الفهرس 
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Abstract
The aim of the present investigation was to study and compare the
possible prophylactic and therapeutic effect of astaxanthin on some aspects
of brain cognitive function & hippocampal DNA in rats exposed to chronic
unpredictable mild stress.
For this purpose; 84 adult male albino rats divided into four equal
groups, 21 rats each, were used: non-stressed (NS), stressed non-treated
(SNT), stressed astaxanthin pretreated (S+Ast pre) and stressed astaxanthin
post treated (S+Ast post).
At the end of experimental period (3 weeks); systolic blood pressure
was measured for each rat by using rat tail sphygmomanometer technique.
Then each group was randomly divided into three subgroups, 7 per cage,
for measuring different aspects of brain cognitive abilities:
1- Subgroup – a: for measuring spatial reference memory and learning
using Morris water maze test.
2- Subgroup – b: for measuring non spatial memory using Novel object
recognition test.
3- Subgroup – c: for measuring spatial working (short term) memory
using Y maze spontaneous alternation test.
At the next morning, fasting retro-orbital blood samples were
collected from all groups and were used for estimation of glycemic state
(fasting blood glucose, HbA1c, serum insulin and HOMA IR was
calculated), serum corticosterone level and lipid profile (total cholesterol,
triglycerides, HDLc and LDLc).
Then, rats were sacrificed by cervical elongation and dislocation and
skulls were opened and brains were extracted to isolate the hippocampus.
Tissues of left hippocampus was hemoginized and was used for measuring
total antioxidant capacity (TAC), malondialdehyde level (MDA), tumor
necrosis factor alpha (TNF-α), norepinephrine, dopamine, serotonin and
brain derived neurotropic factor (BDNF). Tissues of right hippocampus
was excised and preserved at -80 degree for DNA and RNA extraction and
studying the electophoretic pattern of both hippocampal nucleic acids.
In the present investigation, it was found that non spatial memory
(represented by discrimination index (d2) and recognition or preference
index, (d3) of novel object recognition test), spatial working (short term)
memory (represented by spontaneous alternation % of Y maze test), were
significantly lower in stressed non-treated (SNT) group when compared to
the corresponding values of non-stressed (NS) group, while escape latency
of MWM test ( representing decline in spatial reference memory), was
significantly higher. This was combined with significant DNA changes
(apoptosis pattern) and increased RNA in hippocampus of stressed nontreated (SNT) group when compared to the corresponding values of nonstressed (NS) group.