Aged rats learn Morris Water maze using non-spatial search strategies evidenced by a parameter-based algorithm

Protocol to investigate the gradual selection and deployment of goal-oriented search strategies during unsupervised navigation in mice

The ability of rodents to effectively navigate in an environment is based on trial-and-error learning and flexible decision-making and can be analyzed via navigational trajectories. We present a protocol for studying the deployment of search strategies in mice using the Morris water maze. We describe steps for assigning mice to different maze variations and procedures for post-training tracking and analysis. This protocol represents an effective behavioral readout to probe brain networks involved in strategy deployment and goal-oriented behavior. For complete details on the use and execution of this protocol, please refer to Parrini et al.1.

Morphofunctional Changes in Brain and Peripheral Blood in Adult and Aged Wistar Rats with AlCl3-Induced Neurodegeneration

BACKGROUND

the general lifespan has been prolonged greatly during the past century, and the incidence of age-associated diseases, including neurodegenerative ones, has increased as well. However, modelling of age-related pathologies is mostly conducted on adult rodents. We studied morphofunctional changes in the brain and peripheral blood of adult Wistar rats in comparison with old Wistar rats to determine age-related physiological changes and differences in adaptive reactions to AlCl3 exposure.

METHODS

the work was performed on adult and old male Wistar rats. The animals consumed a 100 mg/kg solution of AlCl3 each day for 60 days. Morphological changes of neurons and microglia, mRNA expression levels of pro-inflammatory and anti-inflammatory cytokines, microglia activation markers, amyloid-related proteins, and hallmarks of cellular senescence, monocyte, and lymphocyte subpopulations in the peripheral blood were examined.

RESULTS

old rats showed increasing hyperchromic neurons in the hippocampus; activation of microglia; upregulation of pro-inflammatory cytokines and cellular senescence markers; downregulation of anti-inflammatory cytokines; and Hif-1a and a decrease in B-cells and monocyte in peripheral blood.

CONCLUSION

compared to young animals, aged rats respond to aluminum exposure with a severe decline of most cells' function and irreversible neuronal loss. Regarding all reported data, neurodegeneration modelling and investigating of factors capable of accelerating or preventing it should be performed in experimental work on aged animals.

Age-related decline in cognitive flexibility is associated with the levels of hippocampal neurogenesis

Aging is associated with impairments in learning, memory, and cognitive flexibility, as well as a gradual decline in hippocampal neurogenesis. We investigated the performance of 6-and 14-month-old mice (considered mature adult and late middle age, respectively) in learning and memory tasks based on the Morris water maze (MWM) and determined their levels of preceding and current neurogenesis. While both age groups successfully performed in the spatial version of MWM (sMWM), the older mice were less efficient compared to the younger mice when presented with modified versions of the MWM that required a reassessment of the previously acquired experience. This was detected in the reversal version of MWM (rMWM) and was particularly evident in the context discrimination MWM (cdMWM), a novel task that required integrating various distal cues, local cues, and altered contexts and adjusting previously used search strategies. Older mice were impaired in several metrics that characterize rMWM and cdMWM, however, they showed improvement and narrowed the performance gap with the younger mice after additional training. Furthermore, we analyzed the adult-born mature and immature neurons in the hippocampal dentate gyrus and found a significant correlation between neurogenesis levels in individual mice and their performance in the tasks demanding cognitive flexibility. These results provide a detailed description of the age-related changes in learning and memory and underscore the importance of hippocampal neurogenesis in supporting cognitive flexibility.

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.