Carbon nanotubes exert basic excitatory enhancement in rat brain slices

The insecticide esfenvalerate modulates neuronal excitability in mammalian central nervous system in vitro

Pyrethroids are neurotoxic insecticides showing significant selective toxicity on insects over mammals, but effects on mammalian nervous system are not negligible. These substances act on the voltage-gated sodium channel, prolonging the duration of the open state. The present study focused on the effect of the pyrethroid esfenvalerate on the excitability of neuronal networks in vitro. From isolated rat brain slices, neocortical and hippocampal evoked field potentials were recorded; four concentrations (5-40μM) of esfenvalerate were tested using in vitro administration of the commercial product Sumi-Alpha 5 EC^®. Basic excitability and short- and long-term synaptic plasticity were studied. Application of the lowest concentration elicited epileptiform discharges in neocortex, while the highest concentration exerted a strong inhibitory effect on the excitability of both brain areas. The amplitude of population spikes in hippocampal slices was decreased by all applied concentrations. Significant decrease in basic excitability was accompanied by increase of paired-pulse facilitation in hippocampus and decreased efficacy of the development of long-term potentiation in both regions. Pyrethroids have been scarcely studied on brain slices so far, but our results are in concordance with literary data obtained on other in vitro neuronal test systems. It has been described previously that lower concentrations of pyrethroids lead to overexcitation of neurons and repetitive firing (which is in the background of hyperexcitatory symptoms occurring in case of in vivo exposure). Higher concentrations, however, may lead to depolarization block and to inhibition of neuronal firing.

Repairing Peripheral Nerves: Is there a Role for Carbon Nanotubes?

Peripheral nerve injury continues to be a major global health problem that can result in debilitating neurological deficits and neuropathic pain. Current state-of-the-art treatment involves reforming the damaged nerve pathway using a nerve autograft. Engineered nerve repair conduits can provide an alternative to the nerve autograft avoiding the inevitable tissue damage caused at the graft donor site. Commercially available nerve repair conduits are currently only considered suitable for repairing small nerve lesions; the design and performance of engineered conduits requires significant improvements to enable their use for repairing larger nerve defects. Carbon nanotubes (CNTs) are an emerging novel material for biomedical applications currently being developed for a range of therapeutic technologies including scaffolds for engineering and interfacing with neurological tissues. CNTs possess a unique set of physicochemical properties that could be useful within nerve repair conduits. This progress report aims to evaluate and consolidate the current literature pertinent to CNTs as a biomaterial for supporting peripheral nerve regeneration. The report is presented in the context of the state-of-the-art in nerve repair conduit design; outlining how CNTs may enhance the performance of next generation peripheral nerve repair conduits.