Neuroscience letters
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Neuroscience letters · Feb 1999
Spinal integration of antidromic mediated cutaneous vasodilation during dorsal spinal cord stimulation in the rat.
The purpose of this study was to determine the involvement of supraspinal centers and spinal synaptic integration in cutaneous vasodilation mediated by dorsal spinal cord stimulation (DCS). Laser Doppler flowmetry was used to assess cutaneous blood flow changes in the rat hindpaw during DCS with a unipolar ball electrode placed at the L2-L3 spinal level. ⋯ Inhibition of synaptic activity with topical application of muscimol (0.2 mM) on the dorsal surface of the spinal cord markedly attenuated the DCS response. In conclusion DCS-induced vasodilation involved synaptic integration but did not require input from rostral spinal sites or supraspinal areas.
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Neuroscience letters · Jan 1999
Cutaneous afferents producing a reflex pupil dilation in anesthetized rats.
Cutaneous afferents producing a reflex pupil dilation were examined using natural mechanical stimulation of the hindlimb skin and electrical stimulation of a sural nerve in anesthetized, artificially ventilated rats. Pupil diameter was continuously recorded after magnification using a microscope connected to a charge coupled device camera. Innocuous brushing, or weak pressing of the skin, did not have any effect on pupil diameter, while pressing the skin more than 720 g/cm2 produced a pressure-dependent pupil dilation. ⋯ Electrical stimulation of a sural afferent nerve with weak intensity, which was supra-threshold for Abeta-afferents and sub-threshold for Asigma-afferents, induced a reflex pupil dilation. This dilation continued to increase with further increases in stimulus intensity which involved excitation of Asigma afferents and C afferents. It is concluded that Abeta, Asigma and C afferents in the skin can work as afferents in eliciting reflex pupil dilation in anesthetized rats.
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Neuroscience letters · Nov 1998
Prediction of migraine attacks using a slow cortical potential, the contingent negative variation.
Amplitudes of contingent negative variation (CNV) as a slow cortical potential in migraine patients were recorded before and after migraine attacks. The level of CNV amplitudes, especially of the early component, showed a trend in rise of negativity 1 day before the attack, whereas amplitudes were normal for 2-3 days following an attack. In most cases the attack occurred when the CNV amplitude showed maximum negativity. We conclude that migraine-susceptible days are indicated by a high CNV amplitude the day before the attack.
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Neuroscience letters · Oct 1998
Nerve growth factor evokes hyperalgesia in mice lacking the low-affinity neurotrophin receptor p75.
Endogenous nerve growth factor (NGF) has been shown to be an important mediator of inflammatory pain and exogenous application of recombinant human NGF (rhNGF) produces pain and hyperalgesia in animals and humans. Since NGF can act through two receptors types, the high affinity tyrosine kinase A (trkA) receptor and the low affinity p75 receptor, we used transgenic mice lacking p75 to analyse the relative importance of these receptors. ⋯ Although animals lacking p75 have increased mechanical and thermal withdrawal thresholds they developed both heat and mechanical hyperalgesia after systemic injection of rhNGF whose magnitude did not differ significantly from wildtype animals. This means that NGF-induced hyperalgesia can occur in the absence of the p75 receptor and suggests that the trkA receptor is sufficient to mediate the acute noxious action of NGF.
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Neuroscience letters · Oct 1998
Increased ciliary neurotrophic factor expression in reactive astrocytes following spinal cord injury in the rat.
Expression of ciliary neurotrophic factor (CNTF) was observed in reactive astrocytes in injured spinal cord of the adult rat. After unilateral incision of the dorsal funiculus at a midthoracic level, the rats were sacrificed on the day of postoperation (DPO) 3, 7, 14 or 28. ⋯ Double immunofluorescence histochemistry revealed that all CNTF-like immunoreactive cells showed GFAP-like immunoreactivity. The CNTF upregulation in the reactive astrocytes may play important roles in repair process after spinal cord injury.