Burst predicting neurons survive an in vitro glutamate injury model of cerebral ischemia

A high-density multi-electrode platform examining the effects of radiation on in vitro cortical networks

Radiation therapy and stereotactic radiosurgery are common treatments for brain malignancies. However, the impact of radiation on underlying neuronal circuits is poorly understood. In the prefrontal cortex (PFC), neurons communicate via action potentials that control cognitive processes, thus it is important to understand the impact of radiation on these circuits. Here we present a novel protocol to investigate the effect of radiation on the activity and survival of PFC networks in vitro. Escalating doses of radiation were applied to PFC slices using a robotic radiosurgery platform at a standard dose rate of 10 Gy/min. High-density multielectrode array recordings of radiated slices were collected to capture extracellular activity across 4,096 channels. Radiated slices showed an increase in firing rate, functional connectivity, and complexity. Graph-theoretic measures of functional connectivity were altered following radiation. These results were compared to pharmacologically induced epileptic slices where neural complexity was markedly elevated, and functional connections were strong but remained spatially focused. Finally, propidium iodide staining revealed a dose-dependent effect of radiation on apoptosis. These findings provide a novel assay to investigate the impacts of clinically relevant doses of radiation on brain circuits and highlight the acute effects of escalating radiation doses on PFC neurons.

Neuronal Cultures: Exploring Biophysics, Complex Systems, and Medicine in a Dish

Neuronal cultures are one of the most important experimental models in modern interdisciplinary neuroscience, allowing to investigate in a control environment the emergence of complex behavior from an ensemble of interconnected neurons. Here, I review the research that we have conducted at the neurophysics laboratory at the University of Barcelona over the last 15 years, describing first the neuronal cultures that we prepare and the associated tools to acquire and analyze data, to next delve into the different research projects in which we actively participated to progress in the understanding of open questions, extend neuroscience research on new paradigms, and advance the treatment of neurological disorders. I finish the review by discussing the drawbacks and limitations of neuronal cultures, particularly in the context of brain-like models and biomedicine.

Resilience of network activity in preconditioned neurons exposed to 'stroke-in-a-dish' insults

Exposing cultured cortical neurons to stimulatory agents - the K⁺ channel blocker 4-aminopyridine (4-ap), and the GABA_A receptor antagonist bicuculline (bic) - for 48 h induces down-regulated synaptic scaling, and preconditions neurons to withstand subsequent otherwise lethal 'stroke-in-a-dish' insults; however, the degree to which usual neuronal function remains is unknown. As a result, multi-electrode array and patch-clamp electrophysiological techniques were employed to characterize hallmarks of spontaneous synaptic activity over a 12-day preconditioning/insult experiment. Spiking frequency increased 8-fold immediately upon 4-ap/bic treatment but declined within the 48 h treatment window to sub-baseline levels that persisted long after washout. Preconditioning resulted in key markers of network activity - spiking frequency, bursting and avalanches - being impervious to an insult. Surprisingly, preconditioning resulted in higher peak NMDA mEPSC amplitudes, resulting in a decrease in the ratio of AMPA:NMDA mEPSC currents, suggesting a relative increase in synaptic NMDA receptors. An investigation of a broad mRNA panel of excitatory and inhibitory signaling mediators indicated preconditioning rapidly up-regulated GABA synthesis (GAD67) and BDNF, followed by up-regulation of neuronal activity-regulated pentraxin and down-regulation of presynaptic glutamate release (VGLUT1). Preconditioning also enhanced surface expression of GLT-1, which persisted following an insult. Overall, preconditioning resulted in a reduced spiking frequency which was impervious to subsequent exposure to 'stroke-in-a-dish' insults, a phenotype initiated predominantly by up-regulation of inhibitory neurotransmission, a lower neuronal postsynaptic AMPA: NMDA receptor ratio, and trafficking of GLT-1 to astrocyte plasma membranes.

In Vitro Models as a Platform to Investigate Traumatic Brain Injury

Traumatic Brain Injury (TBI) remains a significant cause of mortality and morbidity, affecting individuals of all age groups. Much remains to be learned about its complex pathophysiology, with a view to designing effective neuroprotective strategies to protect sublethally injured brain tissue that would otherwise die in secondary injury processes. Experimental in vivo models offer the potential to study TBI in the laboratory, however, treatments that were neuroprotective in animals have, thus far, largely failed to translate in human clinical studies. In vitro models of neurotrauma can be used to study specific pathophysiological cascades — individually and without confounding factors — and to test potential neuroprotective strategies. These in vitro models include transection, compression, barotrauma, acceleration, hydrodynamic, chemical injury and cell-stretch methodologies. Various cell culture systems can also be utilised, including brain-on-a-chip, immortalised cell lines, primary cultures, acute preparations and organotypic cultures. Potential positive outcomes of the increased use of in vitro platforms to study TBI would be the refinement of in vivo experiments, as well as enhanced translation of the results into clinically meaningful neuroprotective strategies for the future. In addition, the replacement of in vivo experiments by suitable in vitro studies would lead to a welcome reduction in the numbers of animal procedures in this ethically-challenging field.