Effects of training in the Morris water maze on the spatial learning acquisition and VAChT expression in male rats

It has been well established that cholinergic pathway plays an important role in learning and memory processes. The present study was designed to evaluate the effects of Morris water maze [MWM] training on spatial memory acquisition and expression of the vesicular acetylcholine transporter [VAChT] in male rats. Methods: In this study, training trials of all groups of animals were conducted in the MWM task. Rats received one training session consisting of four trials per day which continued for another four consecutive days. Controls received visible platform MWM training. The escape latency, the traveled distance and swimming speed for each rat were recorded and used to evaluate the performance of the animal during training period. For evaluation of expression of VAChT protein levels, brain tissues from animals in each experiment were obtained immediately after the last trial on the related experimental day and processed for immunohistochemistry staining and western blotting analysis. There was a significant difference between animals subjected to one day training and those receiving four days of training in escape latency and travel distance. There were an apparent increase in VAChT immunoreactivity in the medial septal area [MSA] and CA1 region of the hippocampus in one day and four day trained animals compared with controls [visible group]. Quantitative immunostaining analysis by optical density measurements in the CA1 region and evaluation of immunopositive neurons in medial septal area of brain sections confirmed qualitative findings. Assessment of VAChT protein level expression in hippocampus by western blotting evaluation showed the same pattern of immunohistochemistry results. Overall, results of this study reveal changes in cholinergic neuron activity in different stages of training in the MWM task. Data suggest that there is a significant level of cholinergic neuronal activity during early stages of the training especially in the hippocampus region that may contribute to the apparent increase in VAChT expression

Time course effects of lithium administration on spatial memory acquisition and cholinergic marker expression in rats

The effects of chronic lithium exposure on spatial memory in rats remain controversial. In this study a time course of the effects of lithium, administered systemically, on spatial memory acquisition in Morris water maze was investigated. Lithium [600 mg/L] was administered to four groups of rats in their drinking water; the first group of animals received lithium for one week, the second group for two weeks, the third group for three weeks, and the fourth group for four weeks. As controls, four groups of animals received only normal drinking water for the same period of time. Toward the end of their lithium or water treatment, all animals were trained for four days; each day included one block and each block contained four trials. Test trials were conducted 48 hrs after completion of the lithium treatment. Escape latency, traveled distance and swimming speed were evaluated during testing trials. Brain tissues from animals were processed according to the standard protocols for immunohistochemical analysis. Lithium treatment decreased escape latency and traveled distance, but not swimming speed, compared with controls, suggesting significant spatial memory acquisition enhancement by lithium. Quantitative analysis showed that lithium, particularly after four weeks of exposure, significantly increased the number and density of immunostained ChAT-containing [choline acetyltransferase] neurons in the medial septal area in comparison with control groups. There was also a significant correlation between the number of immunostained ChAT neurons and behavioral measures. These results suggest that chronic oral administration of lithium causes spatial memory acquisition improvement in rats and an increase in ChAT immunostaining levels in medial septal nuclei