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Aim As severe alcohol intoxication impairs memory function, a high concentration of ethanol (60 mmol L−1) acutely inhibits long-term potentiation (LTP), a cellular model of learning and memory, in rat hippocampal slices. Neurosteroids are involved in this LTP inhibition. We recently reported that the inhibitory effects of 60 mmol L−1 ethanol are blocked by 4-methylpyrazole (4MP), an inhibitor of alcohol dehydrogenase, suggesting that acetaldehyde locally generated within the hippocampus participates in LTP inhibition. We investigated whether acetaldehyde generated by ethanol metabolism contributes to neurosteroidogenesis and LTP inhibition. Results Like 60 mmol L−1 ethanol, we found that exogenous acetaldehyde enhanced neurosteroid immunostaining in CA1 pyramidal neurons, and that augmented neurosteroid immunostaining by high ethanol alone was blocked by 4MP, but not by inhibitors of other ethanol metabolism pathways. The inhibitory effects of 60 mmol L−1 ethanol on LTP were mimicked by a lower concentration of ethanol (20 mmol L−1) plus acetaldehyde (60 μmol L−1), although neither agent alone was effective at these concentrations, suggesting that 60 mmol L−1 ethanol inhibits LTP through multiple actions, one of which involves acetaldehyde and the other of which requires just 20 mmol L−1 ethanol. The effects of ethanol and acetaldehyde on neurosteroid staining and LTP were overcome by inhibition of neurosteroid synthesis and by blockade of N-methyl-D-aspartate receptors (NMDAR). Conclusion These observations show that acetaldehyde generated by local ethanol metabolism within the hippocampus serves as a signal for neurosteroid synthesis in pyramidal neurons, and participates in the synaptic dysfunction associated with severe alcohol intoxication.

Children with neurofibromatosis type 1 (NF1) are prone to learning and behavioral abnormalities, including problems with spatial learning and attention. The molecular etiology for these deficits is unclear, as previous studies have implicated defective dopamine, cyclic adenosine monophosphate (cAMP), and Ras homeostasis. Using behavioral, electrophysiological, and primary culture, we now demonstrate that reduced dopamine signaling is responsible for cAMP-dependent defects in neuron function and learning. Collectively, these results establish defective dopaminergic function as a contributing factor underlying impaired spatial learning and memory in children and adults with NF1, and support the use of treatments that restore normal dopamine homeostasis for select individuals.

Low-level activation of N-methyl-d-aspartate receptors (NMDARs) results in a decrease in the ability of tetanic stimulation to induce long-term potentiation (LTP). This NMDAR-mediated LTP inhibition is observed with low micromolar concentrations of NMDA or chelation of ambient extracellular zinc. In rat hippocampal slices, we examined whether LTP inhibition by 1 muM NMDA and zinc chelation share common mechanisms. We found that both forms of LTP inhibition involve nitric oxide (NO) synthase (NOS) and calcineurin. Furthermore, both forms of LTP inhibition are overcome by block of p38 mitogen-activated protein kinase (MAPK), but not by inhibition of extracellular signal-regulated kinase 1/2 or c-Jun-N-terminal kinase. A p38 antagonist also overcame the block of LTP by sodium nitroprusside, an agent that releases NO, suggesting that NO release occurs upstream of MAPK activation. Despite the involvement of p38 MAPK in NMDAR-mediated LTP inhibition, p38 antagonism did not enhance LTP induction in response to weak tetanic stimulation under baseline conditions. These results indicate that p38 MAPK is part of a complex NMDAR-driven signaling pathway involving calcineurin and NO that helps to regulate synaptic plasticity in the CA1 region.

We previously found that ethanol has complex effects on hippocampal synaptic plasticity, inhibiting long-term potentiation (LTP) and long-term depression by different mechanisms. The block of long-term depression appears to be mediated by effects on N-methyl-d-aspartate receptors, whereas the block of LTP involves augmented inhibition via gamma-aminobutyric acid-A receptors (GABA(A)Rs). To pursue factors contributing to effects on LTP, we examined the ability of various concentrations of ethanol to block LTP in the CA1 region of rat hippocampal slices. Complete LTP block required 60 mm ethanol. LTP block was enhanced at lower ethanol concentrations in the presence of (3alpha5alpha)-3-hydroxypregnan-20-one, a GABA(A)R-potentiating neurosteroid, suggesting that neurosteroids may be important contributors to the effects of ethanol on LTP. Consistent with this, we found that block of LTP by 60 mm ethanol was overcome by coadministration of a cyclodextrin that binds and removes lipophilic neurosteroids. More specifically, treatment of slices with finasteride, an agent that inhibits the synthesis of 5alpha-reduced neurosteroids, or with an agent that inhibits the effects of 5alpha-reduced neurosteroids on GABA(A)Rs overcame the effects of 60 mm ethanol on LTP. Taken together, these results indicate that acute production of GABA(A)R-enhancing neurosteroids plays a key role in mediating the effects of ethanol on LTP.

Purpose: We investigated whether artificial aqueous humours are adequate incubation media compared with artificial cerebrospinal fluid (aCSF), and evaluated the retinal toxicity of two vital stains − trypan blue (TB) and indocyanine green (ICG) − and triamcinolone acetonide (TA) using isolated rat retinas incubated in artificial aqueous humours. Methods: In experiment 1, retinal segments were isolated and incubated in aCSF, BSS plus®, Opeguard® Neo Kit, or phosphate-buffered saline (PBS). In experiment 2, retinal tissues were exposed to one of the agents and incubated in BSS plus®. Retinal damage was assessed by morphological examination and biochemical assay, which measured lactate dehydrogenase (LDH) in the medium once every hour. Results: In experiment 1, BSS plus® was confirmed as a suitable incubation medium. In experiment 2, there were no significant changes in the retinas exposed to TB or TA. Tissues exposed to ICG showed damage in every retinal layer and significantly higher release of LDH. Conclusion: Exposure to ICG caused retinal damage in isolated rat retina tissue in our experimental model (in vitro).

Lactoylglutathione lyase (GLO1), a ubiquitously expressed methylglyoxal (MG) detoxification enzyme, is implicated in the progression of various human malignant diseases. However, the role of GLO1 in the development or progression of murine fibrosarcoma is still unclear. We performed proteomic analysis to identify differences in the intracellular proteins of the regressive tumor cell line QR-32 and the inflammatory cell-promoting progressive tumor cell line QRsP-11 of murine fibrosarcoma by 2DE combined with MS. Seven upregulated proteins were identified in QRsP-11 compared to QR-32 cells, namely, GLO1, annexin A1, adenylate kinase isoenzyme 1, transcription factor BTF3, myosin light polypeptide 6, low molecular weight phosphotyrosine protein phosphatase and nucleoside diphosphate kinase B. Heat shock protein beta-1 (HspB1), a methylglyoxal-adducted protein, is concomitantly over-expressed in QRsP-11 as compared to QR-32 cells. We also found out that GLO1 is translocated into the nucleus to a higher extent in QRsP-11 compared to QR-32 cells, which can be reversed by using a MEK inhibitor (U0126). Moreover, U0126 and GLO1 siRNA can inhibit cell proliferation and migration in QRsP-11 cells. Our data suggest that overexpression and nuclear translocation of GLO1 might be associated with tumor progression in murine fibrosarcoma.