摘要:

AbstractSimultaneous recording of complex spikes from multiple Purkinje cells (up to 44) in the rat cerebellum was used to examine the effects of 5‐hydroxytryptamine (serotonin, 5‐HT) on olivocerebellar function. Microinjection into the inferior olive was found to increase the average firing rate of inferior olivary neurons while slowing their oscillation frequency and increasing the coherence of their oscillations. Indeed, while the normal rostrocaudal band of synchronous activity remained unchanged, the degree of synchrony between Purkinje cell complex spikes within this band was enhanced following the 5‐HT injections. Multiple‐electrode recordings obtained from crus Ha and vermal lobule Vlb yielded qualitatively similar results; however, the effects on vermal activity were more pronounced. The effects of the 5‐HT microinjection decayed with a time course of 75 min. The half‐maximum effective concentration of 5‐HT was between 10 and 100 μM. Injections of various 5‐HT agonists and antagonists demonstrated that a 5‐HT type‐2A (5‐HT2A) receptor is the main mediator for the 5‐HT effect, which was very similar to the effect produced by injections of harmaline. However, 5‐HT and harmaline appear to have independent mechanisms since the action of harmaline was not blocked by the 5‐HT2Aantagonist LY53857. A possible role for 5‐HT, as a physiological enhancer of the timing of motor function of the olivoc

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00657.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractPolyclonal and monoclonal antibodies prepared against the α‐subunit of the voltage‐gated sodium channel (αNaCh) were used to examine the distribution of sodium channel‐like immunoreactivity during the prenatal development of the cat and rhesus monkey (Macaca mulatta) retina. At all prenatal ages studied, beginning on embryonic day 29 (E29) in the cat and E52 in the monkey, both antibodies labelled optic axons. With the polyclonal antibodies, the appearance of positive cells largely mirrored the onset of their morphological maturation. Immunoreactivity appeared first in the somata of ganglion cells, and subsequently the inner plexiform layer could be distinguished by its intense immunolabelling. A few weeks later horizontal cells displayed immunolabelling that extended to their dendrites in the developing outer plexiform layer. This was followed by immunoreactive cones, with bipolar cells labelled only postnatally. By contrast, with the monoclonal antibody some cells were found to be immunoreactive while their somata were still in the ventricular layer (E33 in cat and E52 in monkey). Many of these cells appeared to migrate to the outer portion of the prospective inner nuclear layer, where they gradually acquired the morphological appearance of bipolar cells. Transient expression of immunolabelling with monoclonal sodium channel antibody was found in the cones of the cat and cones and rods of the monkey. These results indicate that different types of αNaCh‐like proteins are expressed in the mammalian retina at distinct developmental periods. Their presence at very early stages during development suggests that these proteins could play a specific role in the commitment and/or differentiation of specific retinal

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00658.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractNeurocan is a developmentally regulated chondroitin sulphate proteoglycan in the rat brain. In the present study, spatiotemporal patterns of expression of neurocan and the corresponding mRNA were examined in the developing cortical barrel field of the rat brain by using a monoclonal antibody that was highly specific to neurocan and a riboprobe for a portion of the mRNA. Immunohistochemical analysis revealed that neurocan was distributed throughout the cerebral cortex during early postnatal development but was excluded from the centres of cortical barrels at the time of entry and arborization of thalamocortical axons. At this developmental stage, expression of neurocan mRNA was shown by in situ hybridization to be down‐regulated in the barrel centres. When a row of whisker follicles was laser‐cauterized on postnatal day 1, the pattern of expression of neurocan was disturbed in the row of barrels that corresponded to the lesioned whisker follicles in the contralateral somatosensory cortex. From these observations, it appears that neuronal stimuli through early thalamocortical fibres from the sensory periphery cause reduced expression of neurocan mRNA in neurocan‐producing cells in the presumptive barrel centres. Our findings also suggest that the pattern of distribution of neurocan in early postnatal barrel fields may be due mainly to the down‐regulation of expression of neuroc

