摘要:

AbstractThis study of somatosensory discrimination of rectangular parallelepipeds with the right hand had three purposes: (i) to describe the exploratory finger movements; (ii) to reveal the anatomical brain structures specifically engaged in the production of exploratory finger movements; and (iii) to reveal the anatomical structures specifically engaged in the discrimination of tactually sensed shape. The thumb was the most active finger, moving with a mean exploration frequency of 2.4 Hz, as evident from videotape records of the exploratory finger movements. The cerebral structures activated during somatosensory discrimination were mapped by measurements of regional cerebral blood flow (rCBF) in six healthy male volunteers with positron emission tomography (PET) and the use of the computerized brain atlas of Greitzet al.(1991,J. Comp. Ass. Tomogr., 15, 26–38). The rCBF changes caused by somatosensory discrimination were compared point‐to‐point to a PET‐study on right‐hand finger movements and a PET‐study on vibration stimulation of the right hand. From these results the following conclusions were drawn. The rCBF increase in the left superior parietal lobule indicated the site engaged in the analysis of shape. The rCBF increases in the left supplementary sensory area, bilaterally in premotor areas, in the left putamen, the right dentate nucleus and bilaterally in the posterior cerebellum were related to the control of the tactile exploratory finger movements. The rCBF increases in the right homologue of Broca's area, bilaterally in the superior prefrontal cortex and in the right midfrontal cortex probably resulted from working memory, the direction of attention, and the discriminat

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00835.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractNumerous anatomical and electrophysiological studies have demonstrated a lack of simple point‐to‐point topographical relationships between the olfactory bulb and primary olfactory projection areas. They reveal instead, a complex pattern of divergence and convergence. Furthermore, several authors reported that a single mitral cell could project onto different widely spaced cortical regions of the olfactory cortex. In the present study, we attempted to label the projections of a few mitral cells so close together so that they might be assumed to be connected to the same glomerulus, and to determine if these cells had similar patterns of axonal projections. For this purpose smallPhaseolus vulgarisleucoagglutinin (PHA‐L) injections were performed in the olfactory bulb of adult rats. We found that labelling two to five mitral cells, lying close together in the mitral cell layer, resulted in well‐delineated patches of labelled fibres in the cortex. The number of patches was not related to the number of labelled mitral cells but the fibre density in each patch increased with the number of PHA‐L filled somata in the olfactory bulb. We conclude that mitral cells lying close together in the mitral cell layer have similar patterns of axonal projections. Functional implications of such an organization in olfactory coding is

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00836.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe ultrastructural relationships between γ‐aminobutyric acid‐immunoreactive (GABA‐ir) neurons and other neurons of the nucleus tractus solitarius (NTS) and motoneurons of the nucleus ambiguus (NA) and dorsal motor vagal nucleus (DMVN), were examined by electron microscopic (EM) immunogold labelling with an anti‐GABA antiserum on brain stem sections in which vagal motoneurons and vagal afferent fibres were labelled with horseradish peroxidase (HRP). HRP was applied to the cervical vagus or the cardiac vagal branch of anaesthetized cats. After 24–48 h survival, brains were glutaraldehyde‐fixed and a stable HRP‐tetramethylbenzidine reaction product compatible with EM processing was revealed on 250 μm vibratome sections. Following osmium postfixation, dehydration and resin embedding, GABA‐ir was localized on ultrathin sections by an immunogold technique. GABA‐ir axon terminals, heavily and specifically labelled with gold particles, were very numerous within NTS, DMVN and NA. All terminals contained small, clear, pleomorphic vesicles and a few also contained larger dense cored vesicles. The density of gold particles over clear vesicles, dense cored vesicles and mitochondria was significantly greater than over the cytoplasm of these terminals. GABA‐ir synapses were found on the soma and dendrites of neurons, but rarely on other axon terminals within NTS, where GABA‐ir cell bodies and dendrites were also seen. These received synaptic contacts from both GABA‐ir terminals and from HRP‐labelled vagal afferents. In both the DMVN and NA, similar GABA‐ir synapses were present on both the soma and dendrites of HRP‐labelled motoneurons. GABA synapses were also present on other cell types in DMVN. These observations provide an anatomical basis for a GABAergic inhibition of neurons forming the central pathways of cardiovascul

