摘要:

THE present study tested the hypothesis that endogenous opioid peptides acting at the δ-opioid receptor (DOR) in the rostral ventromedial medulla (RVM) contribute to the antinociception elicited by the μ-opioid receptor (MOR) agonist DAMGO in the mid-brain periaqueductal gray (PAG). Following microinjection of DAMGO into the PAG, either the highly selective DOR antagonist TIPP[ψ] or the DOR2antagonist naltriben (NTB) was microinjected into the RVM. Both TIPP[ψ] (1.0 μg) and NTB (5.0 ng) significantly attenuated the analgesic effect of PAG DAMGO but had no effect when given before PAG saline. These results confirm and extend previous studies suggesting that PAG μ-opioids activate a descending system with a DOR mediated endogenous opioid link in the RVM.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

TO study the specific contribution of the D3dopamine receptor in the generation of locomotor activity, total or partially dopamine-depleted rats were pretreated with an antisense oligodeoxynucleotide for the D3receptor (D3R-as) and locomotor activity induced by apomorphine was measured. A 35.7% increase in locomotor activity was seen in the totally dopaminedepleted rats pretreated with the D3R-as, whereas the same antisense, caused a significantly greater increase in the locomotor response (95%) in the partially dopamine-depleted rats compared with control groups (pretreated with a control oligodeoxynucleotide or vehicle).In situautoradiography for D3receptors showed a 27% fall in the density of D3receptors in the islands of Calleja compared with control animals. Our results seem to confirm that D3receptors exert an inhibitory effect on locomotor activity, through the stimulation of both pre- and postsynaptic components.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

THE topographic organization of the primary somatosensory cortex adapts to alterations of afferent input. Here, electric source imaging was used to show that spatial attention modifies cortical somatosensory representations in humans. The cortical representation of the electrically stimulated digit 2 (resp. digits 2 and 3) of the right hand was more medial along the somatosensory area 3b in subjects who focused attention on digit 4 of the right hand, while it was more lateral when subjects attended digit 4 of the contralateral hand. This effect was very fast since the direction of attention was changed every 6 min. The results indicate that cortical somatosensory representations not only depend on afferent input but vary when spatial attention is directed towards different parts of the body.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

THE current study investigated whether an ipsilesional bias in line bisection, a conventional measure for diagnosing hemispatial neglect, persists even in the absence of this syndrome in patients with chronic lesions restricted to posterior association cortex or dorsolateral prefrontal cortex. Both left and right hemisphere parital lesions produced ipsilesional bisection errors, and to a comparable degree. Patients with lessions in frontal cortex, on the other hand, did not show a consistent bias. We conclude that chronic parietal lesions produce an ipsilesional bias in line bisection, even in the absence of other clinical sings of neglect, and that left hemisphere lesions can affect line bisection to the same degree as right hemisphere lesions.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

THE pathogenesis of cleft formation in schizencephaly was analyzed by examining the brain lesions produced by the infection of the Kilham strain of mumps virus during the period of neuronal migration in hamsters. Mumps virus antigen was detected in the neuroepithelial cells within the ventricular zone, the choroid plexus in the lateral ventricles, and vimentin-immunoreactive radial glial fibers. The main pathological findings were cerebral hemorrhage, neuronal necrosis, microsulci on the cerebral cortex and cleft formation through the entire thickness of the cerebral mantle. The clefts seen in these experiments were lined by embryonal elements such as neuroepithelial cells and germinal cells. Based on these results and the original definition by Yakovlev and Wadsworth, the following two conclusions were suggested. First, the mumps virus localized to the neuroepithelial cells within the ventricular zone and the radial glial fibers may induce a destructive process and subsequent anomalous neuronal migration, resulting in cleft formation. Second, the formation of the ventricular cleft extending to the pial surface, which should be complete before the cortical infolding appears, is necessary in order to produce the characteristic cleft in schizencephaly which is associated with the pial–ependymal seam.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

WE studied the possible role of neurotoxicity in the d,lamphetamine (AMPH)-induced release of acetylcholine (ACH) in the nucleus accumbens (Nac) and the involvement of endogenous NO in this process. For determination of ACH release the Nac was superfused using the push-pull-technique. NO was directly measured using the electron paramagnetic resonance technique. Repeated administration of AMPH increased ACH release by about 400%. N-nitro-L-arginine (LNNA) and 7-nitroindazole (7-NI) nearly abolished the AMPH-induced increase in ACH release. AMPH increased NO as well as lipid peroxidation (LPO) products in the cortex. L-NNA and 7-NI substantially diminished NO increase. AMPH-evoked LPO was only slightly reduced by these compounds. It is concluded that AMPH enhances ACH release through increased NO synthesis and induces neurotoxicity via NO and by LPO independent NO generation.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

CIRCADIAN rhythmicity in mammals, is controlled by the suprachiasmatic nuclei (SCN) of the hypothalamus. We previously described a discrete subnucleus in the core of the hamster SCN containing calbindin-D28k-positive cells which are fos-positive in response to a light pulse. Ablation of this subnucleus results in loss of circadian locomotor rhythmicity even when other parts of the SCN are spared. Here we show that Tau mutant hamsters have significantly more calbindin-D28kin the SCN than do wild type hamsters, and that SCN calbindin-immunoreactivity in the SCN increases in the dark. This is correlated with changes in magnitude of light mediated phase shifts in locomotion. The data are consistent with a role for calbindin cells in light mediated entrainment and phase shifting.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

IT is well established that the mammalian circadian system consists of pacemaker cells in the suprachiasmatic nuclei (SCN). The mouse has become increasingly important in understanding the circadian timing system, due to the availability of mutant animals with abnormal circadian rhythms. In the present paper, we describe the organization of the mouse SCN, comparing the wild type and Clock mutant animal, with a special focus on those peptides bearing an upstream E-box element (vasopressin, vasoactive intestinal peptide, cholecystokinin and substance P). To this end, we describe the distribution of the foregoing SCN peptidergic cell types as well as gastrin-related peptide, calretinin, calbindin, somatostatin, neurotensin and retinal input to the SCN (determined by both tract tracing and fos-immunoreactivity in response to a light pulse). The Clock mutant mouse has decreased expression of vasopressin mRNA and protein in the SCN, with normal patterns of expression elsewhere in the brain. No other differences were detected between the Clock mutant and the wild type mouse. The results are consistent with the hypothesis that there are multiple regulatory elements of clock-controlled genes in the SCN.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

THE effect of visual contrast on sentence reading was investigated using event-related brain potentials (ERPs). Under the low contrast condition semantic integration as reflected in the N400 ERP component was delayed to some degree. The left anterior negativity (LAN) reflecting initial syntactic processes, in contrast, seemed to change its characteristics as a function of visual input. In the high contrast condition the LAN preceded the P200 component whereas in the low contrast condition it was present after this component. These ERP-data from word-by-word sentence reading together with prior results from sentence listening suggest that the physical characteristics of the input must fall within a certain optimal range to guarantee ERP-effects of fast initial syntactic processes.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

DOPAMINE is co-localized with 5-hydroxytryptamine in a ventromedially located plexus in the lamprey spinal cord and reduces Ca2+currents in motoneurons that express high-voltage activated Ca2+currents of the N-, L- and P/Q-types. Blockade of L- and P/Q- type channels leaving N-type channels intact reduced but did not prevent the inhibition of the Ca2+current by dopamine. Dopamine also reduced the L-type current potentiated by BAY K 8644. During simultaneous blockade of N-type and L-type currents, dopamine was unable to affect the remaining Ca2+current. In addition, blockade of G-proteins abolished the dopaminergic modulation. The inhibition was unaffected by depolarizing prepulses. Thus, dopamine mediates inhibition of N- and L-type currents through a G-protein-dependent, voltage-independent pathway in lamprey spinal motoneurons.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID