Journal of neuroscience methods
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J. Neurosci. Methods · Sep 2006
Reversible vagal blockade in conscious rats using a targeted delivery device.
Reversible methods of nerve blockade greatly aid neurophysiological and behavioral studies. We have developed an implantable device for the local delivery of anesthetics to the area surrounding the vagal nerve in rats. The device consists of a thick silicone tube for insulating the nerves from the surrounding tissue, and a thin silicone tube for the infusion of anesthetics into the insulating tube. ⋯ Electrical stimulation of the right vagus nerve in conscious rats increased arterial pressure while decreasing heart rate. The local blockade of afferent fibers abolished the arterial pressure response but preserved the bradycardic response to vagal nerve stimulation. The targeted delivery device was useful for reversible vagal blockade in conscious rats.
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J. Neurosci. Methods · Jul 2006
Characterization of hind paw licking and lifting to noxious radiant heat in the rat with and without chronic inflammation.
The paw withdrawal latency to thermal radiant heat stimuli is a widely used nociceptive measure to study hyperalgesic mechanisms. In the present study, in addition to the paw withdrawal latency, two behavioral components of pain behaviors, paw licking and paw lifting have been characterized and quantified. The thermal stimuli were successively applied to the plantar surface of the rat hind paws and recorded the behavioral responses to each of the stimuli. ⋯ The paw withdrawal latency decreased in inflamed rats in comparison with control rats. These data informs that noxious radiant heat specifically evokes the frequency of paw lifting behavior in normal physiological condition, and paw licking behavior in a pathological inflammatory condition. These findings suggest that in addition to the measurement of PWL, scoring of paw licking and lifting behaviors will improve the sensitivity of this pain test.
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J. Neurosci. Methods · Jun 2006
Online detection and sorting of extracellularly recorded action potentials in human medial temporal lobe recordings, in vivo.
Understanding the function of complex cortical circuits requires the simultaneous recording of action potentials from many neurons in awake and behaving animals. Practically, this can be achieved by extracellularly recording from multiple brain sites using single wire electrodes. However, in densely packed neural structures such as the human hippocampus, a single electrode can record the activity of multiple neurons. ⋯ We demonstrate the utility of the method by applying it to an extensive data set we acquired from chronically implanted depth electrodes in the hippocampus of human epilepsy patients. This dataset is particularly challenging because it was recorded in a noisy clinical environment. This method will allow the development of "closed-loop" experiments, which immediately adapt the experimental stimuli and/or tasks to the neural response observed.
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J. Neurosci. Methods · May 2006
Development of transplantable nervous tissue constructs comprised of stretch-grown axons.
Pursuing a new approach to nervous system repair, fasciculated axon tracts grown in vitro were developed into nervous tissue constructs designed to span peripheral nerve or spinal cord lesions. We optimized the newfound process of extreme axon stretch growth to maximize the number and length of axon tracts, reach an unprecedented axon growth-rate of 1cm/day, and create 5cm long axon tracts in 8 days to serve as the core component of a living nervous tissue construct. Immunocytochemical analysis confirmed that elongating fibers were axons, and that all major cytoskeletal constituents were present across the stretch-growth regions. ⋯ Alternatively, we induced axon stretch growth directly on a surgical membrane that could be removed from the elongation device, and formed into a cylindrical construct suitable for transplant. The ability to rapidly create living nervous tissue constructs that recapitulates the uniaxial orientations of the original nerve offers an unexplored and potentially complimentary direction in nerve repair. Ideally, bridging nerve damage with living axon tracts may serve to establish or promote new functional connections.
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J. Neurosci. Methods · Jan 2006
An in vitro model of traumatic brain injury utilising two-dimensional stretch of organotypic hippocampal slice cultures.
Traumatic brain injury (TBI) is caused by rapid deformation of the brain, resulting in a cascade of pathological events and ultimately neurodegeneration. Understanding how the biomechanics of brain deformation leads to tissue damage remains a considerable challenge. We have developed an in vitro model of TBI utilising organotypic hippocampal slice cultures on deformable silicone membranes, and an injury device, which generates tissue deformation through stretching the silicone substrate. ⋯ Cell damage following injury is positively correlated with strain. In conclusion, we have developed a unique in vitro model to study the effects of mechanical stimuli within a complex cellular environment that mimics the in vivo environment. We believe this model could be a powerful tool to study the acute phases of TBI and the induced cell degeneration could provide a good platform for the development of potential therapeutic approaches and may be a useful in vitro alternative to animal models of TBI.