Hippocampal synaptic dysfunction and spatial memory impairment in omeprazole-treated rats

Although the association of prolonged use of proton pump inhibitors, such as omeprazole, with memory impairment has been reported more than two decades ago, its underlying molecular mechanism is yet to be determined. Thus, in this study, we aimed to determine the mechanisms underlying the effect of prolonged omeprazole treatment on hippocampal synaptic function and spatial memory in male rats. Adult rats were subcutaneously administered with omeprazole for 12 or 24 weeks. Spatial memory was assessed using the Morris water maze (MWM) test. We examined the hippocampal protein expression of synaptic plasticity proteins, including the AMPA receptor subunit GluA1, postsynaptic density-95 (PSD-95), and activity-regulated cytoskeleton-associated protein (Arc), and the hippocampal expression and localization of androgen receptor (AR). In the MWM test, the escape latency was found to be significantly higher, and the number of platform crossings and the time spent in the target quadrant were significantly lower in the rats treated with omeprazole compared to the control rats. Hypomagnesemia and lower bone and brain Mg²⁺ content were also detected in the omeprazole-treated groups compared with the control group. The expression of GluA1, PSD-95, and Arc in the hippocampus and the expression of AR in the dentate gyrus and CA1 of the hippocampus were significantly lower in the omeprazole-treated groups than in the control group. These results suggest that prolonged omeprazole treatment might lead to memory deficit by impairing glutamate receptor trafficking or synaptic anchoring. Hypomagnesemia and brain Mg²⁺ deficiency may be, at least in part, involved in omeprazole-induced memory impairment.