Priming stimulation modifies synaptic plasticity in the perforant path of hippocampal slice in rat

Objective The potential of all central nervous system synapses to exhibit long term potentiation （LTP） or long term depression （LTD） is subject to modulation by prior synaptic activity, a higher-order form of plasticity that has been termed metaplasticity. This study is designed to examine the plasticity and metaplasticity in the lateral perforant path of rat. Methods Field potential was measured with different priming and conditioning stimulation protocols. Results Ten-hertz priming, which does not affect basal synaptic transmission, caused a dramatic reduction in subsequent LTP at lateral perforant path synapses in vitro, and the reduced LTP lasted for at least 2 h. The LTD was unaffected. The reduction of LTP in the lateral perforant path was also readily induced by applying priming antidromically at the mossy fibers. Conclusion Priming with 10 Hz, which is within a frequency range observed during physiological activity, can cause potent, long-lasting inhibition of LTP, but not LTD. This form of metaplasticity adds a layer of complexity to the activity-dependent modification of synapses within the dentate gyrus.

Newborns' sleep-wake cycle development on amplitude integrated electroencephalography

Background:To observe the development of neonatal sleep among healthy infants of different conceptional age(CA)by analyzing the amplitude-integrated electroencephalography(aEEG)of their sleep-wake cycles(SWC).Methods:Bedside aEEG monitoring was carried out for healthy newborns from 32 to 46 weeks CA between September 1,2011 and August 30,2012.For each aEEG tracing,mean duration of every complete SWC,number of SWC repetition within 12 hours,mean duration of each narrow and broadband of SWC,mean voltage of the upper edge and lower edge of SWC,mean bandwidth of SWC were counted and calculated.Analysis of the correlations between voltages or bandwidth of SWC and CA was performed to assess the developmental changes of central nervous system of newborns with different CA.Results:The SWC of different CA on aEEG showed clearly identifiable trend after 32 weeks of CA.The occurrence of SWC gradually increases from preterm to post-term infants;term infants had longer SWC duration.The voltage of upper edge of the broadband decreased at 39 weeks,while the lower edge voltage increases and the bandwidth of broadband declined along with the growing CA.The upper edge of the narrowband dropped while the lower edge rised gradually,especially in preterm stage.The width of the narrowband narrowed down while CA increased.Conclusions:The SWC on aEEG of 32-46 weeks infants showed a continuous,dynamic and developmental progress.The appearance of SWC and the narrowing bandwidth of narrowband is the main indicator to identify the CA-dependent SWC from the preterm to the late preterm period.The lower edge of the broadband identifi es the term to post-term period.