Neuroscience and biobehavioral reviews
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CT (C tactile) afferents are a distinct type of unmyelinated, low-threshold mechanoreceptive units existing in the hairy but not glabrous skin of humans and other mammals. Evidence from patients lacking myelinated tactile afferents indicates that signaling in these fibers activate the insular cortex. ⋯ CT fiber activation may also have a role in pain inhibition. This review outlines the growing evidence for unique properties and pathways of CT afferents.
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Decades of pain research have succeeded in elucidating complex mechanisms of acute activation and chronic sensitization of nociceptors leading to pain. In contrast, itch conditions have received less attention and even basic mechanisms for the induction of itch are still unclear. In this review we describe itch-specific pathways, but also evidence for a modified pattern theory of pruritus offering independent mechanisms for the itch induction. ⋯ However, concerning mechanisms of sensitization to itch or pain, surprisingly similar patterns have been observed lately in both inflamed tissue and in the spinal cord. These similarities open up two highly interesting perspectives: the role of well established analgesic therapeutic concepts can be validated in chronic itch conditions and on the other hand investigations of sensitization in easily accessible pruritic skin may help to validate concepts of nociception in humans. These perspectives illustrate that itch and pain research no longer follows separate paths, but can be advantageously interconnected.
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Neurosci Biobehav Rev · Jan 2010
ReviewA critical review of human endotoxin administration as an experimental paradigm of depression.
The syndrome called depression may represent the common final pathway at which different aetiopathogenic processes converge. One such aetiopathogenic process is innate immune system activation. Some depressed patients have increased levels of inflammatory cytokines and other immunologic abnormalities. ⋯ A new approach to depression research would be to use immune stimuli to elicit depressive symptoms in humans. Here we review each of the symptoms elicited in humans by endotoxin administration, and compare this model to two other immune depression paradigms: interferon-alpha treatment and typhoid vaccine administration, to assess to what degree endotoxin administration represents a valid model of immune depression. We also review corresponding behavioral changes in rodents and the potential molecular pathways through which immune system activation produces each symptom.
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Neurosci Biobehav Rev · Jul 2009
ReviewDeep brain stimulation, vagal nerve stimulation and transcranial stimulation: An overview of stimulation parameters and neurotransmitter release.
Neurological disorders are among the most challenging medical problems faced by science today. To treat these disorders more effectively, new technologies are being developed by reviving old ideas such as brain stimulation. This review aims to compile stimulation techniques that are currently in use to explore or treat neurological disorders. ⋯ Scientific and clinical applications have largely preceded the development of extensive animal models, presenting a challenge for researchers. This has left researchers with information on alleviating symptoms in humans but without solid research as to the mechanisms and neurobiological effects of the devices. This review combines stimulation parameters developed in animal models and stimulation techniques used in human treatment; thus, resulting in a greater understanding of the mechanisms and neurobiological effects of neuromodulation devices.
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Neurosci Biobehav Rev · Jun 2009
ReviewRodent models of insomnia: a review of experimental procedures that induce sleep disturbances.
Insomnia, the most common sleep disorder, is characterized by persistent difficulty in falling or staying asleep despite adequate opportunity to sleep, leading to daytime fatigue and mental dysfunction. As sleep is a sophisticated physiological process generated by a network of neuronal systems that cannot be reproduced in-vitro, pre-clinical development of hypnotic drugs requires in-vivo investigations. ⋯ Only few valid insomnia models are currently available, although many experimental conditions lead to disturbance of physiological sleep. We categorized these conditions as a function of the procedure used to induce perturbation of sleep, and we discuss their respective advantages and pitfalls with respect to validity, feasibility and translational value to human research.