ABSTRACT

Mercury is a widespread environmental and industrial pollutant which is used in food

preservation, cosmetics, pharmaceutical companies and laboratories. The aim of the

present study was to investigate the possible effects of mercury (Hg) exposure on the

histomorphology of the hippocampus, cerebellar and cerebral cortices, and also to

evaluate the effects of mercury on spatial learning and memory, and motor activity

with the aid of Morris water maze and Montoya staircase tests respectively. Twenty

four adult Wistar rats of both sexes, with average weight of 210gms were randomly

divided into four groups I, II, III, and IV with six animals per group. The animals in

groups II, III, and IV were administered mercury chloride orally at the concentration

of 12.45, 24.9 and 49.8 mg/kg body weight respectively while group I served as

control and was administered with normal saline. The administration lasted for a

period of 21 days (3 weeks). Animals were trained for both spartial learning and

memory, and motor function using Morris water maze and Montoya stair case tests

respectively. The brain tissues was fixed in Bouin’s fluid and processed for

histopathological studies using H and E and Bielschowsky stains. Brain tissues were

analyzed for trace element analysis using Neutron Activation Analysis (NAA-1). The

results from spartial learning and memory test was statistically significant after the

first week of administration of mercury chloride in group IV animals, by the second

week, there was an increase in time to find the platform, also by third week of

exposure to low dose of mercury, there was a statistical significant increased in latency

time taken to find the platform as an escape route by the rats. The result from Montoya

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staircase test showed reduced exploratory motor activity in rats exposed to high

concentration of HgCl2 that was statistically significant in the third week. There was

significant motor exploratory activity impairment due to mercury intoxication even at

low doses. The trace element analysis with NAA-1 revealed a significant decrease in