Senescence related alteration in hippocampal biogenic amines produces neuropsychological deficits in rats

Aging is a natural complex process that is regulated at genetic, cellular, molecular and systemic levels and leads to the development of a variety of changes including structural, chemical and genetic in the senescent brain. The major goal of the present study was to investigate the age associated cognitive dysfunction and other behavioral changes and their association with age related alterations in levels of neurotransmitters, such as dopamine (DA) and serotonin (5- HT) in the hippocampal region. Twelve male Albino Wistar rats were taken for the study including six young rats (04-05 months old) and six aged (20-22 months old) rats in each group. The learning and memory performance of rats was assessed by passive avoidance test (PA) and novel objective recognition task (NOR). Ambulatory activity was monitored by Open field test. Light/Dark transition test was used to monitor anxiety, whereas depression like symptoms was examined by Forced Swim Test (FST). Results showed that aged rats exhibited learning and memory impairment in PA and NOR. There was a negative relation between aging process and locomotion, consistent with previous findings. Moreover, an augmented increase in level of anxiety and depression was also observed in senescent rats. A marked decrease in DA and 5-HT was observed in the hippocampus of aged rats. Similarly, levels of 5-HIAA and DOPAC were also found to be decreased in aged rats. It is therefore concluded that age has a negative influence on cognitive function, depression, anxiety and locomotion in rats. Cells in all brain regions, especially hippocampus are affected by aging. In general aging exhibits a decline in sensory, motor and cognitive functions. These behavioral changes or functional deficits may be attributed to the age related decline in the levels of different neurotransmitters in brain /hippocampus. The present findings of behavioral deficits and altered neurotransmission in hippocampus of aged rats suggest a relationship between senescence, altered brain neurotransmitters and behavioral deficits.