The Neuroprotective Effects Of Progesterone In Ovariectomized Rats

Objective:Hormone loss in women after menopause would lead to cognitive degradation. Recent studies have suggested that hormone replacement therapy (HRT) can reduce the risk of dementia, and improve brain function degradation. Moreover, it also makes contributions to delaying, even preventing the occurrence of AD. Hence, estrogen and progesterone have been widely used in various experimental models. The aim of this study was to explore the effects of progesterone in ovariectomized rats on learning and memory in rats and its mechanism.Methods:A total of60female Sprague-Dawley (SD) rats, three months old, were randomly divided into six groups:normal control (normal), ovariectomized (OVX), ovariectomized+progesterone (OVX+P), ovariectomized+sesame oil (OVX+oil), sham+progesterone (sham+P), sham+sesame oil (sham+oil)(n=10for each group). The rats in OVX+P and sham+P groups were received subcutaneous injection of progesterone,20mg/kg, And the rats in OVX+oil and sham+oil groups received injection of same volume of sesame oil, every7days for4administration. The learning and memory ability were tested on a Morris water maze3weeks later, the expression level of Caspase-3, Bcl-2,5-HT-2A, GFAP and NF-kBp65protein in hippocampal neurons were detected by immunohistochemistry and Western Blot, At the same time, cell ultrastructure and cell apoptosis in rats brain hippocampus nerve were observed respectively using a transmission electron microscope and TUNEL.Results:1. The escape latency of OVX was significantly longer than the control group (p<0.01). The number for rats crossing platform effectively decreased compared with the control (p<0.01). Injection of progesterone led to apparent improvements in learning (p<0.01) and memory (p<0.05) compared to OVX group.2. Immunohistochemistry showed the numbers of GFAP positive cells in normal、 OVX+P、sham+P、sham+oil were less (p<0.01) than those of OVX and OVX+oil, respectively. The numbers of caspase-3positive cells in normal、OVX+P、sham+P、 sham+oil were less (p<0.01) than those of OVX and OVX+oil. The number of5-HT-2A positive cells in normal、OVX+P、sham+P、sham+oil were more (p<0.01) than those of OVX and OVX+oil. The number of NF-kBp65positive cells in normal、 OVX+P、sham+P、sham+oil were less (p<0.01) than those of OVX and OVX+oil. While the numbers of Bcl-2positive cells in normal、OVX+P、sham+P、sham+oil were more (p<0.05) than those of OVX and OVX+oil.3. Western blot analysis showed that the gray value both of GFAP in normal (p=0.013) and OVX+P (p=0.012) were lower than the OVX group. The gray value of Bcl-2in normal was higher than the OVX (p=0.000), OVX+P was higher than the OVX and OVX+oil group (p=0.000). The gray value of caspase-3in normal was lower than the OVX (p=0.000), OVX+P was lower than the OVX and OVX+oil group (p=0.001and0.016). The gray value of5-HT-2A in normal was higher than the OVX (p=0.000), OVX+P was higher than the OVX and OVX+oil group (p=0.000and0.000). The gray value of NF-kBp65in normal (p=0.009) and OVX+P (p=0.002) were lower than the OVX.4. Tunel staining showed apoptosis cells in OVX+P, sham operation groups were less than OVX (p<0.01).5. TEM showed that:In the groups of OVX and OVX+oil, the results seem the worst, synaptic partially denatured, the number of synaptic gap decreased, density of postsynaptic material were weaker, the inner mitochondrial were cloudy and swelling.In the groups of the normal. sham+P and sham+oil, the results seem the best, synaptic number were more, structure were clear, postsynaptic membrane had a compact electronic material, also many visible mitochondria. Moreover, organelles had complete structure.In the groups of OVX+P, the results showed postsynaptic dense electronic material reinforced, organelle integrity.Conclusion:progesterone can shorten escape latency, and enhance space exploration. It can also decrease the expression level of GFAP, caspase-3and NFkBp65, whereas elevate the level of Bcl-2,5-HT-2A in the hippocampus, Our results demonstrate that exogenous progesterone may slow the nerve cell apoptosis, maintain neuronal survival, and improve learning and memory in rats. All above show progesterone is effective to improve brain function degradation and delay, even prevent the occurrence of AD.