26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15–20 July 2017

This work was produced as part of the activities of FAPESP Research,\ud Disseminations and Innovation Center for Neuromathematics (grant\ud 2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud supported by a CNPq fellowship (grant 306251/2014-0)

Synaptic Information Transmission in a Two-State Model of Short-Term Facilitation

Action potentials (spikes) can trigger the release of a neurotransmitter at chemical synapses between neurons. Such release is uncertain, as it occurs only with a certain probability. Moreover, synaptic release can occur independently of an action potential (asynchronous release) and depends on the history of synaptic activity. We focus here on short-term synaptic facilitation, in which a sequence of action potentials can temporarily increase the release probability of the synapse. In contrast to the phenomenon of short-term depression, quantifying the information transmission in facilitating synapses remains to be done. We find rigorous lower and upper bounds for the rate of information transmission in a model of synaptic facilitation. We treat the synapse as a two-state binary asymmetric channel, in which the arrival of an action potential shifts the synapse to a facilitated state, while in the absence of a spike, the synapse returns to its baseline state. The information bounds are functions of both the asynchronous and synchronous release parameters. If synchronous release facilitates more than asynchronous release, the mutual information rate increases. In contrast, short-term facilitation degrades information transmission when the synchronous release probability is intrinsically high. As synaptic release is energetically expensive, we exploit the information bounds to determine the energy–information trade-off in facilitating synapses. We show that unlike information rate, the energy-normalized information rate is robust with respect to variations in the strength of facilitation

Short-term synaptic depression can increase the rate of information transfer at a release site

The release of neurotransmitters from synapses obeys complex and stochastic dynamics. Depending on the recent history of synaptic activation, many synapses depress the probability of releasing more neurotransmitter, which is known as synaptic depression. Our understanding of how synaptic depression affects the information efficacy, however, is limited. Here we propose a mathematically tractable model of both synchronous spike-evoked release and asynchronous release that permits us to quantify the information conveyed by a synapse. The model transits between discrete states of a communication channel, with the present state depending on many past time steps, emulating the gradual depression and exponential recovery of the synapse. Asynchronous and spontaneous releases play a critical role in shaping the information efficacy of the synapse. We prove that depression can enhance both the information rate and the information rate per unit energy expended, provided that synchronous spike-evoked release depresses less (or recovers faster) than asynchronous release. Furthermore, we explore the theoretical implications of short-term synaptic depression adapting on longer time scales, as part of the phenomenon of metaplasticity. In particular, we show that a synapse can adjust its energy expenditure by changing the dynamics of short-term synaptic depression without affecting the net information conveyed by each successful release. Moreover, the optimal input spike rate is independent of the amplitude or time constant of synaptic depression. We analyze the information efficacy of three types of synapses for which the short-term dynamics of both synchronous and asynchronous release have been experimentally measured. In hippocampal autaptic synapses, the persistence of asynchronous release during depression cannot compensate for the reduction of synchronous release, so that the rate of information transmission declines with synaptic depression. In the calyx of Held, the information rate per release remains constant despite large variations in the measured asynchronous release rate. Lastly, we show that dopamine, by controlling asynchronous release in corticostriatal synapses, increases the synaptic information efficacy in nucleus accumbens

Changes in essential oil content of different organs of dill genotypes in response to water deficit

A split plot experiment (based on RCB design) with four replications was conducted in 2014, to evaluate the effects of different irrigation treatments (I1, I2, I3 and I4: irrigation after 70, 100, 130 and 160 mm evaporation, respectively) on essential oil content of dill (Anethum graveolens L.) organs in two genotypes (Local and Mammoth). Irrigation treatments and genotypes were allocated to the main and sub-plots, respectively. Essential oil percentage of dill organs increased, but their essence yield decreased as water deficit severed. Mammoth had the highest essential oil percentage in all organs, but essential oil yield of vegetative organs and flowers of the local genotype was much more than that of mammoth genotype. However, the difference in essence yield of seeds between two genotypes was not significant. The highest essential oil percentage and yield under all irrigation intervals were obtained from seeds, followed by flowers and vegetative organs. It was concluded that seeds and flowers are the most beneficial organs of dill, regarding essential oil production, although dill is largely used as a vegetable

Steroid in the treatment of outpatient COVID-19: A multicenter randomized controlled trial

Background: Early treatment of COVID-19 patients could reduce hospitalization and death. The effect of corticosteroids in the outpatient setting is still unknown. This study aimed to determine the effect of corticosteroids in the prevention of hospitalization of nonsevere cases. Materials and Methods: This study is a multicenter randomized controlled trial. Seventy five nonsevere COVID-19 patients presented between days 7 and 14 of their symptoms received either prednisolone or placebo. The primary outcome was hospitalization. The study protocol was registered in the Iranian Registry of Clinical Trials on December 2, 2020 (IRCT20171219037964N2). Results: Although the rate of hospitalization in the prednisolone group was higher than the placebo group (10.8% vs. 7.9%, respectively), it was not statistically significant (P value.,6). One patient in each group reported an adverse event and withdrew the medication. Conclusion: Considering the null effect of corticosteroids in the prevention of hospitalization in outpatient settings, it is suggested not to consider corticosteroids for outpatient treatment