The Journal of comparative neurology
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Despite the known major role of skin blood vessel innervation in blood flow control, particularly in disease, little information on the co-innervation of blood vessels by sensory and autonomic fibers and the relationships of these fibers to one another is available. To fill this gap, we performed a light and electron microscopic analysis of the innervation of skin vessels by sensory and autonomic fibers by using the rat and monkey lower lips as a model. In rats, double-labeling immunocytochemistry revealed that combinations of fibers immunoreactive for substance P (SP) and dopamine-beta-hydroxylase (DbetaH), SP and vesicular acetylcholine transporter (VAChT), as well as DbetaH and VAChT occurred only around blood vessels in the lower dermis. ⋯ In monkeys, double-labeling immunocytochemistry was performed for SP-DbetaH and SP-VAChT only. The results obtained are similar to those found in rats; however, the fiber density was greater in monkeys. Our findings suggest that the regulation of skin microcirculation might be the result of the coordinated functions of sensory and autonomic fibers.
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The projections from the brainstem to the midline and intralaminar thalamic nuclei were examined in the rat. Stereotaxic injections of the retrograde tracer cholera toxin beta -subunit (CTb) were made in each of the intralaminar nuclei of the dorsal thalamus: the lateral parafascicular, medial parafascicular, central lateral, paracentral, oval paracentral, and central medial nuclei; in the midline thalamic nuclei-the paraventricular, intermediodorsal, mediodorsal, paratenial, rhomboid, reuniens, and submedius nuclei; and, in the anteroventral, parvicellular part of the ventral posterior, and caudal ventral medial nuclei. The retrograde cell body labeling pattern within the brainstem nuclei was then analyzed. ⋯ In addition, most intralaminar injections resulted in retrograde cell body labeling in the substantia nigra, nucleus Darkschewitsch, interstitial nucleus of Cajal, and cuneiform nucleus. Details concerning the pathways from the spinal trigeminal, nucleus tractus solitarius, raphe magnus, raphe pallidus, and the rostral and caudal linear raphe nuclei to subsets of midline and intralaminar thalamic sites are discussed in the text. The discussion focuses on brainstem-thalamic pathways that are likely involved in arousal, somatosensory, and visceral functions.
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The enzyme Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is widely distributed in the nervous system. A previous report describes immunostaining for CaMKII alpha in dorsal root ganglion (DRG) neurons. In this study, CaMKII alpha is colocalized in the rat with three putative markers of nociceptive DRG neurons, isolectin Griffonia simplicifolia (I-B4), identifying small-diameter, "peptide-poor" neurons; calcitonin gene-related peptide (CGRP), identifying " peptide-rich" neurons; or the vanilloid receptor 1 (VR1), identifying neurons activated by heat, acid, and capsaicin. ⋯ The mean diameter of CaMKII alpha - labeled neurons was approximately 27 microm, confirming that this enzyme was preferentially localized in small DRG neurons. The results indicate that subpopulations of DRG neurons containing CaMKII alpha are likely to be involved in the processing of nociceptive information. Thus, this enzyme may play a critical role in the modulation of nociceptor activity and plasticity of primary sensory neurons.
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Neurons from varied regions of the central nervous system can show widely divergent responses to electrical stimuli that are determined by cell-specific differences in ion channel composition. The well-ordered and highly characterized peripheral auditory system allows one to explore the significance of this diversity during the final stages of postnatal development. We examined the electrophysiological features of murine spiral ganglion neurons in vitro at a time when recordings could be made from the cell bodies before myelination. ⋯ Taken together, these results indicate that the distribution of a set of voltage-gated potassium channels may relate specifically to a particular range of coding frequencies. These studies also suggest that intrinsic properties of spiral ganglion neurons can contribute to the characteristic responses of the peripheral auditory system. Their potential role in development and adult function is discussed.
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Distinctive subsets of glutamatergic neurons in cerebral cortex sequester the transition metal zinc within the synaptic vesicles of their axon terminals. In the present study we used histochemical localization of synaptic zinc to investigate normal postnatal development and experience-dependent plasticity of zinc-containing circuits in somatosensory barrel cortex of rats. First, we found that zinc-containing cortical circuits are dynamically reorganized between postnatal day (P) 0 and P28. ⋯ This resulted in more intense zinc staining in deprived barrels compared with adjacent, nondeprived barrels. Notably, the influence of experience on development of zinc circuits was most robust during a critical period extending from about P14, when an effect of whisker trimming first could be observed, through P28, after which time chronic deprivation no longer resulted in heightened levels of synaptic zinc in lamina IV. These findings indicate that sensory input can have a marked influence on development of cortical circuits, including those within lamina IV, throughout the first postnatal month.