Changes in the gene and protein expression of K(ATP) channel subunits in the hippocampus of rats subjected to picrotoxin-induced kindling.

ATP-sensitive K+ (KATP) channels couple the intracellular metabolic state to electrical activity, which is important in the control of neuronal excitability and seizure propagation. In this study, we investigated the changes in the gene and protein expression of KATP channel subunits in the brain of picrotoxin (PTX)-kindled rats, which were daily administered with a subconvulsant dose of PTX for 20 days. At 14 days after the last administration of PTX, kindled rats were retreated with PTX and killed by decapitation at 12 h, 1 and 3 days, as well as retreated with vehicle and killed at 0 h after starting the retreatment. The abundance of Kir6.1, Kir6.2, SUR1 and SUR2A/B mRNAs was evaluated by reverse transcription polymerase chain reaction (RT-PCR) using endogenous gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as an internal control, and the level of Kir6.2 and SUR1 proteins was measured by Western blot. At 0 h, the brain showed decreasing expression of various subunit mRNAs, with the exception of the SUR2A mRNA. In contrast, from 12 h to 3 days, the amount of various subunit mRNAs was up-regulated dynamically, but SUR2A of which was not changed significantly both from cortical and hippocampal samples. Furthermore, we demonstrated that the levels of Kir6.1, Kir6.2, SUR1 and SUR2B mRNAs at 12 h and 3 days (excepting SUR1 at 3 days) from hippocampal samples, as well as Kir6.1 at 1 day and SUR1 at 3 days from cortical samples, were significantly higher than that detected at 0 h. In addition, low levels of Kir6.2 and SUR1 proteins were observed both from cortical and hippocampal samples at 0 h and also, from 12 h to 3 days, a marked up-modulation of Kir6.2 and SUR1 protein expressions especially from hippocampal samples was found. These results suggest that the PTX-induced changes in the KATP channels may play a key role in the induction and maintenance of kindling and the PTX-induced seizures might be important for the acute changes of KATP channels observed in kindled rat brain.