摘要:

ELECTROMYOGRAPHIC responses (EMGs) of limb muscles were studied during microiontophoretic application of 5-hydroxytryptamine (5-HT) into the lateral vestibular nucleus (LVN) or the spinal vestibular nucleus (SpVe) of anaesthetized rats. The aim was to ascertain whether the level of 5-HT in these nuclei was able to modulate muscle responsiveness. Increased levels of 5-HT in LVN (and to a weaker extent in SpVe) enhanced the EMGs of proximal extensor muscles and depressed those of flexors. The 5-HT2Areceptor antagonist ketanserin, applied into the LVN, prevented 5-HT effects on EMG-evoked responses. It is concluded that 5-HT can modulate the motor output via the vestibulospinal pathway, exerting a differential control over flexor and extensor muscles.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE used isolated IgG antibodies selective for P2X3receptors to study the ultrastructural distribution of these receptors in rat sensory neurons. In trigeminal ganglia, P2X3receptor immunoreactivity occurred in small and large nerve cell bodies and their processes. Endoplasmic reticulum and Golgi apparatus were heavily stained; cytoplasmic matrix was faintly to moderately stained. In synaptic glomeruli in lamina II of cervical dorsal horn, P2X3receptor-immunoreactive core terminals were post-synaptic to unlabelled vesicle-containing dendrites and axons. In the nucleus of the solitary tract, receptor-positive boutons synapsed on dendrites and cell bodies and had complex synaptic relationships with other axon terminals and vesiculated dendrites. These observations identify sites from which ATP could be released to influence sensory signalling within the central nervous system.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE sensation of a single sound event can be altered by subsequent sounds. This study searched for neural mechanisms of such retroactive effects in macaque auditory cortex by comparing neural responses to single tones with responses to two consecutive tones. Retroactive influences were found to affect late parts of the response to a tone, which comprised 53/134 of the recordings of action potentials and 88/131 of the recordings of field potentials performed in primary, caudal, and medial auditory fields. If before or during the occurrence of the late response to the first tone a second tone was presented the late response was suppressed. Suppression of late cortical responses parallels perceptual phenomena like backward recognition masking, suggesting that suppression of late responses provides a neural correlate of auditory backward effects.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE goal of this study was to determine the topographical and temporal specificity of neuronal and vascular responses using an intraoperative optical technique (iOIS). The face, thumb, index, and middle fingers were stimulated individually to obtain separate maps of cortical activation. Peak optical responses provided unique, non-overlapping cortical brain maps. Non-peak signals were more dispersed and produced overlapping responses from different digits. Peak iOIS responses colocalized with electrocortical stimulation mapping and evoked potentials. Temporally, we observed statistically significant specificity corresponding to sequential cortical activation during early optical signals (500–1750 ms), but later perfusion responses were non-specific. To our knowledge, this is the first report of either topographical specificity in overlapping spatial patterns, and/or temporal specificity in early perfusion profiles. These results therefore may have significant implications for other perfusion dependent functional imaging techniques.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

EUROPROTECTIVE effects of estrogen have been demonstrated against a variety of cytotoxic insults. We present data here addressing a possible mechanism of estrogen neuroprotection in the human teratocarcinoma cell line NT2 terminally differentiated to a neuronal phenotype. Cell death induced by H2O2or glutamate results in a dose-dependent cell death of NT2 neurons, while 24 h of estrogen pretreatment significantly enhances neuronal viability. Bcl-2 expression has been shown to reduce oxidative stress and prevent cell death. In NT2 neurons, Bcl-2 levels are dramatically elevated upon differentiation and are further enhanced with estrogen treatment. These results suggest that neuroprotective effects of estrogen may be related to increases in Bcl-2 expression.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

OVERFLOW of the neurotransmitter dopamine (DA) in striatum is implicated in the neurodegenerative processes in ischemia, hypoxia and local exposure to high concentrations of excitatory amino acids. However, how DA causes neurotoxicity is not understood. We report that intrastriatal injection of DA (0.5–1 μmol/μl) in Wistar rats produces a robust increase in apoptotic cell death as determined by both a terminal deoxynucleotidyl transferase catalyzed dUTP-biotin nick labeling (TUNEL) and Klenow polymerase catalyzed [32P]dCTP labeled DNA ladder. Cells in which apoptosis was induced by DA are characterized by condensed chromatin, DNA fragmentation, shrinkage and irregular shapes. The apoptotic cell death induced by DA is not due to the effect of hyperosmolar solution since intrastriatal injection of identical concentrations of NaCl on opposite sides of the same rat brains shows little TUNEL-positive labeling. The number of apoptotic cells is proportional to the amount of DA and length of exposure period. With DA concentrations from 0 to 1 μmol/μl, the maximal toxic effect appears at a concentration of 1 μmol/μl after 24 h exposure. Demonstration of DA-induced apoptosisin vivomay provide a potential molecular mechanism for DA neurotoxicity.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

USING immunoelectron microscopy we have investigated the presence of somatostatin in normal bone and joint tissues. We observed somatostatin labeling in the myelinated nerve fibers of the periosteum, the bone marrow cells and in the mature bone matrix but only slightly in the synovial cells. Quantification of somatostatin in bone tissue by radioimmunoassay showed highest levels in bone marrow followed by periosteum and cortical bone. These findings suggest a role for somatostatin in bone and joint physiology.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

C6 glioma strongly express nitric oxide synthase. Rats bearing C6 tumours were pre-treated with i.v. Ng-nitro-L-arginine methyl ester (L-NAME), 3-morpholinosydnonimine (SIN-1) or saline before local cerebral blood flow (LCBF) or tumour capillary permeability (TCP) was measured by the [14C]iodoantipyrine autoradiographic or [14C]α-amino-isobutyric acid techniques. L-NAME and SIN-1 caused significant TBF alterations (−44% and +136%, respectively) with less marked (−15% and +33%) alterations in normal brain. Calculated cerebrovascular resistance changes within tumour were indeed selective. Baseline TCP was increased compared with normal brain (20-fold). L-NAME and SIN-1 administration did not alter TCP. These effects have significant implications for human malignant glioma management. Selective i.v. manipulation of LCBF, without significant changes in TCP, could increase the efficacy of chemotherapy, radiotherapy or provide better peritumoural oedema control.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IMMATURE glia may not be able to buffer K+ions released during neuronal activity. Therefore, we investigated entorhinal-hippocampal slices of juvenile rats (ages P15–18 and P22–26) using a perfusion medium containing 2 mM BaCl2in order to block glial inward rectifying and leak potassium channels. In contrast to adult animals, rises in [K+]oin slices from juvenile animals elicited by repetitive alvear stimulation were not augmented by Ba2+. Ba2+effects on fast field potentials, slow field potentials and the applied current sink source distribution were roughly similar as in adult rats. We conclude that the capacity to buffer large quantities of K+ions by mechanisms involving Ba2+-sensitive K+channels has not yet developed in juveniles.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE investigated the effects of heat shock on the temperature sensitivity of synaptic transmission in the motor circuit for flight inLocusta migratoria. In heat shocked animals synaptic transmission failed at 5–6°C higher than in control animals and recovery of transmission was more than three times faster upon return to room temperature. We also found that synaptic delay was rendered insensitive to increases in temperature by heat shock. Thus we have shown in the locust that heat shock has important protective effects on synaptic transmission, thereby extending the upper temperature limit for the motor patterns that generate flight. This is the first description of an effect of heat shock that preserves neuronal communication under subsequent stressful conditions.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID