摘要:

PRIOR studies have shown that macrophages are recruited to sites of injury or infection in the sensory organs of the inner ear, but the effects of macrophages and their cytokine secretory products on the sensory structures of the ear are not known. In the present study, cultures of dissociated statoacoustic neurons were incubated with selected macrophage secretary products and the numbers of surviving neurons after 48 hin vitrowere quantified. Results indicate that two macrophage secretary products, interleukin 1 and fibroblast growth factor 2, can enhance the survival of statoacoustic neurons, while another cytokine, tumour necrosis factor-α can diminish the survival of those neurons. Also, numerous macrophages were present in both cytokine-treated and control cultures. The findings suggest that macrophages may influence the survival of the sensory neurons of the inner ear.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

HEAD posture and neck muscle activity (EMGs) were examined in unilateral (UL) and bilateral (BL) vestibularly lesioned rats in hypergravity (1.7g.) and hypogravity (0g.) during parabolic flights. Compared with BL rats taken as control, the head and the body of UL deviated toward the lesion side at 0g. and toward the intact side at 1.7g. Recorded in head fixed condition, left and right EMGs remained symmetrical in BL while UL rats displayed an asymmetry between left and right muscles at 1.7g, but not at 0g. These results demonstrate that an experimental otolithic asymmetry, compensated on Earth, can become unbalanced in altered gravity. Paradoxically, the utricular system appears to play a major role in that process.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

FRONTAL midline theta rhythm (Fm&thetas;) is a distinct theta activity of EEG in the frontal midline area that appears during concentrated performance of mental tasks in normal subjects and reflects focused attentional processing. To tomographically visualize the source current density distributions of Fm&thetas;, we recorded Fm&thetas; by using a 64-channel whole-head MEG system from four healthy subjects, and applied a new analysis method, synthetic aperture magnetometry (SAM), an adaptive beam forming method. Fm&thetas; was observed in the MEG signals over the bilateral frontal regions. SAM analysis showed bilateral medial prefrontal cortices, including anterior cingulate cortex, as the source of Fm&thetas;. This result suggests that focused attention is mainly related to medial prefrontal cortex.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

SEVERAL neurophysiological studies have highlighted the role of the midbrain periaqueductal gray matter (PAG) in the initiation of vocalization in various animal species, from frogs to primates. With regard to humans, only two cases of complete mutism following a lesion to the PAG have been reported so far. This article describes a new case of a patient (GM) who, following an ischemic lesion to the periaqueductal gray region of the midbrain, presented with complete and irreversible mutism, though her language comprehension functions and her non-verbal expression capacity were preserved. This clinical case provides evidence that in humans the PAG also acts as a link between different vocalization-eliciting external and internal stimuli (which reach the PAG from sensory and emotional structures) and the vocal–motor coordinating mechanisms in the lower brain stem.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

The effect of the adenosine A2Areceptor agonist CGS 21680 on glutamate and aspartate release was investigated in the striatum of young and old rats by microdialysis experiments. CGS 21680 (10 μM) significantly increased glutamate and aspartate spontaneous outflow in young but not in old rats. On the contrary, CGS 21680 induced the same decrease in K+-evoked glutamate outflow in both young and aged rats. A lower dose of CGS 21680 (1 μM) failed to modify either spontaneous or K+-evoked outflow. It is suggested that the opposite effects of the A2Aagonist on excitatory amino acid outflow may be respectively mediated by striatal A2Aadenosine receptors located on glutamatergic terminals and on the striatal indirect output pathway.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

(±)CYCLAZOCINE, synthesized by Archer in 1962, was originally tested as a treatment for heroin addiction. (±)Cyclazocine is a mu opioid antagonist and kappa opioid agonist, and because of these actions, would be expected to modulate dopamine release in the nucleus accumbens as well as the reinforcing effects of drugs of abuse. In a recent study (±)cyclazocine was reported to decrease cocaine self-administration in rats. The aim of the present study was to determine whether (±)cyclazocine would alter the dopaminergic effects of nicotine that are thought to mediate its rewarding effects. Usingin vivomicrodialysis in awake and freely moving rats, we investigated the effect of (±)cyclazocine (0.5 mg/kg, i.p.) on the acute dopamine response to nicotine (0.32 mg/kg, i.v. over a 5 min period, infused 30 min later) in the nucleus accumbens. (±)Cyclazocine significantly attenuated the increase in extracellular dopamine levels induced by the nicotine infusion and enhanced nicotine-induced increases in dopamine metabolites. (±)Cyclazocine alone did not significantly affect extracellular dopamine levels. However, both the (+) and (−) enantiomers of cyclazocine did alter basal dopamine levels and these effects made it difficult to assess their individual interactions with nicotine. The results suggest that the effects of both enantiomers contribute to the effects of the racemate; (±)cyclazocine may decrease the rewarding effect of nicotine and may be the prototype of a potentially novel treatment for smoking.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Previous data show that nicotinic receptors in the ventral tegmental area are of importance for the nicotine withdrawal syndrome. Here we have investigated the specific role of α7nicotinic receptors in the ventral tegmental area for the neurobiological and behavioral consequences of nicotine withdrawal. Rats were exposed to nicotine for 14 days via s.c. osmotic minipumps. Bilateral intrategmental injections of the selective α7nicotinic receptor antagonist methyllycaconitine reduced locomotion in the nicotine-treated rats, but not in control animals. Unilateral intrategmental injection of methyllycaconitine reduced dopamine output in the ipsilateral nucleus accumbens of nicotine-treated rats, but not in controls. Our results indicate that α7nicotinic receptors in the ventral tegmental area are involved in the nicotine withdrawal syndrome.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

SOME gangliosides have been regarded as autoantigens of immune-mediated neurological disorders such as Guillain-Barré syndrome (GBS), Miller Fisher syndrome and multifocal motor neuropathy. On the other hand, proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), may be important in the pathogenesis of some neuroimmunological disorders. To clarify the interactions between immune cells and gangliosides, we investigated the effects of gangliosides on the production of proinflammatory cytokines in peripheral blood mononuclear cell (PBMC) cultures. We found that ganglioside GM2 markedly enhances the production of TNF-α and that TNF-α induction by coated GM2 is still more marked. These findings suggest that immune cells, especially monocytes/macrophages, cause inflammation upon encountering GM2.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

IN this study we investigated the long term effects of a potent and selective melanocortin 4 (MC4) receptor antagonist (HS014) on food intake, body weight, body composition and blood glucose levels in adult rats. HS014 was injected i.c.v. either by twice-daily injections (2 × 1 nmol) for 6 days or administered by continuous infusion with osmotic minipumps (0.16 nmol/h) for 2 weeks. The results show a considerable increase in food intake and body weight after both of the treatments without any signs of tachyphylaxis. After 2 weeks of treatment with osmotic pumps, the HS014-treated rats (average weight 425 g) had 20% higher body weight than the controls rats (average 360 g). When i.c.v. injections were terminated, the body weight of the twice-daily HS014-treated rats returned to the levels of control group, whereas the rats treated with continuous infusion of HS014 remained hyperphagic and still gained weight. Blood glucose levels in the rats treated with HS014 infusion were significantly increased. Analysis of body composition in HS014-infused rats indicated that body weight was increased due to fat deposits. These data show for the first time that chronic administration of exogenous MC4 receptor antagonist causes hyperphagia and severe obesity in rats. These data also indicate that the melanocortic control of food intake is very robust and suggest that changes induced by such treatment overcome negative feedback signals.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

WHEN the two eyes of an observer are exposed to conflicting stimuli, they enter into binocular rivalry and the two possible percepts will alternate in dominance. We investigated neural activity and its time course following binocular rivalry by measuring human event-related brain potentials to transitions from rivalrous to non-rivalrous stimulation. When these changes did not entail a change in conscious perception they elicited a markedly attenuated N1 component and a delayed and attenuated P3 peak as compared to percept-incompatible changes and non-rivalrous control conditions. These results suggest that in humans binocular rivalry is resolved at latest in extrastriate visual areas.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID