Enriched environment treatment restores impaired hippocampal synaptic plasticity and cognitive deficits induced by prenatal chronic stress

Prenatal stress can cause long-term effects on cognitive functions in offspring. Hippocampal synaptic plasticity, believed to be the mechanism underlying certain types of learning and memory, and known to be sensitive to behavioral stress, can be changed

Chronic Morphine Treatment Impaired Hippocampal Long-Term Potentiation and Spatial Memory via Accumulation of Extracellular Adenosine Acting on Adenosine A(1) Receptors

Chronic exposure to opiates impairs hippocampal long-term potentiation (LTP) and spatial memory, but the underlying mechanisms remain to be elucidated. Given the well known effects of adenosine, an important neuromodulator, on hippocampal neuronal excitability and synaptic plasticity, we investigated the potential effect of changes in adenosine concentrations on chronic morphine treatment-induced impairment of hippocampal CA1 LTP and spatial memory. We found that chronic treatment in mice with either increasing doses (20-100 mg/kg) of morphine for 7 d or equal daily dose (20 mg/kg) of morphine for 12 d led to a significant increase of hippocampal extracellular adenosine concentrations. Importantly, we found that accumulated adenosine contributed to the inhibition of the hippocampal CA1 LTP and impairment of spatial memory retrieval measured in the Morris water maze. Adenosine A(1) receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine significantly reversed chronic morphine-induced impairment of hippocampal CA1 LTP and spatial memory. Likewise, adenosine deaminase, which converts adenosine into the inactive metabolite inosine, restored impaired hippocampal CA1 LTP. We further found that adenosine accumulation was attributable to the alteration of adenosine uptake but not adenosine metabolisms. Bidirectional nucleoside transporters (ENT2) appeared to play a key role in the reduction of adenosine uptake. Changes in PKC-alpha/beta activity were correlated with the attenuation of the ENT2 function in the short-term (2 h) but not in the long-term (7 d) period after the termination of morphine treatment. This study reveals a potential mechanism by which chronic exposure to morphine leads to impairment of both hippocampal LTP and spatial memory.

汉字阅读中的字形、字音、字义及频率效应的研究

Unlike alphabetic languages, Chinese language is ideographical writing system. Each Chinese character is single-syllable and usually has a direct meaning. So Chinese characters are a kind of valuable experimental material used for research on reading and comparisons of the reading mechanism of different language. In this paper, the normal persons and the patients with semantic dementia were respectively scheduled for two parts of experimental studies on the orthographic, phonologic, semantic and frequency effects of reading of Chinese characters. The Stroop-like character-picture interference experimental paradigm was used to investigate the orthographic, phonologic, semantic and frequency effects of Chinese characters on picture naming when they were presented with pictures to normal persons. The results indicated that the orthographic facilitation effect, phonologic facilitation effect, and semantic interference effect occurred at different SOA values. The orthographic and phonologic facilitation effects were independent. It was for the first time shown that the interaction between orthographic variable and semantic variable occurred when the high-frequency Chinese characters were read. Phonologic representation was activated quicker than semantic representation, by comparison of their SOA. Generally, it means that there is reading without meaning in Chinese character among the normal persons. The orthographic, phonologic, semantic, frequency and concrete effects of Chinese characters were further investigated among the dementia patients with DAT(dementia of Alzheimer's type disease) or CVA or both. They all have an impaired semantic memory. The results showed that patients with dementia could read the names of the pictures aloud while they could not name them or match them with a right character correctly. This is reading impairment without meaning in Chinese among the dementia patients. Meanwhile, they had a selective reading impairment and more LARC(a legitimate alternative reading of components) mistakes especially when reading low-frequency irregular, low-frequency inconsistent and abstract Chinese characters. With the patients' semantic impairment developed, their ability to read the pictures names would remain whereas their ability to read low-frequency irregular and low-frequency inconsistency Chinese characters was reduced. These results indicated that low-frequency irregular Chinese characters can be read correctly only when it is supported by their semantic information. Based on the above results of reading without meaning and of reading of low-frequency irregular Chinese characters supported by their semantic information, it is reasonable to suggest that at least two routes are involved in the process of reading Chinese characters. They are direct phonologic route and indirect semantic route; moreover, the two routes are independent.