摘要:

SUBPOPULATIONS of olfactory receptor neurons, which are dispersed throughout the olfactory neuroepithelium, express specific cell surface carbohydrates and project to discrete regions of the olfactory bulb. Cell surface carbohydrates such asN-acetyl-lactosamine have been postulated to mediate sorting and selective fasciculation of discrete axon subpopulations during development of the olfactory pathway. Substrate-boundN-acetyl-lactosamine promotes neurite outgrowth by both clonal olfactory receptor neuron cell lines and olfactory receptor neuronsin vitro, indicating that cell surface carbohydrates may be ligands for receptor-mediated stimulation of axon growthin vivo. In the present study, the role of transmembrane signaling inN-acetyl-lactosamine-stimulated neurite outgrowth was examined in the clonal olfactory neuron cell line 4.4.2. Substrate-boundN-acetyl-lactosamine stimulated neurite outgrowth which was specifically inhibited by antagonists to N- and L-type calcium channels and to tyrosine kinase phosphorylation. These results indicate thatN-acetyl-lactosamine can evoke transmembrane receptor-mediated responses capable of influencing neurite outgrowth.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

WE have isolated a cDNA encoding the 5-HT4Sreceptor by RT-PCR on poly (A)+RNA from both human heart and brain. The sequence homology with the rat and mouse 5-HT4receptors was high: 93.8% of identity in the amino acid sequence. None of the 24 amino acid substitutions observed between rat and human receptors are at positions likely to modify their pharmacology. Comparing the pharmacological properties of six agonists and five antagonists on rat and human 5-HT4Sreceptors revealed no significant differences. We have analyzed the behavior of renzapride, a full and a partial agonist on mouse colliculi neurons and human heart biological responses respectively. The coupling efficiency of renzapride was two-fold lower than that of 5-HT for the stimulation of 5-HT4Sreceptors transfected in two different cell lines (LLC-PK1 and COS-7), but increasing the receptor density suppressed the partial agonist effect of renzapride.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

TO understand the properties of benzodiazepine receptor in the neostriatum, we examined the potentiating effects of diazepam, triazolam and brotizolam on the GABAAreceptor-mediated Cl−current in dissociated rat neostriatal neurones using the nystatin-perforated patch recording configuration. Neurones were classified into large and small neurones, on their somatic size. In the large neurones, which are putative cholinergic interneurones, all the benzodiazepine receptor agonists recognized a single effective site. However, in the small neurones, which are mostly considered to be projecting neurones, the effect of brotizolam was best described when two effective sites were assumed. Therefore, the properties of benzodiazepine receptor differed among large and small neurones while at least two kinds of functional binding sites were also found to exist in small neurones.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ACTIVITY-DEPENDENT changes of conduction velocity (CV) and conduction block in single Aδ fibers of primary afferent neurons were characterized in a rat model of neuropathy (NP). Injured dorsal root (DR) fiber in NP rats exhibited profoundly greater decreases of CV following impulse activity than did DR fiber in normal rats. Activity-dependent conduction block was absent up to 100 Hz of activity rate in DR fiber of NP rats, but was present above 25 Hz in normal rats. Profiles of activity dependence in sciatic fibers were similar in both NP and normal rats. These results suggest that nerve injury may alter activity-dependent hypoexcitability of Aδ DR fibers. Furthermore, this excitability change may be responsible for the elevated pain perception in neuropathy.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

HIPPOCAMPAL neurons which increase their activity when the rat passes through a certain position in the environment are called place cells. This paper describes the relationship between their temporal firing patterns and the behavior of the rat with the aim of characterizing the information they encode. The place field was identified in a circular open field during locomotion rewarded by intracranial self-stimulation of lateral hypothalamus. Detailed analysis of temporal firing patterns shows a correlation between changes in the orientation of movement trajectory and occurrence of the last firing of the burst trains emitted during passage of the animal through the place field. This suggests that some hippocampal neurons may encode the spatial information about the orientation changes in the place field.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