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00837.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIn the presence of retinoic acid, cultured human neuroblastoma SH‐SY5Y cells grow processes indicative of neuronal differentiation. A voltage‐gated Ca current is already present in undifferentiated cells. A gradual increase of the Ca current density occurs during cell differentiation. According to kinetic and pharmacological properties, Ca currents in differentiated cells are indistinguishable from those elicitable in undifferentiated cells and resemble features of the high‐voltage activated currents present in mammalian neuronal cells. ω‐conotoxin strongly depresses high‐voltage activated currents, both in undifferentiated and in differentiated SH‐SY5Y cells. Interestingly, the Ca agonist Bay K 8644 is effective, albeit with great variability from cell to cell, only in differentiated cells and only when barium is the current carrier through the Ca channels. A diversity of high‐voltage activated Ca channels of distinct pharmacology has been recently observed in other kinds of neurons. This requires a redefinition of the role that voltage‐dependent Ca channel subtypes can play in m

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00838.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractMast cell degranulating peptide (MCDP) is a neurotoxic agent isolated from bee venom. It produces a long‐term potentiation in the hippocampus. We now report that MCDP, at nanomolar concentrations, induces a reduction of a transient voltage‐dependent potassium current (ID) in CA3 rat pyramidal neurons and a persistent (>30 min) enhancement of the frequency of spontaneous miniature excitatory and inhibitory postsynaptic currents (m.e.p.s.c.s. and m.i.p.s.c.s.). M.e.p.s.c.s. and m.i.p.s.c.s. were recorded in the presence of bicuculline (30 μM) and 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX, 10 μM), respectively. The increased frequency of m.e.p.s.c.s. (408±60%) and m.i.p.s.c.s. (583±553%) was independent of the reduction of IDbecause 4‐aminopyridine (4‐AP, 30 μM‐2 mM) blocked IDbut had no effects on m.e.p.s.c.s. and m.i.p.s.c.s. In the presence of the calcium channel blocker manganese (3 mM), MCDP still enhanced the frequency of m.e.p.s.c.s. (326±162%). It is concluded that MCDP augments the release of excitatory and inhibitory transmitter by an action, which is independent of calcium influx, through v

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00839.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe effects of intraventricular and intracortical microinjections of acidic amino acid antagonists on self‐stimulation (SS) of the medial prefrontal cortex (MPC) were investigated. Self‐stimulation was measured by depressing a lever in a standard chamber. Spontaneous motor activity of the animal and SS of the contralateral non‐injected MPC were used as control for non‐specific effects of the drugs. Intraventricular microinjections of γ‐d‐glutamylglycine (DGG), an antagonist of NMDA, kainate and quisqualate receptors, or 2‐amino‐5‐phosphonovalerate (AP‐5), a specific antagonist of NMDA receptors, produced a dose‐related decrease of SS in the MPC. Spontaneous motor activity of the animal was not significantly affected. Unilateral microinjections into the medial prefrontal cortex of DGG or AP‐5 produced a decrease of SS in the ipsilateral side while no effects were found on the contralateral MPC. On the contrary, intraventricular microinjections of γ‐d‐glutamyltaurine (Glu‐tau), an antagonist with more relative affinity for kainate and quisqualate receptors, produced a dose‐related decrease of both self‐stimulation and spontaneous motor activity of the rats. Moreover, intracortical microinjections of Glu‐tau had no effect on self‐stimulation of this cortical area. These results suggest that acidic amino acids through NMDA, but not kainate or quisqualate, receptors could be part of the neurochemical substr

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00840.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractAdenosine has a broad array of actions on neurons but astrocytes also possess adenosine receptors. We have previously shown that adenosine, by acting on astrocytes in the striatum, can modulate neuronal responses mediated by receptors coupled to phospholipase C through an astrocyto‐neuronal interaction. In addition, adenosine was found to potentiate the α1‐adrenergic production of inositol phosphates in astrocytes. The mechanism involved in this potentiation was further investigated by examining the effects of adenosine and α1‐adrenergic receptor agonists on cytosolic Ca2+in cultured striatal astrocytes from the embryonic mouse in primary culture. When used alone, methoxamine, a selective agonist of α‐adrenergic receptors or 2‐chloroadenosine, a stable analogue of adenosine, induced a transitory increase in cytosolic Ca2+, but their combined addition led to a sustained increase in cytosolic Ca2+, which seems to be due to a Ca2+influx, because it was not observed in the absence of external Ca2+. Voltage independent Ca2+channels contribute to this process and different blockers of voltage‐operated calcium channels, such as dihydropyridines, phenylalkylamines, La3+or Co2+were ineffective in suppressing the sustained cytosolic Ca2+elevation. Three observations suggest the implication of arachidonic acid in the observed potentiation: (i) arachidonic acid induced a sustained elevation of cytosolic Ca2+similar to that evoked by the coapplication of methoxamine and 2‐chloroadenosine; (ii) the addition of arachidonic acid during the calcic plateau produced by the combined application of the agonists did not increase further cytosolic Ca2+levels; (iii) in the presence of methoxamine, 2‐chloroadenosine induced a release of arachidonic acid. The stimulation of phospholipase C and the resulting activation of protein kinase C induced by methoxamine seem to be required for the potentiating effect of 2‐chloroadenosine on cytosolic Ca2+. In fact, the direct activation of protein kinase C by an exogenous diacylglycerol analogue mimicked the effect of methoxamine because, in this condition, 2‐chloroadenosine alone evoked a sustained elevation of cytosolic Ca2+. Therefore, methoxamine, through the successive activation of phospholipase C and protein kinase C, could allow a lipase, probably phospholipase A2, to be stimulated by 2‐chloroadenosine. Arachidonic acid has already been shown to trigger the opening of K+channels and the formation of inositol phosphates in other cell types. Therefore, in striatal astrocytes, 2‐chloroadenosine, through an arachidonic acid‐mediated hyperpolarization, could increase the Ca2+driving force and thus improve Ca2+influx through inositol phosphate‐gated channels. This hypothesis is further supported by the suppressing effect of a 50 mM KCI‐induced depolarization on the long lasting elevation of cytosolic Ca2+seen in the combined presence of 2

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00841.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe state of neuronal microtubule polymerization is influenced by microtubule‐associated proteins such as MAP2, which is specifically localized within neuronal dendrites and cell bodies. We have demonstrated that stimulation of spinal cord or cortical neuronsin vitrowith excitatory amino acids results in a dramatic modification of the neuronal cytoskeleton as monitored with antibodies against MAP2 and tubulin. Stimulation of cultures with glutamate receptor agonists induced a reorganization of MAP2 immunoreactivity into a distinctive network of bundles within certain neuronal cell bodies and their proximal neurites. The effect was not abolished by depolymerizing drugs such as nocodazole, or protein synthesis inhibitors. The effect was dependent upon the entry of sodium following depolarization and was not associated with neuronal damage. We suggest that in neurons the state of the neuronal cytoskeleton can be modulated by glutamate receptor activation acting through MAP

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00842.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractChick embryo retinas were labelledin ovoby single injections of [3H]thymidine at selected times between days 2 and 12 of incubation. Embryos were later removed, at different stages of development, and the retinas processed for autoradiography of either serial sections or dissociated cell preparations. Analysis of unlabelled cells shows that neurogenesis starts, on day 2 of incubation, in a dorsotemporal area of the central retina, close to the posterior pole and to the optic nerve head. A gradient of neurogenesis spreads from this central area to the periphery, where neurogenesis ends, shortly after day 12, when the last few bipolar cells withdraw from the cell cycle. Additional dorsal‐to‐ventral and temporal‐to‐nasal gradients can be discerned in our autoradiographs. In all retinal sectors, ganglion cells start first to withdraw from the cell cycle, followed, with substantial overlapping, by amacrine, horizontal, photoreceptor plus Müller, and bipolar neuroblasts. Ganglion cells are also the first to reach the 50% level of unlabelled cells, followed this time by horizontal, photoreceptor, amacrine, Müller and bipolar cells. Finally, 100% levels of unlabelled cell populations are attained simultaneously by ganglion, horizontal and photoreceptor cells, followed by amacrine, then by Müller, and last by bipolar cells. Although all classes of neurons, in varying proportions, are being produced most of the time, our results also demonstrate that, in any given retinal area, the first cells leaving the cycle are determined to become ganglion cells, and the last ones bipolar cells, and not o

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00843.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractVoltage‐sensitive dyes and fast optical recording techniques were used to monitor the spatio‐temporal activity pattern of epileptiform potentials in hippocampal slices from guinea pigs. Epileptiform potentials were induced by adding 4‐aminopyridine to the bath solution and applying single pulse stimulation either to the stratum pyramidale of area CA3 or to the stratum radiatum of area CA1. Optical activity as well as intra‐ or extracellular electrical activity were recorded from area CA1. There was a good correlation between optical and intracellular records from the same site. The spatio‐temporal activity pattern of control and epileptiform potentials elicited by stimulation of CA1 was similar for the initial part of the potential. Then, epileptiform changes became apparent throughout the vertical extent of pyramidal neurons. Qualitative changes occurred in the stratum moleculare, reflecting activity of apical dendrites, such changes occurred even more strongly in the stratum oriens, reflecting activity of basal dendrites. The activity in the stratum oriens occurred relatively late, so that it cannot account for the initiation of epileptic discharges. It might, however, play an important role in the synchronization and spread of epileptiform potentials. The investigation of the horizontal distribution of potentials throughout the entire area CA1 indicates that different mechanisms are involved in the spread of epileptiform activity elicited by stimulation of CA1 and stimulati

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00844.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY