A neural theory for counting memories

Keeping track of the number of times different stimuli have been experienced is a critical computation for behavior. Here, we propose a theoretical two-layer neural circuit that stores counts of stimulus occurrence frequencies. This circuit implements a data structure, called a count sketch, that is commonly used in computer science to maintain item frequencies in streaming data. Our first model implements a count sketch using Hebbian synapses and outputs stimulus-specific frequencies. Our second model uses anti-Hebbian plasticity and only tracks frequencies within four count categories ("1-2-3-many"), which trades-off the number of categories that need to be distinguished with the potential ethological value of those categories. We show how both models can robustly track stimulus occurrence frequencies, thus expanding the traditional novelty-familiarity memory axis from binary to discrete with more than two possible values. Finally, we show that an implementation of the "1-2-3-many" count sketch exists in the insect mushroom body

Characterization on Responsiveness of Excitatory Synaptic Transmissions to α1-Adrenoceptor Blockers in Substantia Gelatinosa Neurons Isolated From Lumbo-Sacral Level in Rat Spinal Cords

Purpose The aim of this study was to characterize the responsiveness of miniature excitatory postsynaptic currents (mEPSCs) to α1-adrenoceptor blockers in substantia gelatinosa (SG) neurons from the spinal cord to develop an explanation for the efficacy of α1-adrenoceptor blockers in micturition dysfunction. Methods Male adult Sprague-Dawley rats were used. Blind whole-cell patch-clamp recordings were performed using SG neurons in spinal cord slices. Naftopidil (100μM), tamsulosin (100μM), or silodosin (30μM), α1-adrenoceptor blockers, was perfused. The frequency of mEPSCs was recorded in an SG neuron to which the 3 blockers were applied sequentially with wash-out periods. Individual frequencies in a pair before naftopidil and tamsulosin perfusion were plotted as baseline, and the correlation between them was confirmed by Spearman correlation coefficient; linear regression was then performed. The same procedure was performed before naftopidil and silodosin perfusion. Frequencies of pairs after naftopidil and tamsulosin perfusion and after naftopidil and silodosin perfusion were similarly analyzed. The ratios of the frequencies after treatment to before were then calculated. Results After the treatments, Spearman ρ and the slope were decreased to 0.682 from 0.899 at baseline and 0.469 from 1.004 at baseline, respectively, in the tamsulosin group relative to the naftopidil group. In the silodosin group, Spearman ρ and the slope were also decreased to 0.659 from 0.889 at baseline and 0.305 from 0.989 at baseline, respectively, relative to the naftopidil group. Naftopidil significantly increased the ratio of the frequency of mEPSCs compared to tamsulosin and silodosin (P=0.015 and P=0.004, respectively). Conclusions There was a difference in responsiveness in the frequency of mEPSCs to α1-adrenoceptor blockers, with the response to naftopidil being the greatest among the α1-adrenoceptor blockers. These data are helpful to understand the action mechanisms of α1-adrenoceptor blockers for male lower urinary tract symptoms in clinical usage

Effects of High Concentrations of Naftopidil on Dorsal Root-Evoked Excitatory Synaptic Transmissions in Substantia Gelatinosa Neurons

Purpose Naftopidil ((±)-1-[4-(2-methoxyphenyl) piperazinyl]-3-(1-naphthyloxy) propan-2-ol) is prescribed in several Asian countries for lower urinary tract symptoms suggestive of benign prostatic hyperplasia. Previous animal experiments showed that intrathecal injection of naftopidil abolished rhythmic bladder contraction in vivo. Naftopidil facilitated spontaneous inhibitory postsynaptic currents in substantia gelatinosa (SG) neurons in spinal cord slices. These results suggest that naftopidil may suppress the micturition reflex at the spinal cord level. However, the effect of naftopidil on evoked excitatory postsynaptic currents (EPSCs) in SG neurons remains to be elucidated. Methods Male Sprague-Dawley rats at 6 to 8 weeks old were used. Whole-cell patch-clamp recordings were made using SG neurons in spinal cord slices isolated from adult rats. Evoked EPSCs were analyzed in Aδ or C fibers. Naftopidil or prazosin, an α1-adrenoceptor blocker, was perfused at 100 μM or 10 μM, respectively. Results Bath-applied 100 μM naftopidil significantly decreased the peak amplitudes of Aδ and C fiber-evoked EPSCs to 72.0%±7.1% (n=15) and 70.0%±5.5% (n=20), respectively, in a reversible and reproducible manner. Bath application of 10μM prazosin did not inhibit Aδ or C fiber-evoked EPSCs. Conclusions The present study suggests that a high concentration of naftopidil reduces the amplitude of evoked EPSCs via a mechanism that apparently does not involve α1-adrenoceptors. Inhibition of evoked EPSCs may also contribute to suppression of the micturition reflex, together with nociceptive stimulation

X-ray dose reduction using additional copper filtration for abdominal digital radiography: Evaluation using signal difference-to-noise ratio

Purpose: X-ray dose reduction using additional copper filters (Cu-filters) for abdominal general radiography was indicated in a report using a simulation study. We validated the dose reduction effects using a clinical digital radiography system equipped with an indirect-type CsI detector and an automatic Cu-filter insertion function. Methods: The image qualities were evaluated using signal difference-to-noise ratio (SDNR) for different radiation qualities with and without Cu-filters for a 20-cm acrylic phantom. Acrylic and bone equivalent material plates were used for contrast measurements. The dose reduction using Cu-filters was estimated from the ratios of the SDNR2 values. Results: For the same entrance surface dose (ESD), Cu-filters with 0.1- and 0.2-mm thicknesses increased the image quality as evaluated by SDNR2 and the estimated dose reduction without degrading the image quality. For the acrylic contrast, the dose reductions with the 0.1- and 0.2-mm-thick Cu-filters were approximately 30% and 44% at 70kV and 29% and 35% at 80kV, respectively. For the bone contrast, the reduction rates were slightly reduced. Conclusions: We validated the dose reduction capability of additional Cu-filters without degrading the image quality for abdominal radiography. The estimated entrance surface dose reductions of the Cu-filters were approximately 30-40% and 20-30% for the acrylic and bone contrasts, respectively, and effective dose reductions for acrylic were nearly half of those for ESD. At these reduced dose conditions, the current time product values needed to be increased by factors of 1.4 and 1.8 for the 0.1- and 0.2-mm-thick Cu-filters, respectively. © 2017 Associazione Italiana di Fisica Medica.Embargo Period 12 month

First Synthesis of a Natural Neopterin Glycoside: 3'-O-(β-D-Glucopyranosyluronic acid)neopterin

1',2'-Di-O-acetyl-N2-(N,N-dimethylaminomethylene)-3-[2-(4-nitrophenyl)ethyl]neopterin (1) was prepared from neopterin in 5 steps. Glycosylation of 1 with methyl 2,3,4-tri-O-benzoyl-α-D-glucopyranosyluronate bromide in the presence of silver triflate and tetramethylurea afforded the corresponding 3'-O-(methyl β-D-glucopyranosyluronate) neopterin derivative (2) in 64% yield. The first synthesis of 3'-O-(β-D-glucopyranosyluronic acid)neopterin was achieved by successive removal (4 steps) of the protecting groups of 2

Control of peroxyoxalate chemiluminescence by nitrogen-containing ligand quenching: turning off and on by ligand-metal ion host-guest interactions

ArticleTETRAHEDRON. 67(36):6927-6933 (2011)journal articl