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00659.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA number of studies have indicated a possible interaction between dopamine and the vestibular system. Using intracellular recordings in brainstem slices, we have tested the effects of dopamine and other dopaminergic compounds on guinea‐pig medial vestibular nucleus (MVN) neurons. In normal medium, MVN neurons were depolarized by dopamine as well as by (‐)quinpirole and piribedil, which are selective D2dopaminergic agonists. The dependence of this effect on the presence of D2receptors was confirmed by using (‐)sulpiride, a D2antagonist which blocked the depolarizing effect of dopamine. Dopaminergic D1receptors were apparently not involved in this effect since a selective D1agonist, SKF‐38393, had no effect on MVN neurons and the D1antagonist (+) SCH‐23390 could not block the effect of dopamine. These depolarizing responses to dopamine must be due to a presynaptic action on terminals that normally release GABA spontaneously on MVN neurons, and tonically maintain them in a state of hyperpolarization. Indeed, such a spontaneous release was demonstrated to occur in the slice since application of bicuculline, a GABAAantagonist, depolarized MVNneurons in normal saline, but not in a high Mg2+/low Ca2+solution known to block synaptic transmission. When dopamine was applied in conditions in which no GABAA‐dependent transmission could occur (either in the presence of bicuculline or in a high Mg2+/low Ca2+solution) only a hyperpolarizing, most probably postsynaptic, effect occurred. These results indicate that dopamine might exert in vivo a significant modulatory action on the vestibular system, either by a direct action on the vestibular neurons or by modulation of GABAergic t

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00660.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractTraining chicks on a one‐trial passive avoidance task results in transient up‐regulation of theN‐methyl‐d‐aspartate (NMDA) receptor in the left intermediate medial hyperstriatum ventrale (IMHV) of the forebrain 30 min post‐training. Injection of the non‐competitive NMDA receptor inhibitor, (+)‐5‐methyl‐10, 11‐dihydro‐5H‐dibenzo‐ (a.d)‐cyclohepten 5, 10‐imine maleate (MK‐801), around the time of training renders chicks amnesic for the task. Training also results in enhanced expression of the immediate early gene (IEG) c‐fosin the IMHV. To determine the relationship between NMDA receptor up‐regulation and IEG induction during memory formation we have examined the expression of Fos, Jun and their related proteins 1 h following training in the presence/absence of the putative amnestic agent MK‐801. Western blotting of IMHV samples revealed two protein bands with immunoreactivity to the Fos antibody at 47 and 54 kDa. Using an antibody to Jun, two immunoreactive bands were revealed at 39 and 54 kDa. All bands were enhanced in the left IMHV following passive avoidance training. Post‐training intraperitoneal injections of MK‐801 (75 mM) produced amnesia in ∼50% of the birds when tested 1 h after training. Injection of MK‐801 significantly attenuated expression of these proteins in birds rendered amnesic, but not in those that recalled the task. We conclude that NMDA receptor activation precedes immediate early

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00661.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe extent and functional subdivisions of the auditory cortex in the echolocating horseshoe bat,Rhinolophus rouxi, were neurophysiologically investigated and compared to neuroarchitectural boundaries and projection fields from connectional investigations. The primary auditory field shows clear tonotopic organization with best frequencies increasing in the caudorostral direction. The frequencies near the bat's resting frequency are largely over‐represented, occupying six to 12 times more neural space per kHz than in the lower frequency range. Adjacent to the rostral high‐frequency portion of the primary cortical field, a second tonotopically organized field extends dorsally with decreasing best frequencies. Because of the reversed tonotopic gradient and the consistent responses of the neurons, the field is comparable to the anterior auditory field in other mammals. A third tonotopic trend for medium and low best frequencies is found dorsal to the caudal primary field. This area is considered to correspond to the dorsoposterior field in other mammals. Cortical neurons had different response properties and often preferences for distinct stimulus types. Narrowly tuned neurons (Q10dB<20) were found in the rostral portion of the primary field, the anterior auditory field and in the posterior dorsal field. Neurons with double‐peaked tuning curves were absent in the primary area, but occurred throughout the dorsal fields. Vocalization elicited most effectively neurons in the anterior auditory field. Exclusive response to pure tones was found in neurons of the rostral dorsal field. Neurons preferring sinusoidal frequency modulations were located in the primary field and the anterior and posterior dorsal fields adjacent to the primary area. Linear frequency modulations optimally activated only neurons of the dorsal part of the dorsal field. Noise‐selective neurons were found in the dorsal fields bordering the primary area and the extreme caudal edge of the primary field. The data provide a survey of the functional organization of the horseshoe bat's auditory cortex in real coordinates with the support of cytoarchitectural boundaries and connection

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00662.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSimultaneous microdialysis in the brain and blood was used to monitor the release of vasopressin and oxytocin within the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei and into the systemic circulation of urethane‐anaesthetized male rats before and after central administration of interleukin‐1β (IL‐1β). Following intracerebroventricular infusion of the cytokine (200 ng/5 μl), the content of vasopressin (up to 278% compared to vehicle‐treated control, P<0.01 compared to vehicle‐treated control and preinfusion baseline) but not oxytocin (up to 148%, not significant) in 30‐min blood microdialysates was found to be increased. This peripheral release was accompanied by a transient rise in vasopressin (up to 163%, P<0.05) and oxytocin (up to 182%, P<0.05) release within the SON, the peak typically occurring during the first and second 30‐min collection intervals after IL‐1 β respectively. In contrast, in the simultaneously microdialysed PVN, both vasopressin and oxytocin failed to respond to intracerebroventricular IL‐1 β. In another series of experiments, IL‐1 β was directly infused (20 ng0.5 μl) into either the SON or PVN during microdialysis of the corresponding nucleus. The cytokine caused a significant and immediate rise in intra‐SON release of both vasopressin (up to 225%, P<0.01) and oxytocin (up to 178%, P<0.05). Again, in the PVN, nonapeptide release, although tending to be stimulated in response to intranuclear IL‐1 β, failed to reach statistical significance. The cytokine‐induced central and peripheral release pattern appeared to be independent of the rise in body temperature observed after IL‐1 β administration. In a third series of experiments, bilateral administration of IL‐1 β into the SON (20 ng/0.5 μl) failed to alter peripheral release of both vasopressin and oxytocin into the systemic circulation. The increase in central nonapeptide release in response to IL‐1 β shown in this paper supports the hypothesis that at least vasopressin might act to oppose central effects of the cytokine, including those on thermoregulation and behaviour, in this way contributing to the ne

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00663.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this study, the formation of the corticotectal projection of the rat in organotypic slice culture was investigated, using both anatomical and physiological approaches. The establishment of fibre connections from visual cortex to superior colliculus explants was monitored after 3, 6, 14, 20 and 30 daysin vitroby cortical injections of Dil. As in cortical cultures without cocultured colliculus, fibres anterogradely labelled by this procedure spread radially from the injection site into the surroundings of the explant, without displaying any directional preference. Especially, layer V pyramidal cells could be seen to extend processes not only to the collicular target, but also in the opposite direction, suggesting that no axonal guidance was exerted by the projection target. The total number of fibres projecting in the direction of the colliculus was not higher than of those projecting in the opposite direction. However, fibres projecting into the colliculus were significantly longer. This was also the case when the colliculus was placed next to the pial side of the cortical explant, indicating that outgrowth direction was not related to this observation. We therefore assume a chemotrophic rather than a chemotactic influence of the projection target on cortical axons, which is based on direct contact of axons to the target tissue. It cannot be excluded, however, that the failure to detect chemotactic guidance was caused by the lack of diffusion gradients in our culture system. Innervation of the collicular slice exclusively originated from layer V pyramidal cells, irrespective of the position of the collicular target. Fibre courses suggested that discrimination of the projection target was achieved upon encounter with the collicular surface by direct membrane contact. Inside the collicular tissue, fibre arborizations occurred preferredly in up to three layers perpendicular to the surface. Even after the smallest tracer injections, termination fields were diffusely distributed over the collicular slice. Also, the spatial distribution of retrogradely stained projection neurons did not differ statistically from an equal distribution. Thus, a high degree of convergence and divergence was observed anatomically in the corticotectal projection formedin vitro, corresponding to the immature statein vivo.The functionality of the corticotectal projection was assessed by intracellular recordings from collicular neurons. Electrophysiological properties, such as membrane potential (‐68 ± 11 mV), membrane resistance (35.4 ± 27.7 Mω) and the time constant (3.0 ± 2.1 ms) were comparable to reference values, confirming the viability of our culture preparation. The functionality of corticotectal transmission was revealed by intracellularly recorded responses of collicular cells to extracellular cortical stimulation. Most responses were excitatory (90%), although inhibitory responses were also encountered (10%). High‐frequency stimulation suggested polysynaptic transmission in all cases tested. Responses from single collicular cells could always be elicited from various cortical stimulation sites, which were usually distributed over the whole cortical explant, confirming the high degree of convergence suggested by the anatomical results. Conduction velocities of corticotectal fibres were estimated to be ∼0.3 m/s, indicating that the fibres of the corticotectal connectionin vitrowere probably unm

