The European journal of neuroscience
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A double-labelling procedure combining immunohistochemical staining with in situ hybridization using a radiolabelled cRNA probe was employed to demonstrate oestrogen receptor-like immunoreactivity and preproenkephalin-A mRNA in the medullary and spinal dorsal horn of female rats. Both markers labelled large numbers of neurons in the substantia gelatinosa and its trigeminal homologue. ⋯ Previous studies have shown that oestrogen receptors can bind to the promoter region of the preproenkephalin-A gene, and studies on the hypothalamus have demonstrated that oestrogen regulates enkephalin expression in select neuronal populations. The present results demonstrate that enkephalinergic neurons in the superficial dorsal horn contain oestrogen receptors and suggest that oestrogen may play an important role in the modulation of sensory and nociceptive processing in the lower medulla and spinal cord.
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Comparative Study
Leukaemia inhibitory factor induced in the sciatic nerve after axotomy is involved in the induction of galanin in sensory neurons.
Dramatic changes occur in neuropeptide expression in sensory and sympathetic neurons following axonal injury. Based on the finding that the cytokine leukemia inhibitory factor (LIF) plays an important role in mediating these changes in sympathetic neurons, its participation in triggering changes in sensory neurons was examined. By the use of transgenic mice in which the LIF gene had been knocked out, LIF was found to contribute to the induction of galanin expression in dorsal root ganglia (DRG) after sciatic nerve lesion. ⋯ DRG were capable of making substantial amounts of LIF mRNA when placed in explant cultures, but, in vivo, only a slight induction was found even when both central and peripheral nerve processes of these sensory neurons were transected. These latter observations suggest that, in contrast to the superior cervical ganglia, the DRG environment inhibits the lesion-induced expression of LIF in vivo and/or explanted DRG produce stimulatory signals not found in vivo. Together with the data on the induction of galanin, these observations provide evidence that LIF, generated at a site at some distance from the ganglion, is involved in triggering part of the cell body reaction in sensory neurons.
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Comparative Study Clinical Trial
Pain processing in four regions of human cingulate cortex localized with co-registered PET and MR imaging.
Neurosurgical and positron emission tomography (PET) human studies and animal electrophysiological studies show that part of the anterior cingulate cortex (ACC) is nociceptive. Since the contribution of the ACC to pain processing is poorly understood, this study employed PET and magnetic resonance (MR) image co-registration in grouped and individual cases to locate regions of altered relative regional cerebral blood flow (rCBF). Seven right-handed, neurologically intact males were subjects; each received neuropsychological and pain threshold testing. ⋯ The rostral site of elevated rCBF in the group was at the border of areas 24/24' and areas 32/32' although most cases had a site of elevation more rostral in the perigenual cingulate cortex. The ACC site of reduced rCBF was in areas 8 and 32 and that in the PCC included much of areas 29/30 in the callosal sulcus, areas 23b and 31 on the cingulate gyral surface and parietal area 7m. The localization of relative rCBF changes suggests different roles for the cingulate cortex in pain processing: (i) elevated rCBF in area 24' may be involved in response selection like nocifensive reflex inhibition; (ii) activation of the perigenual cortex may participate in affective responses to noxious stimuli like suffering associated with pain; and (iii) reduced rCBF in areas 8 and 32 may enhance pain perception in the perigenual cortex, while that in the PCC may disengage visually guided processes.
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In the adult barrel cortex of the rat the calcium-binding proteins calbindin D28k (CALB) and parvalbumin (PARV) are found in separate populations of GABAergic nonpyramidal neurons. In layers II to IV of the barrel cortex most PARV-immunoreactive neurons are likely to derive from a subpopulation of CALB-immunoreactive neurons whose CALB immunoreactivity ceases when they begin to express PARV between the second and third postnatal weeks. The aim of this study was to investigate the influence of subcortical afferents on the neurochemical differentiation of cortical PARV- and CALB-immunoreactive nonpyramidal neurons during development of the barrel cortex. ⋯ In contrast, lesions affecting the globus pallidus, zona incerta and reticular thalamic nucleus transiently increased the number of PARV-immunoreactive neurons in layers II and III, but had no effect on the number of CALB-positive cells. From 3 weeks onwards no differences were found between control and lesioned hemispheres after injections into either the ventroposterior thalamic nuclei or the magnocellular basal forebrain. These results suggest that CALB and PARV expression in nonpyramidal cortical neurons can be reversibly modulated in opposite directions by different cortical afferents during postnatal development.
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The cerebellar and vestibular nuclei consist of a heterogeneous group of inhibitory and excitatory neurons. A major proportion of the inhibitory neurons provides a GABAergic feedback to the inferior olive, while the excitatory neurons exert more direct effects on motor control via non-olivary structures. At present is is not clear whether Purkinje cells innervate all types of neurons in the cerebellar and vestibular nuclei or whether an individual Purkinje cell axon can innervate different types of neurons. ⋯ Glycine-containing terminals were relatively scarce ( < 2% of the GABA-containing terminals) and frequently contacted the larger non-GABAergic, non-glycinergic neurons. To summarize, Purkinje cell axons evoke their effects through different types of neurons present in the cerebellar and vestibular nuclear complex. The observation that individual Purkinje cells can innervate both excitatory and inhibitory neurons suggests that the excitatory cerebellar output system and the inhibitory feedback to the inferior olive are controlled simultaneously.