Altered expression of G protein-coupled inwardly rectifier potassium channels (GIRK) subunit 1 and 2 in hippocampus of chronic temporal epileptic rats induced by kainic acid

AIM: G protein-coupled inwardly rectifier potassium (GIRK) channel are distributed widely in mammalian brain. In CNS, GIRK 1/2 seems to be the predominant heterotetramers which play a pivot role in the regulation of the excitability of neurons and may contribute to the resting potential by leading to a hyperpolarization of membrane potential and reduction of the action potential frequency. In the context, the Weaver mouse is the first neurological abnormality directly linked to a genetic point mutation in the GIRK2 protein which includes spontaneous seizure. GIRK2 knock out mice showed normal development but more susceptible than normal mice to seizure induced by GABA antagonist. Here, we report that the mRNA and protein expression of GIRK subunit 2 is altered in kainic acid(KA)-induced epileptic rat hippocampus. METHODS: Rats were injected with kainate 14 mg/kg intraperitoneally to establish an acute and chronic temporal lobe epilepsy model. At chronic spontaneous seizure stage, by using of in situ hybridization, immunocytochemistry and Western blotting, the GIRK 1,2 mRNA and protein were analyzed quantitatively in the dentate gyreus, CA1, CA3 regions of hippocampus. RESULTS: GIRK1,2 mRNA and proteins were expressed abundantly in all regions of hippocampus. KA induced seizures and caused a significant increase in GIRK2 mRNA abundance and immunoreacitivity; only GIRK1 mRNA was increased significantly, but no difference was found by Western blotting protocol. CONCLUSION: GIRK1,2 mRNA and protein expression in the hippocampus of epileptic rat brain is up-regulated, which may be an adaptive response to over-excitability of neuron networks and prevent the over-excitability spread in hippocampus (DG-CA3-CA1).     

Floral induction (FI) in longan (Dimocarpus longan, Lour.) trees. III: Effect of shading the trees on potassium chlorate induced FI and resulting hormonal changes in leaves and shoots

Previous experiments demonstrated that treatment of longan trees with potassium chlorate (KClO₃) induces “off season floral induction” (FI) even in the absence of the naturally required cool temperature [Manochai, P., Sruamsiri, P., Wiriya-alongkorn, W., Naphrom, D., Hegele, M., Bangerth, F., 2005. Year around off season flower induction in longan (Dimocarpus longan, Lour.) trees by KClO₃ applications: potentials and problems. Sci. Hortic. 104, 379–390]. Potassium chlorate, however, cannot replace the presence of functional mature leaves and sufficient light intensity. Here we examined in more detail the effect of shade (about 10% of natural sunlight) on KClO₃ affected hormone concentrations/transport of leaves and shoot apical buds (SAB) and their interactions with FI.