Morphology of geniculo-striate afferents in a prosimian primate

In order to analyze the arborization pattern of single axons innervating layer IV of striate cortex in Galago (a prosimian primate), injections of horseradish peroxidase were made into the white matter below visual cortex. Two distinct fiber types were identified which ramify within different subdivisions of layer IV. Fibers with large axons (type I) have relatively wide terminal arbors which ramify in layer IVa and lower layer III, while those with small axons (type II) arborize in restricted zones of layer IVb. Evidence from previous investigations suggests that terminals of these two fiber types represent the axon terminals of X-like and Y-like geniculate relay cells.     

Cyclic AMP reduction of frequency following ability in peripheral axons

Radioimmunoassays for cAMP demonstrated that a beta-adrenergic agonist, isoproterenol, increased cAMP levels in isolated frog sciatic nerve. Dibutyryl cAMP (db-cAMP) and isoproterenol reduced the amplitude of the compound action potential and decreased the ability of the Xenopus sciatic nerve to follow high frequency stimulation. Similar effects of db-cAMP and a phosphodiesterase inhibitor were seen on intracellularly recorded action potentials of single lobster peripheral axons. These results suggest that cAMP can modulate the electrophysiological response properties of both myelinated and unmyelinated axons.     

Mechanisms of regrowth in the bulbospinal serotonin system following 5,6-dihydroxytryptamine induced axotomy. II. Fluorescence histochemical observations

The degenerative and regenerative processes following 75 μg 5,6-dihydroxytryptamine (5,6-DHT) have been investigated in the bulbospinal serotoninergic system with a fluorescence histochemical technique. Acutely, 1–3 weeks after 5,6-DHT an extensive disappearance of serotoninergic terminals was observed in the spinal gray, inferior olive, and the facial and hypoglossal nuclei, while the spinal trigeminal nucleus and regions of the reticular formation were partially denervated. Concomitantly, large numbers of swollen, highly fluorescent profiles, interpreted as the proximal stumps of lesioned serotoninergic axons, appeared in the medulla oblongata and most rostral cervical spinal cord. The first signs of regenerative sprouting from the swollen proximal stumps appeared one week after 5,6-DHT, and was prominent during subsequent weeks. The rate of reinnervation of different target areas was dependent on the distance to the regrowing axons; it was most rapid in brain stem nuclei. About one month after 5,6-DHT a terminal plexus of normal density had reappeared in both inferior olive and the facial nucleus. The axonal proliferation continued, however, to produce increasingly abnormal hyperinnervations. Certain abnormalities in terminal fiber morphology occurred: the fibers were coarser and exhibited higher fluorescence than normal, and in the facial and motor trigeminal nuclei rather thick, smooth fibers with pericellular arrangement appeared after long survival times (7–19 months). The reinnervation of spinal cord followed a slower time course. A normal amount of innervation was only reformed in the rostral 3–4 mm of the cervical spinal cord, while thoracic and lumbar levels only recovered a small part of the original terminal density.The regenerative growth demonstrated a high degree of specificity, which indicates precise mechanisms of guidance and recognition. These are presumably similar, or identical, to those regulating ontogenetic development of the serotoninergic system. Limitations of these regulatory mechanisms were, however, demonstrated both by the abnormal proximo-distal distribution of regenerated terminals, and in the inferior olivary complex, where the regrowing fibers invaded areas normally devoid of serotoninergic innervation. It is suggested that the drive of axonal growth is derived from an inherent program of the serotoninergic neurons to establish a predetermined amount of axonal arborizations. The role of the target tissue may be a mere provision of cues for recognition. The regulatory neuronal program seems to lack a mechanism to terminate further proliferation when an innervation of normal density has been reformed.     

