Control of Glutamate Transport by Extracellular Potassium: Basis for a Negative Feedback on Synaptic Transmission.

Glutamate and K+, both released during neuronal firing, need to be tightly regulated to ensure accurate synaptic transmission. Extracellular glutamate and K+ ([K+]o) are rapidly taken up by glutamate transporters and K+-transporters or channels, respectively. Glutamate transport includes the exchange of one glutamate, 3 Na+, and one proton, in exchange for one K+. This K+ efflux allows the glutamate binding site to reorient in the outwardly facing position and start a new transport cycle. Here, we demonstrate the sensitivity of the transport process to [K+]o changes. Increasing [K+]o over the physiological range had an immediate and reversible inhibitory action on glutamate transporters. This K+-dependent transporter inhibition was revealed using microspectrofluorimetry in primary astrocytes, and whole-cell patch-clamp in acute brain slices and HEK293 cells expressing glutamate transporters. Previous studies demonstrated that pharmacological inhibition of glutamate transporters decreases neuronal transmission via extrasynaptic glutamate spillover and subsequent activation of metabotropic glutamate receptors (mGluRs). Here, we demonstrate that increasing [K+]o also causes a decrease in neuronal mEPSC frequency, which is prevented by group II mGluR inhibition. These findings highlight a novel, previously unreported physiological negative feedback mechanism in which [K+]o elevations inhibit glutamate transporters, unveiling a new mechanism for activity-dependent modulation of synaptic activity

Have a safe trip: An investigation of rituals and sanctions surrounding LSD use

There is little recent literature which identifies social controls operating among illicit drug users in Perth, Western Australia. This hinders understanding of the local illicit drug scene and makes the formulation of appropriate harm reduction strategies difficult. This study is a qualitative investigation of rituals and social sanctions which surround the use of Lysergic Acid Diethylamide (LSD). The research describes these rituals and sanctions, and examines their various functions for eight experienced users. The research adopted elements of a phenomenological approach, using in-depth semi-structured interviews to elicit a description of users\u27 subjective experiences with LSD, and Colaizzi\u27s (1978) phenomenological analysis method to probe the data for typical structures and \u27essences\u27. Credibility and validity are achieved through the use of data triangulation, participant verification, and a clearly identifiable audit trail. The results suggest that rituals and sanctions surrounding informants\u27 use of LSD are intertwined and serve a number of important functions. These include governing use through the reduction of harms and risks associated with LSD use and the maximising of pleasurable and beneficial elements of the experience. Users achieve this through the imposition of order, which is learned and practised in the social setting. Rituals and sanctions are integrated into the life of the LSD-using peer group, and have social meaning. Results indicate that the array of social controls which govern participants\u27 use of LSD have varying degrees of success. A dialectical relationship between rituals and sanctions and the social setting exists, with both adapting to the presence and impact of the other. The outcome of this is that rituals and sanctions are modified, corrected and strengthened by their own outcomes. Results also challenge popular constructions of illicit drug users which dominate public discourse. The implications for harm reduction, drug education and future research are discussed

The routines and rituals of a design and technology classroom: An ethnographic study

This research examines questions and issues raised from an ethnographic study of a secondary design and technology classroom. A critical ethnographic methodology was employed to explore the \u27way of life\u27 in design and technology and examine how aspects of this micro-culture impact on teaching and learning. This ethnographic account includes description and discussion of four significant aspects of design and technology culture. The first examines the predominant masculine culture within this classroom and the subject area at large. The second is the story of four girls and their perceived alienation and exclusion from the dominance of a boy subject . Third is an account of both internal and external perceptions of the status of design and technology compared to the more traditionally liberal pursuits. The final point is an analysis of how aspects of the culture within this classroom impact teaching and learning. The implications of aspects of this classroom culture are discussed

The routines and rituals of a design and technology classroom: an ethnographic study

