The Journal of comparative neurology
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Skin innervation during wound healing was investigated using immunocytochemical staining with the panneuronal marker antiprotein gene product (PGP) 9.5, which labels the entire innervation of the skin throughout development and in the adult. Full-thickness skin wounds in the hairy skin of the foot in neonatal rats result in pronounced hyperinnervation of the tissue that persists long after the wound has healed (at least 12 weeks). Quantification of this hyperinnervation by image analysis indicates that skin innervation density in the wounded area can increase up to 300%. ⋯ Furthermore, pretreatment of neonates with 6-hydroxydopamine, which destroys the sympathetic innervation, does not significantly reduce the overall sprouting response, as identified by anti-PGP9.5 staining. Behavioural sensory testing revealed a 50% drop in the mechanical threshold in the wounded area after 3 weeks. These remarkably long-term and specific effects on sensory terminal axons following neonatal skin wounding indicate the plasticity of cutaneous innervation density following alterations in the target tissue at a critical stage of development.
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A serial pathway from a thalamic nucleus (DLM; the medial portion of the dorsolateral nucleus of the anterior thalamus) to a cortical region (lMAN; the lateral magnocellular nucleus of the anterior neostriatum) to a motor-cortical region (RA; the robust nucleus of the archistriatum) is necessary for vocal production during song learning in juvenile zebra finches but not for the recitation of a song already learned by adults. To obtain new information about the possible function of the DLM-->lMAN-->RA pathway in vocal learning, we used anterograde and retrograde tract-tracing techniques (pressure injections of DiI and DiA) to map the pattern of axonal connections between these brain regions in adult male zebra finches. Results revealed two topographically organized pathways that traverse the songbird forebrain in parallel. ⋯ Konishi, 1991, Soc. Neurosci. Abstr. 18:527) suggests that these pathways might subserve some form of auditory or auditory-motor mapping.
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Chronic constriction injury to the rat's infraorbital nerve (IoN-CCI) induces asymmetric face grooming directed to the injured nerve territory and, beginning at 7-12 days postoperative, hyperresponsiveness to mechanical stimulation in this territory (B. P. Vos, A. ⋯ Neither condition nor stimulus intensity affected fos-LI in the contralateral medullary dorsal horn. Positive correlations were found between the behavioral parameters of increased trigeminal nociceptive activity and the total amount of fos-LI in the ipsilateral medullary dorsal horn. The results demonstrate that IoN-CCI induces significant alterations in the central processing of afferent signals, which may underlie behavioral manifestations of increased nociceptive activity.
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Expression of trk receptors in the developing and adult human central and peripheral nervous system.
A family of tyrosine receptor kinases known collectively as trk receptors plays an essential role in signal transduction mediated by nerve growth factor and related neurotrophins. To localize the major trk receptors (trkA, B and C) in the developing and adult central (CNS) and peripheral (PNS) nervous system, we generated monoclonal antibodies (MAbs) to extracellular (MAbs E7, E13, E16, E21, E29) and intracellular (MAb I2) domains of human trkA fused to glutathione S-transferase. Several MAbs (E7, E13, E16) recognized glycosylated trkA (gp140trk and gp110trk) in Western blots, one MAb (E7) recognized non-glycosylated (p80trk) and glycosylated trkA in immunoprecipitation assays, and two MAbs (E13, E29) detected trkA on the cell surface of NIH3T3 cells transfected with a trkA cDNA. ⋯ Although the distribution and intensity of trk immunoreactivity changed with the progressive maturation of the CNS and PNS, immunoreactive trk receptors were detected in neurons of the adult human hippocampus, nucleus basalis of Meynert, cerebellum, spinal cord, and DRG. This first study of trk receptor proteins in the developing and adult human CNS and PNS documents the expression of these receptors in subsets of neurons throughout the developing and adult nervous system. Thus, although the expression of trk receptor proteins is developmentally regulated, the constitutive expression of these neurotrophin receptors by neurons in many regions of the adult human CNS and PNS implies that mature trk receptor-bearing neurons retain the ability to respond to neurotrophins long after terminal neuronal differentiation is complete.
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The postsynaptic effects of dopamine in the striatum are mediated mainly by receptors encoded by D1, D2, and D3 dopamine receptor genes. The D1 and D2 genes are the most widely expressed in the caudate-putamen, the accumbens nucleus, and the olfactory tubercle. Several anatomical studies, including studies using in situ hybridization with oligonucleotide and cDNA probes, have suggested that D1 and D2 receptors are segregated into distinct efferent neuronal populations of the striatum: D1 in substance P striatonigral neurons and D2 in enkephalin striatopallidal neurons. ⋯ The present results demonstrate that the D1 and D2 receptor mRNAs are segregated, respectively, in substance P and enkephalin neurons in the caudate-putamen and accumbens nucleus (shell and core) and in the olfactory tubercle (for their largest part). A very small percentage of neurons may coexpress both genes. These results confirm that the D1 and D2 receptor genes are expressed in distinct populations of striatal efferent neurons in the normal adult rat.