CSF Monoamine Metabolism in Patients with Tardive Dyskinesia: Effect of Oxypertine and Hydroxyzine Pamoate

Abstract: Cerebrospinal fluid (CSF) HVA, MHPG, 5-HIAA, cAMP and cGMP concentrations were measured in schizophrenic patients with tardive dyskinesia before and after a three-week administration of oxypertine (n = 4), hydroxyzine pamoate (n = 4) or placebo (n = 4). The oxypertine administration resulted in a reduction of the CSF HVA concentration and an elevation of the MHPG and cAMP concentrations, associated with a clinical improvement in tardive dyskinesia. The hydroxyzine administration reduced the CSF 5-HIAA concentration in all the patients and the CSF HVA concentration in two of four patients with a clinical improvement. A reduction in the CSF HVA concentration associated with possible therapeutic effects of oxypertine or hydroxyzine may suggest the normalization of a hyperdopaminergic state. Discussions were held that functional disorders of not only the dopaminergic system but the norepinephrinergic and serotoninergic systems may relate to the pathogenesis of tardive dyskinesia.     

Morphology of jaw-muscle spindle afferents in the rat

The morphology of jaw-muscle spindle afferents in the rat has been studied by intra-axonal injection of horseradish peroxidase. All stained axons were located in the motor root of the trigeminal nerve and could be traced dorsomedially to the vicinity of the trigeminal motor nucleus, where they divided into an ascending branch in the tract of the mesencephalic nucleus and a descending branch in the tract of Probst. Axon collaterals and swellings on fine collateral branches presumed to be synaptic boutons were located in the following regions: the trigeminal motor nucleus, the region dorsal to the trigeminal motor nucleus including the supratrigeminal nucleus, the parvicellular reticular formation immediately caudal to the trigeminal motor nucleus, the reticular formation at the level of the facial nucleus, and the caudal portion of the mesencephalic nucleus. No evidence of a projection to the cerebellum was observed. Boutons were most numerous in the region surrounding the trigeminal motor nucleus, especially dorsally. Here they were not demonstrated in close proximity to counterstained cells, and therefore it was not possible to determine how many of these contacts are located on cells in this region and how many are on the distal dendrites of trigeminal motorneurons. Boutons located within the trigeminal motor nucleus were always confined to a small portion of the nucleus and were significantly larger than those located dorsally. Some boutons were found in close apposition to trigeminal motorneurons and presumably make somatic contacts. These results suggest that jaw-muscle spindle afferents make somatic and proximal dendritic contacts with only a limited number of trigeminal motorneurons and also project to masticatory interneuronal regions dorsal and caudal to the motor nucleus.     

The postnatal development of the optic nerve of a reptile (Vipera aspis): A quantitative ultrastructural study

The number of axons in the optic nerve of the ovoviviparous reptile Vipera aspis was estimated from electron micrographs taken during the first 5 weeks of postnatal life. One to two days after birth, the optic nerve contains about 170,000 fibres, of which about 9% are myelinated. At the end of the fifth postnatal week, the number of optic fibres has fallen to about 100,000, of which about 42% are myelinated. This fibre loss continues after the fifth postnatal week, since in the adult viper the nerve contains about 60,000 fibres, of which 85% are myelinated; overall, about 65% of the optic nerve fibres present at birth disappear before the number of axons stabilises at the adult level. This study shows, for the first time, that the mode of development of the visual axons of reptiles is not that of anamniote vertebrates but similar to that of birds and mammals.     

Involvement of 5-HT(2) serotonergic receptors of the nucleus raphe magnus and nucleus reticularis gigantocellularis/paragigantocellularis complex neural networks in the antinociceptive phenomenon that follows the post-ictal immobility syndrome

The post-ictal immobility syndrome is followed by a significant increase in the nociceptive thresholds in animals and men. In this interesting post-ictal behavioral response, endogenous opioid peptides-mediated mechanisms, as well as cholinergic-mediated antinociceptive processes, have been suggested. However, considering that many serotonergic descending pathways have been implicated in antinociceptive reactions, the aim of the present work is to investigate the involvement of 5-HT(2)-serotonergic receptor subfamily in the post-ictal antinociception. The analgesia was measured by the tail-flick test in seven or eight Wistar rats per group. Convulsions were followed by statistically significant increase in the tail-flick latencies (TFL), at least for 120 min of the post-ictal period. Male Wistar rats were submitted to stereotaxic surgery for introduction of a guide-cannula in the rhombencephalon, aiming either the nucleus raphe magnus (NRM) or the gigantocellularis complex. In independent groups of animals, these nuclei were neurochemically lesioned with a unilateral microinjection of ibotenic acid (1.0 microg/0.2 microL). The neuronal damage of either the NRM or nucleus reticularis gigantocellularis/paragigantocellularis complex decreased the post-ictal analgesia. Also, in other independent groups, central administration of ritanserin (5.0 microg/0.2 microL) or physiological saline into each of the reticular formation nuclei studied caused a statistically significant decrease in the TFL of seizing animals, as compared to controls, in all post-ictal periods studied. These results indicate that serotonin input-connected neurons of the pontine and medullarly reticular nuclei may be involved in the post-ictal analgesia.     

Syncytial coupling of neurons in tissue culture and early ontogenesis

Computerized time-lapse video recording was used to detect the process of formation of syncytial couplings between the processes of different neurons in dissociated neuron cultures. These studies showed that once the processes of one neuron had formed connections with another neuron, death of the cell body (its trophic center) was not followed by Wallerian degeneration. Translocation of cytoplasmic varicosities along the branches of one neuron to another was observed over periods of several hours. Electron microscopic studies of the nerve processes of cells in the intramural intestinal plexus in the early postnatal period demonstrated all the transitional states from fusion and perforation of the membranes of contacting dendrites to complete fusion of the neuroplasm of processes with formation of residual membranous structures at the location of the former intercellular contact. __________ Translated from Morfologiya, Vol. 131, No. 2, pp. 7–15, March–April, 2007.     

Dicer is essential for neuronal polarity

Dicer, an RNase III endonuclease, is the enzyme which cleaves microRNA (miRNA) and small interfering RNA (siRNA) precursors into 21–25 nucleotide species. This cleavage is an essential step in the biogenesis of these small noncoding RNA molecules. In their mature forms, siRNA and miRNAs function to regulate gene expression through different mechanisms (Bartel, 2004). To investigate the role of Dicer and microRNAs in neuronal polarity development, we used mice in which the RNase III domain of Dicer was conditionally floxed. To knockout Dicer gene, hippocampal neurons were electroporated with Cre together with pmaxGFP^® plasmid by Amaxa^® Mouse Neuron Nucleofector^® Kit. Neuronal polarity was analyzed at 3 days in vitro (DIV). Neurons expressing pmaxGFP^® showed normal polarity. In contrast, the majority of neurons transfected with Cre developed multiple axons. We found multiple axons were significantly increasing. Here we explore Dicer function in neuronal polarity by inactivating it in the hippocampal neuron using the Cre/loxP approach. Neurons which lack Dicer have multiple axons, demonstrating that Dicer is essential for neuron polarity, providing evidence that Dicer function is required to neuronal development.     

人胚胎嗅鞘细胞植入鼠半横断脊髓的初步观察(英文)

目的观察人胚胎嗅鞘细胞(olfactoryensheathingcells,OECs)移植对成鼠脊髓轴突再生的影响。方法将分离、纯化、培养2周的人胚胎OECs,移植于10只成年SD大鼠半横断胸髓(T10)的两端;对照组10只同样方法给予等量的DMEM培养液。6周后组织切片,行HE染色、嗜银染色以及髓鞘碱性蛋白(MBP)和抗神经生长因子受体抗体(NGFR)免疫组化检查。结果OECs移植组6周后脊髓大体标本显示初步愈合现象;组织学观察,OECs呈NGFR阳性表达,显示OECs仍然存活,且与宿主组织整和良好;部分再生轴突长入断端间组织,呈MBP阳性表达。结论人胚胎OECs对成鼠胸髓损伤后的轴突再生有促进作用。