Abstract
The aim of this study was to determine the mRNA expression of nitric oxide synthetase (NOS, argininosuccinate synthetase (AS), argininosuccinate lyase (AL) and glutamine synthetase (GS) in different regions of brain in rats subjected to kainic acid (KA) mediated epilepsy. The short term (acute) group animals were sacrificed after 2 h and the long term (chronic) group animals were sacrificed after 5 days of single injection of KA. After decapitation of rats, cerebral cortex (CC), cerebellum (CB) and brain stem (BS) were separated and in their homogenates, the relative amount of nNOS, iNOS, AS, AL and GS mRNA was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). Results showed an increased expression of iNOS in all brain regions tested in chronic group as compared to either control or acute group, and it indicate a favorable condition of nitric oxide production. AL expression was significantly increased only in CB in acute group whereas in chronic group it is increased in CC and CB and decreased in BS as compared to control. The aforementioned increased expression of AL may contribute effective recycling of citrulline to arginine. No change in expression of nNOS and AS in both acute and chronic groups of epilepsy. GS expression was significantly decreased only in chronic group of epilepsy in all brain regions tested when compared with control group. The decreased GS may be contributing prolonged availability of glutamate in chronic epilepsy. Key words: Citrulline-nitric oxide cycle enzymes, glutamine synthetase, reverse transcriptase-polymerase chain reaction (RT-PCR), epilepsy.
Highlights
Generation of nitric oxide (NO), a versatile molecule in signaling processes and unspecific immune defense, is intertwined with synthesis, catabolism and transport of arginine which participates in the regulation of a fine-tuned balance between normal and pathophysiological consequences of NO production (Wiesinger, 2001)
The aim of this study was to determine the mRNA expression of nitric oxide synthetase (NOS), argininosuccinate synthetase (AS), argininosuccinate lyase (AL) and glutamine synthetase (GS) in different regions of brain in rats subjected to kainic acid (KA) mediated epilepsy
NO is synthesized from arginine by nitric oxide synthase (NOS; EC 1.14.13.39), and the citrulline generated as a by-product can be recycled to arginine by successive actions of argininosuccinate synthetase (AS; EC 6.3.4.5) and argininosuccinate lyase
Summary
Generation of nitric oxide (NO), a versatile molecule in signaling processes and unspecific immune defense, is intertwined with synthesis, catabolism and transport of arginine which participates in the regulation of a fine-tuned balance between normal and pathophysiological consequences of NO production (Wiesinger, 2001). Earlier studies reported that NOS knockout mice were more severely affected by epileptic activity than controls and the response to NO during epilepsy depends on its concentration (Itoh and Watanabe, 2009). It was indicated that NO may be regarded as an anticonvulsant, as NOS knockout mice were more severely affected by epileptic activity than controls and proconvulsant, because high NO is formed in normal rats subjected to convulsions by pentylenetetrazole (PTZ) (Itoh and Watanabe, 2009). We reported the increased activities of NOS, AS and AL and decreased activity of GS in acute and chronic groups of KA mediated epilepsy (Swamy et al, 2011). The present study was conducted to assess the expression of nNOS, iNOS, AS, AL and GS in cerebral cortex (CC), cerebellum (CB) and brain stem (BS) of rats in acute and chronic groups of KA mediated epilepsy and thought, to provide additional information in understanding the increased generation of NO and its effects on GS modulation in KA mediated epilepsy
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