Level of Heat Shock Protein 70 in the Brain after Seizure Induction in Normo- and Hyperglycemic rats: Relationship to Neurotransmitters Level

Abstract

Although heat shock protein 70 (Hsp70) has been suggested to be a stress marker or to play a protective role in brain injury, the relevance of its expression in epilepsy and hyperglycemia is unclear. The aim of this study was to evaluate the level of Hsp70 in the rat hippocampus following pilocarpine induced seizure in normo- and hyperglycemic rat and its relation to glutamate and γamino-butyric acid (GABA) level. This study was carried out on 40 adult male albino rats divided into two main groups 20 rats per each; Group I: induction of seizures in normal rats; Ia: 10 control rats were injected with intraperitoneal (i.p.) saline. Ib: 10 rats were injected with pilocarpine (310-320mg/kg,ip) for seizure induction. Group II: induction of seizures in diabetic rats; 20 rats were rendered diabetic for one month by the injection of streptozotocin. Then they were subdivided into 2 subgroups; Group II a: 10 diabetic rats were injected with i.p. saline. Group II b: 10 diabetic rats were injected with i.p. pilocarpine. Development ofdiabetes was confirmed bymeasuring blood glucose levels in blood samples taken from tail vein.At the end of experimental period rats were sacrificed and the hippocampi were bilaterally dissected and handled to estimate levels of Hsp70, glutamate and GABA concentration. The results revealed significant increase in Hsp70 concentration in hippocampus after experimental seizures, Hyperglycemia alone was not associated with significant change in Hsp70 level in group IIa compared to control. Nosignificant difference in Hsp 70 level was found between hyperglycemic rats with and without seizure induction. Levels of glutamate and GABA were not changed significantly after pilocarpine administration. Hyperglycemia followed by seizure induction was associated with significant increase in glutamate and decrease in GABA level. On the other hand, hyperglycemia alone failed to exert any significant change in NTlevels. The current study therefore, suggested that Hsp70 could play a role in neuroprotection during an epileptogenic state as evidenced by low scores of seizure in rats and levels of NT; in addition, Hyperglycemia is associated with impairment of Hsp70 expression; therefore, the neurons were more vulnerable to the damaging effect of pilocarpine as showed in severe seizure attacks and significant changes in NT level.