The Journal of comparative neurology
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The extent of the sprouting of sympathetic postganglionic fibers in the dorsal root ganglion (DRG) and the peripheral nerves was examined in neuropathic rats at different postoperative times. After the L5 and L6 spinal nerves were ligated on one side, three different pain behavior tests (representing mechanical allodynia, cold allodynia, ongoing pain exacerbated by cold stress) were performed at various time intervals. The sympathetic postganglionic fibers were visualized by immunostaining with antibodies to tyrosine hydroxylase (TH). ⋯ The numerical density of sympathetic fibers in the DRG of an injured segment was significantly higher at 1, 4, and 20 weeks after neuropathic surgery as compared to the normal, suggesting that there is sprouting of sympathetic fibers in the DRG after peripheral nerve injury. Sprouting of sympathetic fibers in the DRG was extensive as early as 2 days after the spinal nerve ligation, and the sprouted fibers were almost completely eliminated after sympathectomy. The data suggest that sympathetic innervation of the DRG may play an important role in the development and maintenance of sympathetically maintained neuropathic pain.
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We present a detailed description of the somatodendritic and axonal features of the Golgi-impregnated Lugaro cell in the rat cerebellar cortex. This neuron, present throughout the cerebellum, is characterized by a fusiform cell body located at the border between the granular and Purkinje cell layers, horizontal bipolar dendrites extending in the parasagittal plane and an axon projecting exclusively to the molecular and granular layers. A quantitative analysis of 77 Lugaro cells confirms the somatodendritic homogeneity of this cell type. ⋯ In a few samples, one or two remote axon collaterals were seen to extend longitudinally in the lower molecular layer for a few hundred microns, in the same direction as the parallel fibers. In all cases a few collaterals projected into the granular layer. In view of its dense afferentation by Purkinje cell recurrent collaterals and its profuse inhibitory projection in the molecular layer, the Lugaro cell could act as a feedback interneuron on the corticocerebellar output.
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The macula lagenae, an otolithic hair-cell organ with probable vestibular function, lies close to the apical end of the avian auditory hair-cell epithelium, the papilla basilaris. In an earlier study in the pigeon in which lesioning techniques were used, Boord and Rasmussen ([1963] J. Comp. ⋯ Our results thus imply that there is no processing of information from the macula lagenae in the cochlear nucleus of the chicken. In addition, we studied the origin of the few labeled efferent neurons in the brainstem. The location of all somata encountered was restricted to an area medial to the nucleus facialis dorsalis and corresponded to the dorsal efferent cell group, from which efferents to other vestibular organs also originate.
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The response to injury of ascending collaterals of dorsal root axons within the dorsal column (DC) was studied after neonatal spinal overhemisection (OH) made at different levels of the spinal cord. The transganglionic tracer, cholera toxin conjugated to horseradish peroxidase, and the anterograde tracer, biotinylated dextran amine, were used to label dorsal root ganglion cells with peripheral axons contributing to the sciatic nerve. There was no indication of a regenerative attempt by DC axons at acute survival times (3 days and later) after cervical injury, replicating previous work done at chronic survival periods (Lahr and Stelzner [1990] J. ⋯ Although fetal tissue did not appear to rescue a significant number of DRG neurons, the quantitative analysis showed an enlargement of the largest class of DRG neuron, the class that contributes to the DC projection, in all groups receiving fetal tissue implants. This apparent trophic effect did not affect DC regeneration or neuronal survival after peripheral axotomy. Further studies are needed to determine why DC axons do not regenerate in a neonatal spinal environment or within fetal tissue implants, especially because previous work by others in both the developing and adult spinal cord shows that dorsal root axons will grow within the same type of fetal spinal implant.
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The anatomy and physiological properties of eight non-giant projection interneurones which originate from the locust terminal abdominal ganglion and receive wind and tactile inputs from ovipositor hair receptors are described. Their cell bodies (diameter 25-40 mu m) are clustered in the anterolateral region of the eighth abdominal neuromere, and their axons ascend through either the contralateral or the ipsilateral connective to more anterior abdominal ganglia. In contrast to the giant interneurones, they have small-diameter axons and are not sensitive to cercal hair wind inputs. ⋯ ALIN1-ALIN7 are depolarised and spike in response to wind and direct mechanical deflection of trichoid sensilla on both left and right ovipositor valves. They respond with more spikes to stimulation of hairs on the ventral valve ipsilateral to their main dendritic field. ALIN8, in contrast, shows a delayed inhibitory/excitatory response.