Brain research bulletin
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Brain research bulletin · May 2002
Cutaneous vascular responses evoked by noxious stimulation in rats with the spinal nerve ligation-induced model of neuropathy.
Antidromic activation of nociceptive nerve fibres innervating the skin produces an axon reflex that involves extravasation and vasodilation of cutaneous blood vessels. We determined whether the axon reflex of the hindlimb skin is influenced by an experimental model of neuropathy induced by unilateral ligation of spinal nerves L(5) and L(6) in the rat. Ligation of spinal nerves induced symptoms mimicking tactile allodynia, as indicated by a marked decrease of the hindlimb withdrawal threshold to mechanical stimulation. ⋯ The results indicate that ligation of spinal nerves induces an attenuation of the axon reflex. This attenuation reflects a decrease in the efferent function of primary afferent nociceptors innervating the hypersensitive skin of the hindpaw. The attenuation of antidromically-induced vascular responses was not caused by overriding sympathetic activity, as indicated by lack of blood flow effects by lidocaine blocks or a transection of the sciatic nerve.
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Brain research bulletin · May 2002
Monoamine metabolism and sympathetic nervous activation following subarachnoid haemorrhage: influence of gender and hydrocephalus.
Subarachnoid haemorrhage is a serious condition, often accompanied by cerebral vasospasm and hydrocephalus, which may result in delayed cerebral ischaemia and neurological deterioration. While the mechanisms responsible remain unknown, activation of the sympathetic nervous system, leading to elevated levels of circulating catecholamines is, at least in part, implicated. In this study, we sought to examine the importance of sympathetic nervous activation and its relation to brain monoaminergic neurotransmission in 25 patients following subarachnoid haemorrhage by examining plasma and cerebrospinal fluid levels of the catecholamines noradrenaline, adrenaline and dopamine, and their metabolites. ⋯ Lower cerebral perfusion pressures were observed in those patients in whom cerebrospinal fluid concentrations of noradrenaline and dopamine metabolites were high. A marked sympathetic nervous activation, more pronounced in women and in those with hydrocephalus, occurs following subarachnoid haemorrhage. The diminished cerebral perfusion seen following subarachnoid bleeding may occur as a result of activation of central catecholaminergic neurones.
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Brain research bulletin · Apr 2002
ReviewNeurotrophic factors, gene therapy, and neural stem cells for spinal cord repair.
Several experimental strategies have been employed to minimize tissue damage and to enhance axonal growth and regeneration after spinal cord injury. The transplantation of suitable cell types to provide an axonal growth substrate and the application of growth factors have been shown to augment morphological and sometimes functional recovery. In this review we discuss the use of neural stem cell transplants and neurotrophic factor delivery by gene therapy to improve axonal regeneration in animal models of spinal cord injury.
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Brain research bulletin · Mar 2002
NMDA and AMPA/kainate glutamatergic agonists increase the extracellular concentrations of GABA in the prefrontal cortex of the freely moving rat: modulation by endogenous dopamine.
Using microdialysis in the prefrontal cortex, this study investigated first the effects of the ionotropic glutamatergic agonists NMDA and AMPA on extracellular concentrations of GABA, and second, the modulation of these effects by increasing endogenous dopamine. NMDA (20, 100, and 500 microM) and AMPA (1, 20, and 100 microM), perfused through the microdialysis probe for 60 min, produced a dose-related increase of extracellular concentrations of GABA in the prefrontal cortex of the awake rat. NMDA 100 and 500 microM produced a maximal increase of extracellular GABA of 150 +/- 38% and 245 +/- 75% of baseline, respectively. ⋯ However, increases of endogenous dopamine at 0.5-0.7 nM did potentiate the increases of extracellular GABA produced by AMPA (20 microM) (from 140% to 240% of baseline), but not by NMDA (100 microM), in this area of the brain. These effects were attenuated by the perfusion of (-)sulpiride (D2 antagonist), but not by the perfusion of SCH-23390 (D1 antagonist). These results suggest that glutamate, through the activation of both NMDA and AMPA/kainate ionotropic receptors, facilitates GABAergic transmission in the prefrontal cortex, and that dopamine can modulate the effects of glutamate through AMPA/kainate receptors on GABA transmission in this area of the brain.
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Brain research bulletin · Mar 2002
Dynamic changes and spatial correlation of EEG activities during cold pressor test in man.
To explore the effects of tonic cold pain in man, the pain rating (intensity and distress), skin temperature, and continuous EEG recording were conducted before, during, and after cold pressor test (CPT) in 15 young healthy males. The acquired electroencephalogram (EEG) data was analysed in four ways: (1) comparison of EEG topographic patterns and power spectra across baseline, CPT, and post-CPT; (2) dynamic EEG changes during CPT; (3) correlation of EEG activities at the isolated focal maxima across the three experimental stages; and (4) spatial correlation of EEG powers among the focal sites during CPT. ⋯ This new evidence and the detailed EEG effects in CPT may enhance our understanding of the dynamics in cerebral processing of tonic noxious information. Alpha reduction may reflect the attention processing in nociceptive input, and the delta/theta/beta activation may be related to the motivational modulation of the brain.