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© 2015, Springer-Verlag Berlin Heidelberg. Synaptic reorganization in the epileptic hippocampus involves altered excitatory and inhibitory transmission besides the rearrangement of dendritic spines, resulting in altered excitability, ion homeostasis, and cell swelling. The potassium-chloride cotransporter-2 (KCC2) is the main chloride extruder in neurons and hence will play a prominent role in determining the polarity of GABAAreceptor-mediated chloride currents. In addition, KCC2 also interacts with the actin cytoskeleton which is critical for dendritic spine morphogenesis, and for the maintenance of glutamatergic synapses and cell volume. Using immunocytochemistry, we examined the cellular and subcellular levels of KCC2 in surgically removed hippocampi of temporal lobe epilepsy (TLE) patients and compared them to control human tissue. We also studied the distribution of KCC2 in a pilocarpine mouse model of epilepsy. An overall increase in KCC2-expression was found in epilepsy and confirmed by Western blots. The cellular and subcellular distributions in control mouse and human samples were largely similar; moreover, changes affecting KCC2-expression were also alike in chronic epileptic human and mouse hippocampi. At the subcellular level, we determined the neuronal elements exhibiting enhanced KCC2 expression. In epileptic tissue, staining became more intense in the immunopositive elements detected in control tissue, and profiles with subthreshold expression of KCC2 in control samples became labelled. Positive interneuron somata and dendrites were more numerous in epileptic hippocampi, despite severe interneuron loss. Whether the elevation of KCC2-expression is ultimately a pro- or anticonvulsive change, or both—behaving differently during ictal and interictal states in a context-dependent manner—remains to be established.

Background: Nitric oxide (NO), synthesized by neuronal (nNOS), endothelial (eNOS), and inducible (iNOS) nitric oxide synthases, plays an essential role in the physiological functions of the gastrointestinal (GI) tract. Chronic ethanol intake has been shown to interfere with several of these physiological functions, leading to the pathological alterations observed in alcoholic individuals. Our aim therefore was to investigate the effects of chronic ethanol consumption on NOS isoforms in different GI segments. Methods: Rats received either 20% aqueous ethanol solution or water for 8 weeks. Tissue samples of the duodenum, jejunum, ileum, and colon of the rats were used for measurement of the NOS activity, protein content, and nNOS immunohistochemistry. Anti-HuC/D immunohistochemistry was used to determine the total number of neurons. Results: Measurement of the physiological constitutive NOS (cNOS) activity revealed a 20 times higher activity in the colon than in the small intestine and after chronic ethanol treatment demonstrated a significant decrease in the jejunum, ileum, and colon, while in the duodenum it remained unchanged compared with the control group. The physiological iNOS activity was higher in the ileum and colon than in the duodenum and jejunum, and these levels were not significantly affected by ethanol. Neuronal nitric oxide synthase immunohistochemistry revealed a significant decrease in the numbers of immunostained cells in all investigated intestinal segments, while the total number of myenteric neurons remained constant. The nNOS protein content measured by Western blotting indicated a significant decrease in the colon after ethanol consumption, while in other intestinal segments change was not detectable. Conclusions: This study has demonstrated for the first time that chronic ethanol consumption has a differential effect on NOS activity, NOS protein content, and the number of nitrergic neurons in different intestinal segments, suggesting that chronic ethanol administration affects the NO pathways in the enteric nervous system.