Chronic h1-antihistamine treatment increases seizure susceptibility after withdrawal by impairing glutamine synthetase.

AIM: To investigate the effect of chronic H1-antihistamine treatment on seizure susceptibility after drug withdrawal in nonepileptic rats and to further study its relation to glutamine synthetase (GS), which is the key enzyme for glutamate metabolism and gamma aminobutyric acid (GABA) synthesis. METHODS: After drug withdrawal from a 2-week treatment with diphenhydramine or pyrilamine, seizure susceptibility was determined by amygdaloid kindling or pentylenetetrazol model; meanwhile, the GS expression or activity was analyzed. The glutamine, glutamate, and GABA contents were measured by high-performance liquid chromatography. RESULTS: Seizure susceptibility significantly increased in amygdaloid kindling and pentylenetetrazol model 10 days after drug withdrawal from a 2-week treatment with H1-antihistamines. Meanwhile, GS activity and expression in the cortex or hippocampus decreased simultaneously with a marked decline of glutamine and GABA content. Comparable inhibition of GS activity by methionine sulfoximine was also sufficient to increase the susceptibility, while supplementation with glutamine reversed the high susceptibility 10 days after diphenhydramine withdrawal. Moreover, the seizure susceptibility increased 10 days after diphenhydramine withdrawal in wild-type mice but not in histidine decarboxylase knockout mice, which lack histamine. CONCLUSIONS: Chronic H1-antihistamine treatment produces long-lasting increase in seizure susceptibility in nonepileptic rodents after drug withdrawal and its mechanism involves impairment of GS through blocking the action of histamine.

[Directed differentiation of mouse embryonic stem cells into neuronal cells induced by icaritin in vitro].

OBJECTIVE: To evaluate the inductive effects of icaritin (ICT) on the directed differentiation of mouse embryonic stem (ES) cells into neuronal cells in vitro. METHODS: ES cells were cultured with embryoid body (EB) formation cultures, ICT in different concentrations was added in the cultural media and the cells were harvested in several differentiation phases. The expression spectrums of neuronal cell-specific genes and proteins were verified by semi-quantitative RT-PCR and immunocytochemistry analysis, respectively. RESULTS: Differentiation of neurocyte phenotype from ES cells was promoted by ICT in a concentration-and time-dependent manner. ICT at 10(-7)mol/L significantly enhanced the differentiation toward neuronal cells, and up to 80 % of EBs outgrowth in d 8+8 incubation. The gene expressions of beta-tubulin III in neuron and GFAP in glial cells were detected in neuronal cell phenotype derived from EBs. Furthermore, nestin was detected in precursor cells, beta-tubulin III and GFAP were detected in the generated precursor neurocytes immunocytochemically. CONCLUSION: Directed differentiation of neurons is facilitated by ICT in EB formation culture, which is associated with the expression of developmental-dependent gene and protein.

[Protective effect of icaritin on apoptosis of primarily cultured rat neurons induced by Abeta25-35 peptide].

OBJECTIVE: To investigate the protective effects of icaritin (ICT) on apoptosis of primarily cultured rat neurons induced by Abeta(25-35) peptide and its mechanism. METHODS: Cortical neurons from rat embryonic cortical on d17 pregnancy were cultured in neural basal medium for 7 days. Icaritin (ICT) was pre-incubated for 24 h before adding Abeta(25-35) peptide and then the cells were incubated for 72 h. Neuroprotective effects of ICT were evaluated by MTT assay, LDH level in medium and cell morphological observation. Meanwhile, apoptosis was determined by JC-1 staining for mitochondria membrane potential (DeltaPsim) and AO/EB double staining for genetic damage of nucleoli in monolayer cells. RESULTS: 0.1 micromol.L(-1) ICT pre-incubation for 24 h prevented rat neurons from Abeta(25-35) peptide induced apoptosis significantly as demonstrated by MTT, LDH assay and morphological observation. AO/EB double staining also indicated that ICT prevented neurons from apoptosis. JC-1 staining further showed that ICT prevented decreasing of mitochondrial DeltaPsim induced by Abeta(25-35) peptide. CONCLUSION: ICT could protect primarily cultured rat neurons from Abeta(25-35) peptide induced apoptosis.