Neuroscience letters
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Neuroscience letters · Jul 2000
gamma-aminobutyric acid- and glycine-immunoreactive neurons postsynaptic to substance P-immunoreactive axon terminals in the superficial layers of the rat medullary dorsal horn.
gamma-Aminobutyric acid (GABA)ergic and glycinergic neurons were examined light- and electron-microscopically in laminae I and II of the medullary dorsal horn (MDH, i.e. spinal trigeminal nucleus caudalis in the rat). The majority of GABA- and glycine (Gly)-immunoreactive (-ir) neurons showed both GABA- and Gly-immunoreactivities (-IRs). ⋯ GABA- and Gly-ir neuronal profiles were postsynaptic to substance P-ir axon terminals. These results suggest that nociceptive information being carried by primary afferent SP-fibers may be relayed directly to GABAergic and glycinergic neurons in laminae I and II of the MDH.
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Neuroscience letters · Jul 2000
Noxious hot and cold stimulation produce common patterns of brain activation in humans: a functional magnetic resonance imaging study.
We used functional magnetic resonance imaging (fMRI) to determine whether similar brain regions activate during noxious hot and cold stimulation. Six male subjects underwent whole brain fMRI during phasic delivery of noxious hot (46 degrees C) and noxious cold (5 degrees C) stimulation to the dorsum of the left hand. Mid-brain regions activated included thalamus, basal ganglia and insula. ⋯ Most regions activated bilaterally but with stronger activation contralateral to the stimulus. Noxious cold stimulation produced significantly increased volumes of activation compared to noxious heat in prefrontal areas only. Our results suggest a similar network of regions activate common to the perception of pain produced by either noxious hot or cold stimulation.
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Neuroscience letters · Jul 2000
Role of signals from the dorsal root ganglion in neuropathic pain in a rat model.
We examined whether signals from the neuroma or the dorsal root ganglion of the injured segment are critical for the generation of neuropathic pain. To this aim, we used a rat model of peripheral neuropathy made by transecting the inferior and superior caudal trunks at the level between the S1 and S2 spinal nerves under enflurane anesthesia. These animals displayed tail-withdrawal responses to normally innocuous mechanical stimulation applied to the tail with a von Frey hair (2 g). ⋯ Transection of the S1 spinal nerve between the dorsal root ganglion and neuroma did not change the behavioral signs of neuropathic pain. In contrast, S1 dorsal rhizotomy significantly reduced the behavioral signs. The data suggest that signals arising from the dorsal root ganglion cells of the injured segment, but not from the neuroma, are critical for the generation of neuropathic pain in this model.