THE effects of β-amyloid precursor protein (β-APP) fragments on plasticity of glutamtatergic synaptic transmission were examined in the hippocampus of urethane anaesthetized rats. I.c.v. injection of β-amyloid (Aβ) 1–40 and 1–42 and the C-terminal fragment CT105 greatly shortened the duration of high frequency stimulation-induced long-term potentiation (LTP) of field excitatory postsynaptic potentials in the CA1 area. Whereas in vehicle injected animals LTP was stable over a 5 h recording period, doses of these peptides (Aβ1–40, 0.4 and 3.5 nmol; Aβ1–42, 0.01 nmol; CT105, 0.05 nmol) which did not affect baseline synaptic transmission abolished LTP within 3–5 h. The reduced duration of this form of synaptic plasticity may contribute to the cognitive deficits in Alzheimer's disease.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

INTRAPERITONEAL injection of Δ9-THC (7.5 mg/kg) in rats made tolerant to morphine by s.c. implantation of morphine pellets had a much greater analgesic effect than in placebo pellet plus Δ9-THC treatment. To investigate whether this was due to some change in cannabinoid receptor levels and/or expression induced by chronic morphine, we designed this autoradiographic binding study coupled within situhybridization on sagittal sections of the treated rat brains. Binding showed a significant increase in CB1 receptor density (15%) specifically in the caudate-putamen, in parallel with a significant enhancement of CB1 mRNA in the same area (20%). We suggest that morphine chronic treatment leads to a functional modulation between the opioid and cannabinoid systems at least for analgesia in a specific area, in this case the striatum.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

THE effect of insulin-like growth factor 1 (IGF-1) on neonatal plasticity was studied using the rat olivocerebellar projection as a model. Unilateral removal of climbing fibres in the rat before postnatal day 7 induces re-innervation of the deafferented hemi-cerebellum, which does not occur after postnatal day 10. Rats aged 11 or 12 days underwent climbing fibre transection followed by IGF-1 injection into the denervated cerebellar cortex 24 h later. The exogenous IGF-1 induced climbing fibre re-innervation of the denervated hemicerebellum in a pattern similar to that seen in the immature rat. Thus IGF-1 can extend the window of neonatal plasticity of the brain and therefore may be of potential therapeutic use post-trauma.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ANALYSIS of 139 CSF samples from living subjects, using iso-electric focusing in polyacrylamide gels, demonstrated an anomalous molecular form of acetyl-cholinesterase (AChE). This form was present in 84 of 87 patients with a clinical diagnosis of Alzheimer's disease (AD), 28 of whom have died and in whom histopathological confirmation of AD was obtained. The abnormal AChE form was also present in 22 of 23 patients with clinical dementia not regarded as AD type. In the six patients who died this abnormal AChE form was found in three cases of multi-infarct dementia, one with cerebral glioma with dementia and one with clinical dementia, but no pathology was found based on the Khachaturian criteria for AD. One patient with normal pressure hydrocephalus was negative when tested for the abnormal AChE form. This evidence indicates that the anomalous molecular form of AChE may not be specific for AD, and may possibly be a common indicator for organic dementia. The discovery of this form in 27 of 29 age-matched non-demented controls may indicate that the anomalous molecular form of AChE may not only exist in patients with clinically detectable dementia, but is probably present for a period before the onset of dementia. Recognizing and understanding the existence of pre-clinical dementia would be beneficial in designing a strategy for both the prevention and the treatment of dementia.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

INVOLUNTARY attention to auditory stimulus changes during a visual discrimination task was studied with event-related potentials (ERPs) recorded from the human scalp. A repetitive standard tone or an infrequent, slightly higher deviant tone preceded each visual target stimulus. Deviant tones elicited the mismatch negativity and P3a ERP components and caused increases in reaction time and error rate in the visual task indicating involuntary attention to an auditory stimulus change. These effects were observed even when the tones occurred simultaneously with a visual warning stimulus introduced to keep attention focused on the visual task. In the latter condition, involuntary switching of attention away from the visual task also attenuated the N1 ERP component to visual target stimuli preceded by the deviant tone.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID