摘要:

AbstractThe expression of growth‐associated protein GAP‐43 mRNA in spinal cord and dorsal root ganglion (DRG) neurons has been studied using an enzyme linkedin situhybridization technique in neonatal and adult rats. High levels of GAP‐43 mRNA are present at birth in the majority of spinal cord neurons and in all dorsal root ganglion cells. This persists until postnatal day 7 and then declines progressively to near adult levels (with low levels of mRNA in spinal cord motor neurons and 2000–3000 DRG cells expressing high levels) at postnatal day 21. A re‐expression of GAP‐43 mRNA in adult rats is apparent, both in sciatic motor neurons and the majority of L4 and L5 dorsal root ganglion cells, 1 day after sciatic nerve section. High levels of the GAP‐43 mRNA in the axotomized spinal motor neurons persist for at least 2 weeks but decline 5 weeks after sciatic nerve section, with the mRNA virtually undetectable after 10 weeks. The initial changes after sciatic nerve crush are similar, but by 5 weeks GAP‐43 mRNA in the sciatic motor neurons has declined to control levels. In DRG cells, after both sciatic nerve section or crush, GAP‐43 mRNA re‐expression persists much longer than in motor neurons. There was no re‐expression of GAP‐43 mRNA in the dorsal horn of the spinal cord after peripheral nerve lesions. Our study demonstrates a similar developmental regulation in spinal cord and DRG neurons of GAP‐43 mRNA. We show moreover that failure of re‐innervation does not result in a maintenance of GAP‐43 mRN

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00115.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractWe have previously shown that the neural adhesion molecules L1 and N‐CAM influence second messenger systems when triggered with specific antibodies at the surface of the phaeochromocytoma PC12 cell line (Schuchet al., Neuron,3, 13–20, 1989). To determine whether the two molecules are linked to the same intracellular signalling cascades, independent of the cell type expressing them, or whether different neural cell types respond with different signal transduction mechanisms, we have investigated the effects of antibodies to L1 and N‐CAM, and the isolated molecules themselves, on second messenger systems in different neural cell types. We have investigated cultures of cerebellar and dorsal root ganglion neurons and transformed Schwann cells and related these results to those obtained with the PC12 cell line. Here we show that addition of L1 and N‐CAM antibodies and the isolated molecules themselves elicit cell type‐specific responses that can be modulated by the substrate on which the cells are maintained. Depending on the cell type, cells respond to the triggering of L1 and N‐CAM with antibodies, or addition of the purified molecules, by either up‐regulation or down‐regulation of inositol phosphate turnover, by a rise in intracellular Ca2+levels dependent on or independent of the opening of voltage‐gated Ca2+channels, or by an increase or decrease in intracellular pH. Moreover, cerebellar neurons expressing N‐CAM respond to addition of N‐CAM, but not to N‐CAM antibodies, in contrast to the other neural cell types studied, which respond to both triggers. Furthermore, cerebellar neurons were the only cells to show a rise in cAMP levels in response to any of the ligands tested. This stimulation of cAMP production by L1 antibodies depended on the cross‐linking of L1 molecules at the cell surface, whereas the other responses did not depend on clustering of L1. Simultaneous addition of L1 and N‐CAM antibodies either elicited an additive or more than additive effect on the intracellular responses which, for cerebellar neurons, depends on the substrate on which the cells are maintained. These observations indicate that L1 and N‐CAM or their antibodies activate cell type‐specific intracellular signalling systems and that the two molecules can act interdependently

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00116.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractAlthough substantial evidence exists for the involvement of growth‐associated protein‐43 (GAP‐43) in neuronal development and regeneration, the precise role of this protein in neurite outgrowth is currently debated. To investigate the role of GAP‐43 in the initiation of neurite outgrowth, we transfected a full‐length cDNA coding for GAP‐43 into a mouse neuroblastoma cell line (Neuro‐2a) which can be differentiated to a neuronal phenotype using retinoic acid (RA). We show that the consequent overexpression of GAP‐43 results in a change in the basic morphology of these cells, but is not in itself sufficient to induce the extension of neurites. However, overexpression of GAP‐43 results in a marked acceleration of neurite formation in response to RA. We propose that while GAP‐43 does not trigger the initiation of neurite extension, its expression is rate‐limiting for neurite outgrowth in response to differentiat

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00117.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe pattern of distribution of SP40,40‐like immunoreactive structures has been studied in the rat brain using a well‐characterized polyclonal antibody raised against the SP40,40 protein. Protein SP40,40 is the human counterpart of the rat sulphated glycoprotein 2, whose mRNA shows widespread expression in the developing and mature brain. In young adult rats few immunoreactive structures were observed. Some immunoreactive neurons were found in the cingulate cortex, the arcuate and perifornical hypothalamic nuclei, as well as glial labelling in the hypothalamus. A striking increase in the number of immunoreactive cells was observed as a function of age. In 20–22‐month‐old rats, numerous immunoreactive cells were observed in the cingulate cortex, several thalamic and hypothalamic nuclei, the red nucleus, olivary nuclei, superior colliculus, and many cranial nerve nuclei. Whereas the immunoreactivity was restricted to a diffuse labelling of the cell bodies and processes in young rats, other forms of labelling were observed in aged rats: punctate cytoplasmic labelling and intensely stained granules with no visible cell membrane. A further increase in the density of the immunoreactive material was observed in 30–31‐month‐old rats. Double labelling experiments demonstrated that the SP40,40 immunoreactivity was almost exclusively located in neurons and not in glial cells (with the exception noted above). The distribution of SP40,40 immunoreactivity in aged rats did not coincide with the distribution of the microtubule‐associated tau protein, O

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00118.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractWe have studied the effects of tetanic stimulation of the corticostriatal pathway on the amplitude of striatal excitatory synaptic potentials. Recordings were obtained from a corticostriatal slice preparation by utilizing both extracellular and intracellular techniques. Under the control condition (1.2 mM external Mg2+), excitatory postsynaptic potentials (EPSPs) evoked by cortical stimulation were reversibly blocked by 10 μM 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX), an antagonist ofdl‐α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA) ionotropic glutamate receptors, while they were not affected by 30–50 μM 2‐amino‐5‐phosphonovalerate (APV), an antagonist ofN‐methyl‐d‐aspartate (NMDA) glutamate receptors. In the presence of 1.2 mM external Mg2+, tetanic activation of cortical inputs produced long‐term depression (LTD) of both extracellularly and intracellularly recorded synaptic potentials. When Mg2+was removed from the external medium, EPSP amplitude and duration increased. In Mg2+‐free medium, cortically evoked EPSPs revealed an APV‐sensitive component; in this condition tetanic stimulation produced long‐term potentiation (LTP) of synaptic transmission. Incubation of the slices in 30–50 μM APV blocked striatal LTP, while it did not affect LTD. In Mg2+‐free medium, incubation of the slices in 10 μM CNQX did not block the expression of striatal LTP. Intrinsic membrane properties (membrane potential, input resistance and firing pattern) of striatal neurons were altered neither by tetanic stimuli inducing LTD and LTP, nor by removal of Mg2+from the external medium. These findings show that repetitive activation of cortical inputs can induce long‐term changes of synaptic transmission in the striatum. Under control conditions NMDA receptor channels are inactivated by the voltage‐dependent Mg2+block and repetitive cortical stimulation induces LTD which does not require activation of NMDA channels. Removal of external Mg2+deinactivates these channels and reveals a component of the EPSP which is potentiated by repetitive activation. Since the striatum has been involved in memory and in the storage of motor skills, LTD and LTP of synaptic transmission in this structure may provide the cellular substrate for motor learning

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00119.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractDay‐old domestic chicks (Gallus domesticus) were trained on a one‐trial passive avoidance task in which the aversive stimulus was an unpleasant tasting substance, methyl anthranilate. Thirty minutes later, localization ofN‐methyl‐d‐aspartic acid (NMDA)‐sensitive [3H]glutamate receptor binding sites, [3H]MK801 and [3H]AMPA binding sites in 17 regions of the forebrain of methylanthranilate‐trained and control (water‐trained) chicks was determined using quantitative receptor autoradiography. Significant differences in binding to both MK801‐ and NMDA‐sensitive glutamate receptors, but not α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptors, were found in three regions of the forebrain of trained compared to control chicks; two of these regions have been implicated from previous lesion, biochemical and morphological studies as playing a key role in the process of memory formation and storage following passive avoidance training. For NMDA‐sensitive [3H]glutamate receptors, significant elevations in binding were observed in two regions, the left intermediate and medial hyperstriatum ventrale (IMHV) (39%) and the lobus parolfactorius (LPO) (34%), at 30 min post‐training, but a decrease (44%) occurred in binding to the lateral neostriatum. Significant increases in binding to MK801 receptors were observed in the left IMHV (19%) and right IMHV (13%), and left LPO (22%) at 30 min post‐training, though there was a decrease in the right LPO (15%). These findings, coupled with those described in a previous paper from our group (Burchuladze and Rose,Eur. J. Neurosci.,4, 533–538, 1992), demonstrate that a glutamate receptor subtype is involved in

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00120.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractSixteen clones, recently isolated from the PC12 nerve cell line, were analysed for a variety of markers and activities. Two endoplasmic reticulum (ER) luminal markers, the chaperone protein BiP and the major Ca2+storage protein calreticulin, as well as the 40‐kD rough ER membrane marker and the plus‐end‐directed mirotubule motor protein, kinesin, were found to be expressed at similar levels. These results suggest that the size of the ER, the function of microtubules and the capacity of the rapidly exchanging Ca2+store do not change substantially among the clones. Other proteins expressed at comparable levels were synapsin I and IIa, members of a nerve cell‐specific protein family known to bind synaptic vesicles to the cytoskeleton. In contrast, another ER membrane protein, calnexin, and the markers of secretory organelles were found to vary markedly. One clone (clone 27) completely lacked both chromogranin B and secretogranin II, the proteins contained within dense granules, and synaptophysin, a marker of clear vesicles. Other clones expressed these markers to variable and apparently mutually unrelated levels. Marked variability was observed also in the uptake of exogenous catecholamines, in their release both at rest and after stimulation, and in nerve growth factor‐induced differentiation. These results provide indirect information about the mechanisms that regulate the expression of structures and activities in PC12 cells. Of particular interest is clone 27, which appears globally incompetent for regulated secretion and might therefore be a valuable tool for the study of this activity in a n

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00121.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe aim was to study the regulation of μ and δ opioid binding sites in the superficial layers (laminae I–II) of the dorsal horn of the adult rat spinal cord 1, 2, 4 and 12 weeks after unilateral dorsal rhizotomies of various extents. Using quantitative autoradiography and highly selective tritiated opioid ligands, we have shown that the decrease in [3H]Tyr*‐d‐Ala‐Gly‐NMe‐Phe‐Gly‐ol ([3H]DAMGO) (μ sites) and [3H]Tyr*‐d‐Thr‐Gly‐Phe‐Leu‐Thr ([3H]DTLET) (δ sites) binding in the side ipsilateral to the lesion as compared to the intact side is related to the number of dorsal roots cut. In the segment central to the lesion, 1 week after the lesion, ipsilateral/contralateral side binding ratios for [3H]DAMGO were 0.70, 0.49, 0.36 and 0.25 when 1, 3, 5 and 7 roots respectively were sectioned. For [3H]DTLET, the ratios were 0.71, 0.54, 0.42 and 0.39. The time‐related analysis of binding ratios showed that, in partially deafferented spinal segments after long‐term deafferentation (12 weeks postlesion) there were greater numbers of μ and δ binding sites than in cases of short‐term deafferentation (1–2 weeks). By contrast, in spinal segments considered as completely deafferented, there was no difference in the remaining μ and δ binding sites at 12 weeks as compared to 1 week postlesion. Consequently, it is deduced that the partial recovery of μ and δ binding observed after long‐term partial deafferentation could be associated with neuronal plasticity (probably collateral sprouting) of fine diameter primary a

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00122.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractIn previous studies we have shown that aspiration lesions centred on lobule HVI in the cerebellar cortex of rabbits produce a profound loss of conditioned nictitating membrane (NM) responses. Because aspiration lesions of the cerebellar cortex cause retrograde degeneration in precerebellar nuclei we tested in rabbits whether excitotoxic lesions of the cerebellar cortex that spare these precerebellar nuclei also cause a loss of conditioned NM responses. Following discrete injections of kainic acid into HVI and rostral regions of the adjacent folia of crus I and crus II, we observed an immediate loss of conditioned NM responses. Following extensive retraining several subjects showed a gradual recovery of conditioned responses. But subjects with the most complete lesions never recovered more than a few conditioned responses. Kainic acid lesions did not change ipsilateral unconditioned reflex responses to a range of stimulus intensities. The kainic acid injections caused obvious degeneration of Purkinje and granule cells but not of the precerebellar nuclei. We conclude that HVI and parts of crus I and crus II are essential for normal retention of conditioned NM responses.

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00123.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe efferent (olivocochlear) nerve supply to the cochlea is subdivided into a lateral and a medial innervation according to several criteria, e.g. locus of origin in the superior olivary complex and type of synaptic connections established in the organ of Corti. We have used a triple immunofluorescence colocalization approach to determine whether putative cholinergic neurons from the lateral innervation contain both metenkephalin and calcitonin gene‐related peptide (CGRP), and whether those from the medial innervation also contain CGRP. About 80% of the choline acetyltransferase (ChAT)‐like immunostained lateral efferent neurons within the lateral superior olive were CGRP‐ and metenkephalin‐like immunostained. In the organ of Corti, colocalization of the three antigens within the inner spiral bundle was also found. This bundle contains the lateral efferent synapses, with the dendrites of the primary auditory neurons innervating the sensory inner hair cells. Most of the medial efferent neurons in the ventral nucleus of the trapezoid body were only immunoreactive for ChAT. However, in the rostral part of the nucleus, a minority of ChAT‐like immunostained neurons were also CGRP‐like immunostained. None of the ChAT‐like immunostained medial efferent neurons presented metenkephalin‐like immunostaining. In agreement with these brainstem data, partial colocalization of the ChAT‐ and CGRP‐like immunostaining and a lack of metenkephalin immunoreactivity was noted below the sensory outer hair cells, which are the synaptic targets of medial efferent terminals in the organ of Corti. This distinction in the coexistence pattern of the two efferent innervations probably reflects distinct modes of action for acetylcholine in the cochlea. In one case, the effects of acetylcholine on the primary auditory neurons innervating the inner hair cells may require balanced modulation by metenkephalin and CGRP. In the other case, modulation of the effects of acetylcholine on the outer hair cells by neuropeptides wou

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00124.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY