The Journal of neuroscience : the official journal of the Society for Neuroscience
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The use of human Schwann cells (SCs) in transplantation to promote regeneration in central and peripheral neural tissues must be preceded by efforts to define the factors that regulate their functional expression. Adult-derived human SCs can be isolated and purified in culture, but the culture conditions that allow their full differentiation have not yet been defined. We tested the functional capacity of these cells to enhance axonal regeneration and myelinate regenerating axons in vivo by transplanting them into the damaged PNS of an immune-deficient rat. ⋯ The number of myelinated axons and the cross-sectional area of the cable were significantly greater in channels seeded with human SCs when compared to channels containing the diluted Matrigel solution alone. We conclude that purified cultured human SCs can survive and substantially enhance axonal regeneration when transplanted into the injured PNS of an immune-deficient rat. Some of the transplanted human SCs are capable of myelinating regenerating rat axons but are less successful than the host SCs.
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The mammalian acoustic startle response (ASR) is a relatively simple motor response that can be elicited by sudden and loud acoustic stimuli. The ASR shows several forms of plasticity, such as habituation, sensitization, and prepulse inhibition, thereby making it an interesting model for studying the underlying neuronal mechanisms. Among the neurons that compose the elementary startle circuit are giant neurons in the caudal pontine reticular nucleus (PnC), which may be good candidates for analyzing the neuronal basis of mammalian behavior. ⋯ Axon collaterals and terminal arbors were found in the reticular formation as well as in cranial and spinal motoneuron pools. The results of this study indicate that giant PnC neurons form a sensorimotor interface between the cochlear nuclear complex and cranial and spinal motoneurons. This neuronal pathway implies that the elementary acoustic startle circuit is composed of only three central relay stations and thus appears to be organized more simply than assumed in the past.
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Substance P (SP) and other related tachykinins such as neurokinin B (NKB) have been studied widely as mediators of sensory information. The release of SP into the dorsal horn of the spinal cord is increased during nociception, and SP activates nociception-specific dorsal horn neurons. The tachykinin NKB has antinociceptive effects in the spinal cord and is contained in intrinsic spinal neurons; thus, NKB may also contribute to the processing of sensory information. ⋯ Peptide and receptor mRNA expression levels were normalized to beta-actin mRNA levels, which did not change during the treatments. Formalin (2 or 6 hr) or CFA (4 d) injection produced approximately a twofold increase in SP-encoding PPT mRNA expression in the ipsilateral lumbar DRG. Increased activity in primary afferent neurons containing SP may stimulate the production of SP precursors, providing substrate for increased SP production, release, and turnover in the dorsal horn and periphery.(ABSTRACT TRUNCATED AT 250 WORDS)
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The basal ganglia receive massive inputs from the neocortex and send outputs that exert both inhibitory and disinhibitory control over parts of the frontal cortex and brainstem. Between these basal ganglia inputs and outputs lies the striatum, which receives most of the cortical afferents and projects to the basal ganglia output nuclei--the globus pallidus and substantia nigra. To analyze this system we conjointly labeled, in squirrel monkeys, sensorimotor cortical inputs to the striatum and striatal outputs to the globus pallidus. ⋯ One function of striatal modularity may thus be to set up an associative network in the striatum, which might contribute to sensorimotor learning. We also found that some sets of matrisomes did not receive strong sensorimotor inputs, even though they projected to regions of GPe and GPi that are near the sensorimotor-recipient zones described above. Thus, the matrisomal system may sort MI/SI inputs and other inputs before transfer to paired regions of GPe and GPi.
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Potential cellular substrates for functions ascribed to the dopamine D2 receptor were examined in rat brain using immunoperoxidase for localization of a D2 receptor peptide and immunogold staining for the catecholamine biosynthetic enzyme tyrosine hydroxylase (TH). Specificity of the rat polyclonal antiserum, raised against a 15 amino acid fragment from the third intracellular loop of the D2 receptor, was shown by immunoblot analysis and by selective labeling of cultured Chinese hamster ovary cells permanently transfected with the cDNA for the D2 receptor. Although the light microscopic distribution of immunolabeling for the D2 peptide was diffuse, it was selectively localized to regions containing dopamine cells (substantia nigra and ventral tegmental area) or their forebrain projections (dorsal and ventral striatum, nucleus accumbens, and olfactory tubercles). ⋯ In dually labeled sections, most D2 peptide-immunoreactive terminals lacked detectable immunolabeling for TH. However, in fortunate planes of section, peroxidase product for D2 peptide immunoreactivity was occasionally seen in pre-terminal portions of axons whose terminal varicosities contained immunogold labeling for TH. These ultrastructural results are consistent with the localization of a dopamine D2 receptor-like protein that is strategically positioned to subserve (1) autoreceptor functions at the level of dendrites in the midbrain and presynaptic axon terminals in the striatum, as well as (2) postsynaptic actions on striatal spiny dendrites and other nondopamine terminals.