Physical activity influences spatial memory, seizure susceptibility, and seizure-related hippocampal damage

The hippocampus, a brain region important for learning and memory, is highly vulnerable to damage from a variety of insults. In addition to impairing important memory processes, hippocampal damage can lead to the development of seizures and eventually epilepsy. Therefore, protection of hippocampal neurons is considered a strategy in the prevention and treatment of epilepsy.; Exercise is a potent modifier of the brain and may play a useful role in hippocampus protection. In humans, exercise is a predictor of age-related cognitive decline and neurodegenerative disease. In animals, exercise reduces stroke-related hippocampal damage. To date, the influence of exercise on seizure-related memory impairment, and hippocampal damage has not been investigated.; The work presented here was formulated from the general hypothesis that exercise will reduce the likelihood of seizure development, and reduce the hippocampal damage and cognitive impairment associated with seizure. Rats had access to running wheels or remained sedentary for four weeks prior to an injection of the excitotoxic agent kainic acid, or an injection of saline. Kainic acid produced a prolonged seizure known as status epilepticus, which is a common cause of human epilepsy, and is associated with memory impairment and a reduction in the density of hippocampal neurons. Animals that exercised high levels during the training period were less likely to develop status epilepticus than those that exercised low levels or not at all. When hippocampal-related memory was assessed using the Barnes maze, high exercising animals performed better than low exercising and non-exercising animals and were less likely to suffer memory impairment after status epilepticus. Assessment of hippocampal neuronal density in two populations of cells revealed that exercising in general attenuated the decrease in CA3 neuron density following status epilepticus, and animals that were high exercising animals also had an attenuated decrease in CA1 neuronal density. Taken together, these data suggest that exercise is related to hippocampal function, and that animals that exercise high levels are less likely to develop seizure or to have brain damage and cognitive impairment following seizure.