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00664.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe addition of chondroitin sulphate proteoglycans (CSPGs), purified from the rat brain, to the culture medium of PC12D cells inhibited their proliferation and neurite outgrowth. Therefore, we investigated the effects of several extracellular components on the inhibitory actions of CSPGs on PC12D cells, as well as their immunocytochemical distribution in the rat embryo to determine whether the findingsin vitrocould be reproducedin vivo.Coating of the substratum with polylysine was necessary for the appearance of the inhibitory effects of brain CSPGs on PC12D cells. The additional pretreatment of polylysine‐coated dishes with laminin or fibronectin promoted the outgrowth of neurites from PC12D cells. Laminin and fibronectin, but not collagen (types I and IV) and CELL‐TAK (cell adhesion molecules), prevented the inhibitory effects of brain CSPGs in a concentration‐dependent manner. Doses producing 50% reduction by laminin (or fibronectin) of the CSPG effects were 1.5 (or 25) μg/ml for neurite outgrowth and 2.2 (or 28) μg/ml for proliferation. The ratio of dish‐attached CSPGs to laminin necessary for 50% reduction was about ∼50:l (wt/wt). Laminin from any source had the same effect. Brain CSPGs also obviously impeded the growth of fibres from dorsal root ganglion explants and primary cultured dorsal root ganglion neurons. Neurocan (a major CSPG in the brain)‐like immunoreactivity was detected in the boundary caps and roof plate in the rat embryo at 13.5 days of gestation, when DRG neurons were extending their axons to the neural tube. The distributions of laminin and tenascin appeared, respectively, to be slightly and considerably different from that of neurocan. These results suggest that brain CSPGs can generate barriers to the growth of axons from the dorsal root ganglion and that the ratio of CSPGs to laminin may be important in regulatin

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00665.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA cDNA encoding the human metabotropic glutamate receptor type 2 (hmGluR2) was isolated from human brain cDNA libraries by cross‐hybridization with rat mGluR2 probes. The deduced amino acid sequence of the human mGluR2 receptor consists of 872 residues and shows a sequence identity of 97% to the amino acid sequence of rat mGluR2. Northern blot analyses showed that hmGluR2 is widely expressed in different regions of the adult brain as well as in fetal human brain. Genomic Southern blotting localized the mGluR2 gene to human chromosome 3. Chinese hamster ovary (CHO) cells stably transfected with the cloned hmGluR2 cDNA exhibit agonist induced depression of forskolin‐stimulated cAMP accumulation. A direct comparison of CHO cells stably expressing human and rat mGluR2 with five agonists revealed the same rank order of potency [(2S,3S,4S)‐α‐(carboxycyclopropyl)‐glycine » (1S,3R)‐1‐aminocyclopentane‐1,3‐dicarboxylic acid =l‐glutamate » quisqualate =l‐2‐amino‐4‐phosphonobutyric acid] and similar EC50values for both homologous receptors. (R.S)‐a‐methyl‐4‐carboxyphenylglycine, a reported antagonist at some mGluR subtypes, reduced the depression of forskolin‐induced cAMP accumulation by (

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1995.tb00666.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY