摘要:

CHOLINE acetyltransferase (ChAT) and the vesicular acetylcholine transporter (VAChT) are both encoded by the cholinergic gene locus which, is the rat, five different species of ChAT mRNA and three different species of VAChT mRNA are produced. So far, discrimination between mRNA subtypes has been possible only in CNS homogenates or in cell cultures. In this study, cardiac neurons were microdissected from frozen sections of rat heart using a u.v. laser and harvested using a micromanipulator. RT-PCR demonstrated the expression of the non-coding R-exon and splicing to R1-type mRNA in the majority of cardiac neurons. The technique presented here is first to allow subtype analysis of cholinergic locus mRNA species in neuronsin situ.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE ability to use fMRI in a monkey model would bridge the gap between the fMRI demonstration of cerebral activation in humans and the cumulative wealth of monkey data on the functional organization of the brain from single electrode mapping, radioisotope and histology studies. We report a new technique for fMRI in an awake co-operative rhesus macaque (Macaca mulatta) in a conventional clinical 1.5T MR scanner and present the first fMRI images from a macaque. Good resolution, signal-to-noise ratio and BOLD response (2.6–4.6%) have been achieved using the manufacturer's standard volume knee coil. T1 values of macaque gray and white matter (1490 ms, 1010 ms respectively) are higher than human brain, whereas T2 values are lower (55 ms, 48 ms respectively). An MR-compatible design for restraining the monkey is also described, along with a suitable EPI sequence for BOLD images, optimized for monkey T2, with voxel sizes from 29 to 61 μl, and MPRAGE sequence for anatomical studies with 0.8 mm isotropic resolution, optimized for monkey T1.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE editing status of mRNA at the Q/R site of the glutamate receptor subunits GluR2 and GluR6 modulates channel conductivity and ion selectivity of ionotropic AMPA/KA receptors. Alteration of the editing process may be involved in the debilitating effects of epilepsy. The ratio of unedited/edited (Q/R) forms of GluR2 and GluR6 subunits was examined in conjunction with the expression of two double-standard RNA-specific adenosine deaminases (DRADA) in surgically excised hippocampus from patients with refractory epilepsy compared with that of control samples. In the majority of patients with long histories of epilepsy, the GluR2 transcript was detected in the completely edited form, however, in two (out of 16 tested) hippocampal samples of young subjects (2 and 10 years old) we were able to identify the unedited transcript of GluR2 subunit. The proportion of unedited fraction of GluR6(Q) subunit was decreased to 9% compared to control human hippocampus. We conclude that the editing process in epileptic specimens is selectively affected by seizure activity in the epileptic focus.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IMPAIRED auditory feedback has been suggested to cause stuttering, and subtle irregularities of audition have been reported in behavioural studies. To characterize processing at the auditory cortical level, we recorded neuromagnetic responses to monaural tones in nine stutterers and 10 fluent speakers while the subjects were reading silently, with mouth movements only, aloud, and in chorus with another person. The basic functional organization of the auditory cortices was found to be different in stutterers and controls. The altered inter-hemispheric balance in stutterers was affected by speech production, due to changes in the left auditory cortical representation, and more severely by self-paced than accompanied speech. This may lead to transient non-optimal interpretation of the auditory input and affect speech fluency.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Neuronal nitric oxide synthase (nNOS), an enzyme that synthesizes NO, has been found in the outer retina using light microscopic immunocytochemistry, but its subcellular localization is unknown. We used electron immunocytochemistry to examine nNOS-like immunoreactivity (nNOS-LI) in the outer plexiform layer of turtle and rat retinas. In turtle, nNOS-LI was present in some bipolar and horizontal cell processes at photoreceptor ribbon synapses and at basal junctions between photoreceptors. In rat, nNOS-LI was present in some rod bipolar and B-type horizontal cell axon terminals at rod ribbon synapses. These results indicate that in vertebrates, NO is produced by all of the major nerve cell types in the outer retina at specific synaptic contacts.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

LONG-TERM depression was established in cerebellar Purkinje cells using 20 pairings of a brief, high frequency train of parallel fiber stimulation with a subsequent 100 ms depolrizing current injection. Effects were assessed on the peak amplitude of Purkinje cell excitatory post synaptic potentials (EPSPs) elicited by single parallel fiber test pulses. Intradendritically recorded Purkinje cell EPSPs exhibited long-term (> 20 min) reduction in peak amplitude following paired stimulation but not if pretreated with the protein kinase C inhibitor calphostin C or iontophoretically injected with the calcium chelator EGTA. The similarity of the stimulation protocol and behavioral conditioning paradigms suggests pairing-specific long-term synaptic depression is a valuable model for understanding the cellular mechanisms underlying cerebellar cortical contributions to learning.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE recently isolated peptide nociceptin has a primary structure similar to that of opioid peptides. Early functional studies suggested that it may act in opposition to opioid systems. To determine whether nociceptin influences the rewarding properties of heroin, nociceptin was given intracerebroventricularly (i.c.v.) to rats trained to self-administer heroin. Rats (n= 8) were given doeses of 0.01 μg, 0.1 μg 1.0 μg and 10.0 μg in a Latin square design. None of the doses significantly affected heroin self-administration rates compared to vehicle. The highest dose of nociceptin used inhibited spontaneous locomotor activity, evidence that the peptide retained its biological activity after i.c.v. infusion. These studies suggest that nociceptin does not affect the rewarding value of heroin.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

DYSTROPHIN immunocytochemistry was carried out using monoclonal antibody against the C-terminal part of dystrophin (Dys2) in rat cerebral cortex, cerebellum and hippocampus containing a high number of spine synapses of similar morphological character. Dys2 immunoreactivity was found in the spine component of spine synapses. Particularly heavy label was observed on the postsynaptic densities. In the cerebral and cerebellar cortices all spines were immunopositive. In the hippocampus some postsynaptic densities were intensely immunostained, whereas those of adjacent synapses remained unstained. The findings suggest that dystrophin is an integral protein of the postsynaptic component of spine synapses but is lacking in a subpopulation of hippocampal spine synapses. The heterogeneity of input to the hippocampal spiny sites by contrast to the homogeneous population of fibres synapsing with cerebral and cerebellar cortical spines is suggested to account for differences.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

SINCE motion sickness (MS) never occurs in individuals who lack functional vestibular apparatus, it has been suggested that MS susceptible individuals have more sensitive vestibular systems that non-susceptible people. However, previous investigations involving only stimulation of the semi-circular canals have been inconclusive. We measured gain and time constant (TC) of horizontal canal–ocular reflex (COR) and magnitude of otolith–ocular reflex (OOR). We found that MS susceptibility was not correlated to COR gain but was negatively correlated to OOR magnitude. Thus, MS susceptible individuals do not have more sensitive vestibular systems. We also found a positive correlation between MS susceptibility and TC. We hypothesize that central vestibular integration (velocity storage mechanism), by increasing low frequency vestibular inputs, would favour MS.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

DIRECT currents (DC) applied directly to central nervous system structures produce substantial and long-lasting effects in animal experiments. We tested the functional effects of very weak scalp DC (< 0.5 mA, 7 s) on the human motor cortex by assessing the changes in motor potentials evoked by transcranial magnetic brain stimulation. We performed four different experiments in 15 healthy volunteers. Our findings led to the conclusion that such weak (< 0.5 mA) anodal scalp DC, alternated with a cathodal DC, significantly depresses the excitability of the human motor cortex, providing evidence that a small electric field crosses the skull and influences the brain. A possible mechanism of action of scalp DC is the hyperpolarization of the superficial excitatory interneurones in the human motor cortex.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID