摘要:

THE cloning and pharmacological characterization of mouse 5-HT1Dreceptors as well as the comparative analysis of its embryonic expressionvsthat of 5-HT1Breceptors are reported. High densities of both 5-HT1Dreceptors mRNA and specific 5-HT1Dbinding sites were detected at 8, 9.5, 10.5 and 13.5 days of prenatal development. In contrast, no specific 5-HT1Bbinding sites could be detected until 13.5 days of development, when they were present at lower levels than 5-HT1Dreceptors. This differs markedly from the situation in the adult brain, in which 5-HT1Breceptors are present at a much higher density than the 5-HT1Dsubtype. These data suggest the involvement of 5-HT1Dreceptors in the mitogenic and proliferative effects of serotonin during early embryonic development.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

SPATIO-TEMPORAL gaze behaviour patterns were analysed as normal participants wearing a mobile eye tracker approached and stepped over obstacles of varying height in the travel path. We examined the frequency and duration of three types of gaze fixation with respect to the participants' stepping patterns: obstacle fixation (ObsFix); travel fixation (TravFix) (when the gaze is stable and travelling at the speed of whole body) and fixation in the 4–6 m region (Fix4–6). During the approach phase to the obstacle, participants fixated on the obstacle for ∼20% of the travel time. Only Fix4–6 duration was modulated as a function of obstacle height by regulating the frequency and reflected the increased time needed for detection of the small low contrast obstacle in the travel path. Frequency of ObsFix increased significantly as a function of obstacle height and reflected visuo-motor transformation needed for limb elevation control. Participants did not fixate on the obstacle as they were stepping over, but did the planning in the steps before. TravFix duration and frequency was constant while Fix4–6 duration was higher in the step before and step over the obstacle reflecting visual search of the landing area for the lead limb following obstacle avoidance. These results clearly show that obstacle information provided by vision is used in a feed-forward rather than on-line control mode to regulate locomotion. Information about self-motion acquired from optic flow during TravFix can be used to control velocity of locomotion.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

WE tested the hypothesis that activation of metabotropic glutamate receptors (mGluR) might contribute to the depression of excitatory postsynaptic potentials during hypoxia. The experiments were performed on hippocampal slices taken from young (12–14 days old) Wistar rats. The depression induced by hypoxia (14 min) was not modified in the presence of either the non-selective mGluR antagonist (which blocks mainly group I and II mGluR), MCPG (500 μM) or the selective group III mGluR antagonist, MPPG (500 μM). However, in experiments performed in the presence of the selective adenosine A1receptor antagonist, DPCPX (50 nM), part of the hypoxia-induced depression could be prevented by MPPG (500 μM). Activation of group III mGluR may contribute to the hypoxia-induced depression, but this contribution is only revealed when adenosine A1receptors are blocked.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

SINGLE channel activity of expiratory neurones was studied in outside-out recordings. Expiratory neurones were identified in the ventrolateral region of thein vitroisolated brain stem–spinal cord preparation of newborn rats in cell-attached and whole-cell configurations by their pattern of firing related to phrenic motor output. Three potassium (K+) channels of 10, 30 and 70 pS exhibited steady-state activity during long voltage commands (up to 5 min) and could be found associated together in the same patches. The 30 pS channel showed voltage dependency, being most active at small depolarizations. The 70 pS channel showed little activity with <1% of openings per sample time and 1 mM tetraethylammonium (TEA) sensitivity. At similar concentrations, the discharge of the phrenic nerve was also altered, as shown by the increase of the respiratory frequency and a tonic discharge. The association of these K+channel types on the same patches may be specific of respiratory neurones and could contribute to their bursting activity.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

WE have developed in new-born mice a ventral tilted-horizontal slice preparation for pontine stimulation and recording of spontaneous respiratory-like rhythmic trains of glutamatergic excitatory postsynaptic potentials (EPSPs) in medullary neurons. Electrical stimulations (10–50 Hz for 100–500 ms) of the caudal pontine reticular formation triggered a burst of EPSPs, recycling of the rhythmic activity and persistent increase of the rhythmic behaviour. These results identify a ventral pontine pathway that promotes rhythm generating mechanisms in the medulla and probably derives from a population of lateral reticular neurons identified in the embryonic hindbrain and eliminated after inactivation of the early developmental geneKrox-20.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

NEUROFIBRILLARY tangles and neuropil threads, both made of hyperphosphorylated tau proteins, point to an alteration of microtubules in Alzheimer's disease. The aim of this study was to test the consequences of these lesions on axoplasmic flow, which is dependent on intact microtubule assembly. We assessed the transport of synaptic proteins from the neuronal cell body to axonal terminals, using SNAP-25 (synaptosomal-associated protein of 25 kD) immunohistochemistry as a marker of impaired axonal transport. A sample from the supramarginalis gyrus was obtained from 29 individuals over 75 years of age whose cognitive function had been prospectively assessed. Accumulation of immunoreactive material in swollen axons was observed in the white matter of severely demented individuals, and their number was correlated with the density of neurofibrillary tangles (r = 0.53, p = 0.005) and of focal Aβ deposits (r = 0.61, p = 0.001). This supports the hypothesis of a dysfunction of the cytoskeleton in Alzheimer's disease. An unexpected finding was the lack of correlation between SNAP-25 immunohistochemistry in the grey matter and the intellectual status or the density of neurofibrillary tangles, focal Aβ deposits and neuronal profiles. These results which question the role of synaptic markers as correlates of dementia, should be extended to other brain areas.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

STATHMIN (p19) is developmentally regulated as a neural-enriched phosphoprotein associated with neurite outgrowth and synaptic formation during cell proliferation and differentiation, and remains highly abundant in adult rat brain. Whether stathmin is involved in injury-induced reactive synaptogenesis in adult rat was examined in this study. Following unilateral cortical lesion, a significant increase in stathmin mRNA expression was found in the cells of contralateral homotypic cortex and in the subventricular zone of the lateral ventricle. This increase coincided in time with the corticostriatal axon sprouting and synaptic remodeling previously found in denervated striatum. Our data suggest that stathmin plays an important role in regulation of reactive synaptogenesis in adult brain.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

TIME-RESOLVED fMRI seeks to elucidate neuronal activity during a single execution of a mental task, which corresponds typically to a timescale of seconds. However, this is also the timescale of the hemodynamic response, which delays and blurs the signal in time. In order to distinguish the temporal characteristics of the neuronal activity from that of the hemodynamic response, which is often vaguely known, we recorded a set of fMRI time courses under conditions of a varying behavioral parameter, and correlated this parameter to the width of the fMRI response. For the task under investigation, the mental rotation of three-dimensional objects, we found that the activation in the parietal lobe is related to an aspect of the task that is described by the reaction time (for example, the very act of mental rotation), and not only to aspects of the task that are constant from trial to trial, such as the visual presentation at the beginning or the decision at the end of the task.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

GROWTH hormone-releasing hormone (GHRH) and β-endorphin are mainly synthesized in neurones of the hypothalamic arcuate nucleus. Arcuate neurones also contain both ionotropic and metabotropic glutamate receptors. The aim of present study was to investigate whether glutamate receptors are present in GHRH and β-endorphin containing nerve cells of this hypothalamic area. Using double-label immunocytochemistry as well as the mirror technique, we found that almost all GHRH and β-endorphin immunoreactive arcuate neurones contain the metabotropic glutamate receptor 1a. The observations provide morphological evidence for the view that glutamate, which appears to be a major excitatory neurotransmitter in the hypothalamus, may directly stimulate GHRH and β-endorphin neurones of the medial hypothalamus.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

MONOCLONAL antibody MN423 stains all hallmarks of tau neurofibrillary pathology in Alzheimer's disease (AD), without reacting with full-length tau. It recognizes tau molecules which are cleaved at Glu-391, suggesting that tau is endogenously truncated in AD brains. We investigated whether truncation of tau takes place in pre-tangle neurones. Our results showed that tau truncation occurs inside AD neurones in the absence of other signs of AD neurofibrillary pathology. Usingin situend labelling (ISEL) of DNA we found evidence for DNA fragmentation in a significant subpopulation of MN423-positive neurones. Our results therefore suggest that tau truncation is an early intracellular event preceding cell death in AD.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID