摘要:

AbstractSix cynomolgus monkeys (Macaca fascicularis) were trained to associate visual stimuli with the delivery of various amounts of food reward. The animals had to choose correctly between pairs of stimuli drawn from a population of 16. Four of these stimuli were associated with 0 reward pellets, four with 1 pellet, four with 2 pellets and four with 4 pellets. Mediodorsal thalamic lesions including the medial part of the mediodorsal nucleus, similar to those which are frequently seen in Korsakoff amnesia, produced a severe impairment in this task. The impairment was seen both in memory for the quantity of reward, as expressed in choices between 1‐pellet and 2‐pellet stimuli or choices between 2‐pellet and 4‐pellet stimuli, and also in memory for the qualitative absence or presence of reward, as expressed in choices between 0‐pellet and 1‐pellet stimuli. The deficit in this task establishes that mediodorsal thalamic lesions in monkeys can impair long‐term memory tasks, in addition to their known effects on several short‐term memory tasks. The contrast between the present results and those of previous experiments on visual long‐term memory in the monkey following mediodorsal thalamic lesions can be related to similar contrasts in studies of lesions in the amygdala, suggesting that the functions of these two struc

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00847.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIntracellular recordings were made from rat abducens motoneuronsin vivoduring local extracellular micro‐ionophoretic application ofN‐methyl‐d‐aspartate (NMDA) and NMDA receptor antagonists. Typical NMDA responses, at a resting potential of –60 mV, consisted of a slow depolarization with an apparent increase in membrane resistance, bursts of action potentials followed by stable repetitive firing, lonophoretic applications of aminophosphonovalerate (APV), kynurenate or MK801 reduced or blocked the NMDA‐induced responses. The NMDA responses were voltage‐dependent. NMDA responses induced by short (30 s) NMDA applications induced rhythmic plateau potentials in hyperpolarized abducens motoneurons. The rhythmic depolarizations (15–30 mV) were modulated in both frequency and duration by current injection. They were abolished by further hyperpolarization or replaced by stable repetitive firing when hyperpolarization was removed. Our data show that NMDA receptors are present in rat abducens motoneurons and may be involved in the induction of rhythmic activities. The voltage‐dependent blockade of somatic NMDA receptor‐associated ion channels by cell hyperpolarization may be important for these oscillations. It is suggested that the rhythmic behaviour is due to the activation of dendr

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00848.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe two neural cell adhesion molecules L1 and N‐CAM could be shown to be associated in the surface membrane of cultured neuroblastoma cells by chemical cross‐linking with 3,3′‐dithiobis(sulphosuccinimidylpropionate) and subsequent immunopurification and precipitation using antibodies to L1 and N‐CAM. Glycoproteins recognized in neuroblastoma cells by antibodies to mouse liver membranes were not chemically cross‐linked to L1 or N‐CAM. These observations suggest that a molecular association between the two molecules may be the basis for their functional cooperativity (Kadmonet al., 1990a, b, J. Cell Biol., 110, 193

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00849.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe innervation of dendrites of identified entorhinal principal cells by fibres originating in the nucleus reuniens thalami was studied in the rat. The lectinPhaseolus vulgaris‐leucoagglutinin (PHA‐L, anterograde tracer) was injected into the nucleus reuniens and the fluorescent dye Fast Blue (retrograde tracer) into the hippocampus. After survival, perfusion‐fixation and the preparation of brain slices, entorhinal neurons retrogradely labelled with Fast Blue were intracellularly injected with the dye Lucifer yellow to introduce a specific marker into their dendrites. The transported PHA‐L and the injected Lucifer yellow were visualized through dual peroxidase immunohistochemistry. Varicosities on PHA‐L labelled reuniens fibres abut ascending and descending Lucifer yellow‐filled secondary dendrites of multipolar and pyramidal principal entorhinal neurons that possess either spiny or sparsely spiny dendrites, but they do not appose the perikarya of these cells. In the electron microscope, PHA‐L labelled boutons in the entorhinal cortex were observed forming asymmetrical synaptic contacts with dendritic spines (50%) or shafts (50%). The results indicate that direct thalamic input occurs on dendrites of neurons in the entorhinal cortex which project to th

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00850.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThis study investigates the role of the pontine grey as a link between the auditory system and the cerebellum in the bat,Rhinolophus rouxi.We recorded response properties of single neurons in the pontine grey and, in the same preparation, injected wheat germ agglutinin ‐ horseradish peroxidase (WGA‐HRP) in areas responsive to sound. Thus the functional evidence was correlated with retrograde and anterograde transport. The main results are: (i) all auditory neurons in the pontine grey are tuned within one of two harmonically related frequency ranges of the echolocation call. The upper range corresponds to the constant frequency and frequency modulated components of the second harmonic, but the lower range corresponds only to the frequency modulated component of the first harmonic. There is no systematic tonotopic organization; (ii) discharge patterns are extremely variable, latencies cover a wide range, and about half of the neurons are binaurally responsive with excitation from both ears; (iii) most pontine auditory neurons respond preferentially to frequency modulated stimuli; (iv) there is massive input to the pontine grey from the central nucleus of the inferior colliculus; (v) cortical input to the pontine grey does not originate in tonotopically organized auditory cortex. The input is from a dorsal belt area that is specialized for processing combinations of sounds with specific frequency ratios and delays; (vi) projections from the auditory region of the pontine grey are widespread within the cerebellar cortex. The data suggest that the pontine grey transmits to the cerebellum information contained in specific components of the bat's biosonar sig

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00851.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractNeurite outgrowth from cells of neuroepithelial origin is under the reciprocal control of thrombin and the thrombin inhibitor‐glia‐derived nexin (GDN). The neurite retraction activity of thrombin is blocked when GDN complexes with the enzyme and inhibits its proteolytic activity. However, we have previously shown that enzymically inactive proenzyme is also capable of inducing neurite retraction. We present evidence here to show that GDN does not bind to prothrombin in solution. When a mixture of prothrombin and GDN is subjected to either polyacrylamide gel electrophoresis or immunoprecipitation, a stable complex cannot be detected. This is in direct contrast to thrombin, which exhibits stable complexes with GDN under both conditions. At the cell surface, however, GDN is able to inhibit the biological activity of prothrombin. When a mixture of proenzyme and inhibitor is applied to previously differentiated transformed retinobiasts (Ad12 HER10), the ability of prothrombin to induce neurite retraction is blocked. Furthermore, following 1 h exposure to Ad12 HER10 cells, a solution of prothrombin was found to contain half the potential enzyme activity as detected by chromogenic assay. These results have been interpreted as evidence for the ability of neuronal cells to cleave prothrombin and subsequently release activated enz

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00852.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA class of putative synaptic terminals with concentrated cAMP binding sites are labelled in unfixed sections of rat brain by means of the ligand 8‐thioacetamido fluorescein cAMP (SAF‐cAMP), a fluorescent analogue of cAMP. The labelled terminals appear as sharply delimited bouton‐like structures in close proximity but external to the cell body of neurons. The SAF‐cAMP binding, measured at equilibrium in competition with other nucleotides, indicates that the binding site recognizes the cAMP moiety of SAF‐cAMP. In the labelled terminals of the frontal cortex the concentration of SAF‐cAMP binding sites is estimated to be in the millimolar range (at least 2.1 ± 1.0 mM). In a brain homogenate, labelled terminals are visualized only in the membrane fraction enriched in synaptosomes. The cAMP binding activity of the synaptosomes is insoluble in high and in low ionic strength solution and is only partially solubilized by detergents, suggesting that the binding sites are intrinsic membrane proteins and/or proteins associated with the cytoskeleton. There is the possibility that SAF‐cAMP labels new cAMP binding sites highly concentrated in a class of synaptic terminals. SAF‐cAMP labelling is prominent in well defined regions of the rat brain: (i) the frontal and entorhinal areas of the cortex; (ii) the field CA1 of the hippocampus; (iii) the olfactory system; (iv) the medial nuclei of the thalamus; (v) the parabrachial nuclei and other less defined regions of the reticular substance; (vi) the substantia gelatinosa of Rolando in the spinal cord; and (vii) the neo‐ and paleocerebellum in the Purkinje cell layer, the archicerebellum in the granular cell layer. SAF‐cAMP labelling is absent in specific motor and sensory structures, with the exception of the olfactory system. It is proposed that SAF‐cAMP binding sites single out a new type of synaptic terminals involved in com

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00853.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractBrain‐derived neurotrophic factor (BDNF) is a member of a family of related neurotrophic proteins which includes nerve growth factor (NGF) and hippocampus‐derived neurotrophic factor/neurotrophin‐3 (NT‐3). To obtain information regarding possible roles for BDNF during postnatal brain development, we have examined the temporal and spatial expression of this trophic factor usingin situhybridization. In specific neocortical regions BDNF mRNA‐expressing cells were seen at 2 weeks of age and thereafter. One particular neuronal cell type strikingly labelled was the inverted pyramidal cell population in the deep layers of parietotemporal cortex. In pyriform and cingulate cortices, BDNF mRNA was detected at postnatal day 1 and 1 week of age, respectively, with increasing levels during ontogeny. Several forebrain regions, including the thalamic anterior paraventricular nucleus, hypothalamic ventromedial nucleus as well as the preoptic area, contained moderate levels of BDNF mRNA throughout development. BDNF mRNA was detected transiently in several brainstem structures, notably in the substantia nigra and interpeduncular nucleus. Expression of this trophic factor in hippocampus was relatively low in the early neonatal brain, but attained high levels in the CA3 and CA4 regions as well as in the dentate gyrus by 2 weeks of age. At this early age, which is still during the period of neurogenesis in the dentate gyrus, labelling was restricted to the outer layer, which contained cells with a more mature appearance. However, by 3 weeks of age labelling was distributed throughout the granule cell layer. Our results show both transient and persistent expression of BDNF mRNA in various regions of the developing rat brain and suggest that there is a caudal to rostral gradient of BDNF expression during postnatal brain development, which may be correlated to neuronal m

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00854.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractNerve growth factor (NGF) induces transient Fos‐immunoreactivity (Fos‐IR) independently of any other factor, both in newly isolated rat sympathetic neurons and in established cultures after NGF deprivation. The same proportion of neurons that express Fos‐IR in response to NGF also survive. In addition to direct stimulation of Fos‐IR expression, the presence or recent exposure to NGF is required to obtain Fos‐IR expression by other stimuli. In newly isolated neurons no Fos‐IR is detected in response to stimulation by serum alone and a response to depolarization or cyclic AMP is obtained only if neurons are stimulated within a short period after ganglion excision. In established cultures none of these stimuli, nor the trauma of cutting neurites or spiking cell bodies with a microinjection needle induce Fos‐IR unless NGF is present or had been removed for<8–16 h. The lack of response is not due to a general decrease in the rate of protein or RNA synthesis. These findings show that in regenerating sympathetic neurons NGF induces c‐Fos and suggest that NGF may activate a master trigger that is required for c‐Fos expression to be induc

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00855.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe action of calcitonin gene‐related pepide (CGRP) was studied on c‐fos gene expression in rat astrocyte cultures. A strong and transient increase in c‐fos mRNA was observed in cultured astrocytes after treatment with CGRP. Quantitative Northern blot analysis revealed an increase of c‐fos mRNA within 15 min, a peak after 30 min with a 10–15 fold increase over unstimulated cells and a subsequent decline. Induction of the c‐fos gene by CGRP was concentration‐dependent, half maximal stimulation of c‐fos mRNA being obtained with 100 nM CGRP. The CGRP effect appeared to be mediated by a CGRP receptor and calcitonin was found to mimic only weakly the action of CGRP on cultured astrocytes. Calcitonin transiently induced c‐fos gene expression with a similar time course to CGRP, but its effect was much less pronounced. Agents affecting the intracellular cyclic AMP level, forskolin and Ro 20–1724, stimulated c‐fos mRNA in a strong and transient fashion with a temporal sequence similar to the response to CGRP. Further, the phosphodiesterase inhibitor Ro 20–1724 potentiated the action of CGRP on c‐fos mRNA induction, suggesting a role for cyclic AMP in the action of CGRP. The present results indicate that CGRP may play a physiological role as a regulator of

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1991.tb00856.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY