, STAT3, BDNF, CREB, CaMKII, GLT-1, and AChE. Results from the Morris water maze test revealed prolonged latency to find the platform and reduced time spent in the target quadrant in CCH animals, indicating impaired learning and memory. Spironolactone treatment ameliorated these cognitive deficits. It significantly reduced MDA and protein carbonyl levels, while increasing catalase and GSH levels. Furthermore, spironolactone elevated hippocampal levels of NRF2, CREB, and CaMKII, while decreasing GLT-1 and AChE levels. No significant changes were observed in IL-1β, TNF-α, NLRP3, JAK2, STAT3, or BDNF levels with either dose. Findings from this study suggest that especially the 50 mg/kg dose of spironolactone may alleviate oxidative damage, synaptic dysfunction, and impairments in neurotransmission systems independently of its blood pressure-lowering effects. It also appears to preserve the number of viable neurons in both CA1 and CA3 regions, thereby enhancing hippocampal function and mitigating cognitive decline. This is the first study in the literature to examine the potential effects and mechanisms of spironolactone on hippocampal dysfunction and cognitive deterioration in a CCH model.