This study outlines issues identified from an ethnographic study of an Australian secondary design and technology classroom. The aim of the study was to explore the features and characteristics of this classroom and examine how aspects of this micro-culture impact on teaching and learning. Of particular concern is discussion of an ethnographic methodology, and the subsequent product of that methodology, for examining and communicating aspects of design and technology culture. An account of this design and technology classroom includes description and discussion of four significant aspects of this culture. The first examines the predominant masculine culture within this learning area. The second is the story of four girls and their perceived exclusion from right of passage into design and technology. Third is an account of the various perceptions of status in design and technology compared with the more traditionally liberal pursuits. The final point looks at the impact of the historical genesis of design and technology on this culture. Implications of aspects of this culture are discussed, as is the benefit of commencing an ethnography of design and technology education. The paper highlights the need to address this culture in order to understand its impact on classroom life

From Cultured Rodent Neurons to Human Brain Tissue: Model Systems for Pharmacological and Translational Neuroscience.

To investigate the enormous complexity of the functional and pathological brain there are a number of possible experimental model systems to choose from. Depending on the research question choosing the appropriate model may not be a trivial task, and given the dynamic and intricate nature of an intact living brain several models might be needed to properly address certain questions. In this review, we aim to provide an overview of neural cell and tissue culture, reflecting on historic methodological milestones and providing a brief overview of the state-of-the-art. We additionally present an example of an effective model system pipeline, composed of dissociated mouse cultures, organotypics, acute mouse brain slices, and acute human brain slices, in that order. The sequential use of these four model systems allows a balance and progression from experimental control to human applicability, and provides a meta-model that can help validate basic research findings in a translational setting. We then conclude with a few remarks regarding the necessity of an integrated approach when performing translational and neuropharmacological studies

Extracellular Potassium and Glutamate Interact To Modulate Mitochondria in Astrocytes.

Astrocytes clear glutamate and potassium, both of which are released into the extracellular space during neuronal activity. These processes are intimately linked with energy metabolism. Whereas astrocyte glutamate uptake causes cytosolic and mitochondrial acidification, extracellular potassium induces bicarbonate-dependent cellular alkalinization. This study aimed at quantifying the combined impact of glutamate and extracellular potassium on mitochondrial parameters of primary cultured astrocytes. Glutamate in 3 mM potassium caused a stronger acidification of mitochondria compared to cytosol. 15 mM potassium caused alkalinization that was stronger in the cytosol than in mitochondria. While the combined application of 15 mM potassium and glutamate led to a marked cytosolic alkalinization, pH only marginally increased in mitochondria. Thus, potassium and glutamate effects cannot be arithmetically summed, which also applies to their effects on mitochondrial potential and respiration. The data implies that, because of the nonlinear interaction between the effects of potassium and glutamate, astrocytic energy metabolism will be differentially regulated

Activation of lactate receptor HCAR1 down-modulates neuronal activity in rodent and human brain tissue.

Lactate can be used by neurons as an energy substrate to support their activity. Evidence suggests that lactate also acts on a metabotropic receptor called HCAR1, first described in the adipose tissue. Whether HCAR1 also modulates neuronal circuits remains unclear. In this study, using qRT-PCR, we show that HCAR1 is present in the human brain of epileptic patients who underwent resective surgery. In brain slices from these patients, pharmacological HCAR1 activation using a non-metabolized agonist decreased the frequency of both spontaneous neuronal Ca <sup>2+</sup> spiking and excitatory post-synaptic currents (sEPSCs). In mouse brains, we found HCAR1 expression in different regions using a fluorescent reporter mouse line and in situ hybridization. In the dentate gyrus, HCAR1 is mainly present in mossy cells, key players in the hippocampal excitatory circuitry and known to be involved in temporal lobe epilepsy. By using whole-cell patch clamp recordings in mouse and rat slices, we found that HCAR1 activation causes a decrease in excitability, sEPSCs, and miniature EPSCs frequency of granule cells, the main output of mossy cells. Overall, we propose that lactate can be considered a neuromodulator decreasing synaptic activity in human and rodent brains, which makes HCAR1 an attractive target for the treatment of epilepsy