摘要:

PRESYNAPTIC depolarization of trigemino-thalamic (TGT) terminals may contribute to modulation of ascending oro-facial somatosensory information during active (or rapid eye movement) sleep. The relative excitability of TGT terminals was inferred from changes in the current required to maintain an antidromic firing probability of 50% (EC50) during quiet wakefulness as compared to active sleep. Depolarization or hyperpolarization of TGT terminals was defined as a decrease or increase, respectively, in the EC50. Overall, the EC50of 8 TGT terminals was reduced by a mean 8.8 ± 3.6 μA during active sleep relative to quiet wakefulness. This result suggests that depolarization of TGT terminals, which may act to suppress the transfer of sensory information from the trigeminal nucleus to the thalamus, occurs during active sleep.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IMMUNOHISTOCHEMICAL studies have shown nitric oxide synthase (NOS)-positive neurons in the dorsolateral sector of periaqueductal gray (PAG), a neural site known to be critical for the expression of defensive responses. In the present study, we first characterized the dorsal PAG (dPAG) NOS, and then examined NOS activity and cyclic GMP (cGMP) accumulation in the dPAG of rats exposed to a predator (cat) for 15 min. NOS activity evaluated by enzymatic conversion of [3H]arginine to [3H]citrulline in dPAG of exposed rats increased 14.6% and the cGMP radioimmunoassay showed an increase of 30.6% in relation to non-exposed rats. These results suggest an involvement of the NO/cGMP pathway in the dPAG during defensive responses.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

CEREBROSPINAL fluid (CSF) amino acid neurotransmitter concentrations in 23 patients with acute encephalitis were compared with those in patients with acute brain infarction, multiple sclerosis and controls. The concentration of glutamate was significantly higher in encephalitis (5.2±6.7 μmol/l) and stroke patients (9.6 ±14.2 μmol/l) than in MS patients (1.6 ± 0.9 μmol/l) and controls (1.7 ± 0.8 μmol/l;p< 0.001). The concentration of glycine was significantly higher in encephalitis (11.0 ± 4.7 μmol/l) than in stroke (7.6±3.2 μmol/l) and MS patients (6.3 ± 2.1 μmol/l) or controls (5.6±1.8 μmol/l;p< 0.002). Taurine levels were significantly lower in encephalitis patients than in the other groups (p= 0.04). The correlation of high glutamate levels with poor outcome was almost significant (Kendall tau 0.63,p= 0.06). Our observations suggest that exicitotoxic neurotransmission may play an important role in the series of events that lead to neuronal damage in encephalitis.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

INXenopu soocytes coinjected with poly(A)+RNA derived from the rat cerebellum and cRNAs for the cloned G protein-gated inwardly rectifying K+channel (GIRK), GIRK1 and GIRK2, the GABA-B agonist baclofen elicited inwardly rectifying K+currents. The inward K+currents elicited by baclofen were inhibited by the selective GABA-B antagonists 2–OH saclofen and CGP 35348, and by the GIRK inhibitor Ba2+. In contrast, baclofen caused no currents in oocytes injected with the cerebellar poly(A)+RNA alone, the poly(A)+RNA and cRNA for GIRK1 or GIRK2, or only cRNAs for GIRK1 and GIRK2. These findings indicate that GABA-B receptors in the rat cerebellum were functionally expressed inXenopu soocytes and activated the cloned GIRKs composed of GIRK1 and GIRK2 as heteromultimers.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THIS study provides direct evidence from measurements of its metabolites, NO2−and NO3−, that NO is released in the spinal cord during central sensitization. A micro-dialysis fiber was implanted in the dorsal horn at L5 for collecting dialysate and administering drugs. Dialysate was pumped through a cadminum reducing column, a post-column derivatizing unit, and then a u.v. detector. After injection of capsaicin into one hind foot, NO2−increased in the dialysate. Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME) significantly reduced NO release induced by a second injection of capsaicin into the opposite foot. This supports the ideas that NO is involved in central sensitization in the spinal cord and contributes to hyperalgesia and allodynia following capsaicin injection.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BCL-2, a protein which negatively modulates apoptosis, is up-regulated by estrogen in several tissues. To determine the effect of estradiol on Bcl-2 in the adult brain, its immunoreactive distribution was examined in the hypothalamic arcuate nucleus of female rats under different endocrine conditions. The number of Bcl-2–immunoreactive neurons was significantly increased (p< 0.001) on the day of estrus compared with proestrus, diestrus and metestrus, was decreased by ovariectomy and showed a dose–response increase after estradiol administration to ovariectomized rats. Progesterone, when injected simultaneously with estradiol, reduced the effect of estradiol. These findings indicate that ovarian hormones regulate Bcl-2 in hypothalamic neurons and suggest that this protein may be involved in the neuro-protective effects of estrogen.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE photostimulation of nerve cells using a caged compound is very useful because it is non-invasive and non-destructive compared with standard electrophysiological techniques. There are no methods, however, for continuously measuring the photo-uncaged ‘free’ compound concentration at high temporal and spatial resolutions which can detect how much uncaged compound has been applied to cells. Here, we used an electrochemical detection method for the real-time measurement of photo-uncaged glutamate. In this way, we were able to determine the amount of uncaged glutamate and investigate neural activities by tracing [Ca]iwhile simultaneously employing photostimulation and on-line glutamate measurement. The combination of an on-line sensor and laser-photostimulation with [Ca]imeasurement could be a powerful tool with which to investigate synaptic connections and activities.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE describe a technique for mapping out human somatosensory cortex using functional magnetic resonance imaging (fMRI). To produce cortical activation, a pneumatic apparatus presented subjects with a periodic series of air puffs in which a sliding window of five locations moved along the ventral surface of the left arm in a proximal-to-distal or distal-to-proximal direction. This approach, in which the phase-delay of the stimulus can be used to produce somatotopic maps of somatosensory cortex, is based on a method used to generate retinotopic maps of visual cortex. Functional images were acquired using an echoplanar 1.5T scanner and a T2*-weighted spiral acquisition pulse sequence. The periodic series of air puffs created phase-related activation in two cortical regions of the contralateral parietal lobe, the posterior bank of the central sulcus and a more posterior and lateral region.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE human homologue of area V5A of rotation–selective cells in the monkey medial superior temporal area (MST) was identified using functional magnetic resonance imaging (fMRI). It was located within the border region of occipito-temporo-parietal cortex, in four of 10 subjects on both sides, and on the right or left side in three subjects each. The stimulus was a black-and-white sine-modulated windmill presented either stationary or in rotation phases of s duration. Areas V1–V3 did not show up with this paradigm. Focusing attention by mentally counting the number of rotation phases ensured high signal intensity in V5A, whereas moving attention away by counting electric stimuli to the wrist diminished it despite persistent fixation of gaze to the centre of the windmill.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE human apolipoprotein (apo) E4 isoform is associated with an increased risk for Alzheimer's disease (AD) and poor prognosis after acute CNS injury. Addition of human apoE inhibits murine microglial activation in culture, suggesting that microglia might be an important physiological target of apoE. In the present study, we examined the role of endogenous murine apoE in modulating microglial nitric oxide (NO) production following lipopolysaccharide (LPS) stimulation. Brain cultures from apoE-deficient mouse pups showed enhanced NO production relative to cultures from wild-type mice and from transgenic mice expressing the human apoE3 isoform, demonstrating that endogenous apoE produced by glial cultures is capable of inhibiting microglial function. ApoE produced within the brain may suppress microglial reactivity and thus alter the CNS response to acute and chronic injury.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID