| Objectives: Except the common symptoms of epilepsy, about 30%-40% of the epileptic patients have been found to have deleterious cognitive consequences, which may affect the patients'life greatly, such as the declination of memory, the scattering of attention, etc. Despite the fact that the relationship between epilepsy and the cognitive deficiency has drawn much attention and become one of the focuses of modem epilepsy research. As well as the pathogen of epilepsy and the side effects of antiepileptic drugs, the epilepsy itself is one of the main factors for cognitive impairment in patients with epilepsy. We used pentylenetetrazole to establish a stable animal model of chronic epilepsy, and applied NMDA receptor antagonist-memantine to intervene the chronic epileptic rats. We also observed the learning and memory changes of epileptic rats by Morris water maze, as well as applied immunohistochemistry and RT-PCR to detect GAP-43 protein and transcription levels, to study the role of memantine on epileptic rats, and to explore the molecular mechanism of the cognitive impairment of epilepsy.Methods: Adult male Sprague-Dawley (SD) rats were selected through Y-Maze tests and then divided into 5 groups randomly. The 20 rats in the normal control group (NC) were injected saline intraperitoneally (i.p) by 3.5ml/kg for consecutive 44 days. The 30 rats in PTZ group received intraperitoneal injection of 1% pentylenetetrazol (PTZ) by 35mg/kg for consecutive 44 days. The 20 rats in PTZ+MMT(5) group received intraperitoneal injection of 1% PTZ by 35mg/kg for consecutive 30 days. From the 31st day on,the rats in PTZ+MMT(5) group were injected memantine intraperitoneally by 5 mg/kg 30 minutes before PTZ in the rest 14 days. The 20 rats in PTZ+MMT(10) group received intraperitoneal injection of 1% PTZ by 35mg/kg for consecutive 30 days. From the 31st day on,the rats in the group were injected memantine intraperitoneally by 10 mg/kg 30 minutes before PTZ in the rest 14 days. The 20 rats in PTZ+MMT(15) group received intraperitoneal injection of 1% PTZ by 35mg/kg for consecutive 30 days. From the 31st day on,the rats in the group were injected memantine intraperitoneally by 15 mg/kg 30 minutes before PTZ in the rest 14 days. Then those rats were tested with Morris Water Maze (MWM) for the measurement of learning and memory abilities. The expression of receptor GAP-43 transcription and protein levels were measured by reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry.Results: Beginning from day 3 on, rats in PTZ and PTZ+MMT groups had seizures induced by repetitive PTZ, which were characterized by head shaking, squealing and crawling. Moreover, loss of righting reflex and generalized tonic–clonic convulsions were seen on day 16~day 24, which indicated reaching the kindling standard. Rats were regarded as fully kindled when they exhibited seizure stagesⅣ~Ⅳin 3 times continuously. On day 30, the numbers of the rats being fully kindled in PTZ group, PTZ+MMT(5) group, PTZ+MMT(10) group,PTZ+MMT(15) group were 24, 15, 16, 14 respectively. No seizures were found in the NC group On day 31~day 44, the performance of PTZ group rats was like the former, as well as the PTZ+MMT(5) group, PTZ+MMT(10) group, PTZ+MMT(15) group still had seizures stagesⅣ~Ⅴ, but the lasting time of seizures and the recovering time after seizures were shorter than before.Place navigation results in MWM test: Comparisons were made among the mean escape latencies on each day. On day 1, comparisons of the five groups were no difference in significance(P>0.05). On day 2, the mean escape latencies of rats in PTZ group (23.85±5.66)s was much longer (P<0.01) than that in NC group (7.61±6.13)s. compared to NC group, PTZ+MMT(5) group (20..90±5.84) s and PTZ+MMT(5)group (21.20±5.23)s were longer(P<0.05); Moreover compared to PTZ+MMT(10) group, PTZ group was mush longer (P<0.01), PTZ+MMT(5)group and PTZ+MMT(15) group were longer (P<0.05).On day 3, the mean escape latency of the rats in PTZ group (15.51±1.27)s was obvious different from that in NC group (8.14±1.38)s and PTZ+MMT(10)group(9.78±2.23)s (P<0.01), and was different from that in PTZ+MMT(5) group (12.35±1.87)s and PTZ+MMT(15) group (14.98±1.54)s (P<0.05).Spatial probe test: The number of crossing times through the platform quadrant within 60 s in PTZ group(2.37±0.60) decreased obviously compared with that in NC group(5.17±1.39)(P<0.01). The number of crossing times in PTZ+MMT(10) group(4.68±1.28) increased obviously compared with that in PTZ group(P<0.01). There were no significant difference of the swimming time spent in the platform quadrant of the rats in four groups (P>0.05).The expression of GAP-43 mRNA in the hippocampus: The expression level in PTZ group(0.591±0.075) reduced obviously compared with that in NC group(0.817±0.051)(P<0.05).The expression of GAP-43 immunoreaction at CAl and DG of hippocampus in NC group and PTZ group: the immunoreactant was shown and most of them were in the plasmalemma of the neuron. The immunological reaction of GAP-43 for PTZ group at CA1 and DG were weak than NC group.Conclusion:Learning and memory ability of the PTZ-kindled epilepsy rats were impaired and Memantine might improve spatial learning and memory of pentylenetetrazole-kindled rats, the PTZ+MMT(10) group is the best.Meanwhile, the expression level of GAP-43 in hippocampus was decreased. Therefore, the impairment of learning and memory ability of the epilepsy rats might be related to the changes of GAP-43 in hippocampal neurons. |
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