摘要:

AbstractMonoclonal antibody subplate‐l (mAb SP1) specifically stains somata, dendrites and axons of spiny inverted pyramidal neurons in the subplate zone in the early postnatal kitten neocortex. The SP1 antigen has been previously identified as a cytosolic protein of apparent molecular weight 56 kDa. We have now employed immune‐affinity chromatography to further characterize this antigen. An antigen with SP1‐like immunoreactivity (ir) is present in various organs, and is particularly enriched in blood plasma. Exsanguination of the organs prior to protein extraction reduces the SP1‐ir band dramatically, indicative of a blood‐borne molecule. The 56 kDa SP1‐ir antigen was purified from plasma by affinity chromatography and subjected to Edman degradation. The first 20 N‐terminal amino acids show 80% homology to the N‐terminus of immunoglobulin heavy chain of man, the mouse and the dog. If the 56 kDa SP1‐ir antigen in plasma is an immunoglobulin, and if an immunoglobulin‐like molecule is present in the subplate, then antisera against cat immunoglobulins should stain subplate neurons. A polyclonal antiserum against cat IgG intensely stains the somata and dendrites of subplate neurons. On protein blots, this antiserum recognizes the 56 kDa band, and an additional band of ∼27 kDa, corresponding in size to immunoglobulin light chains. Preabsorbing mAb SP1 with cat immunoglobulin G abolishes the immunoreactivity in sections of kitten cortex. Further, it dramatically reduces the reactivity on protein blots. The results suggest that the 56 kDa SP1‐ir antigen in cortical subplate neurons belongs to the imm

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00313.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractExcitation of afferent fibres originating in the ventral subiculum of the hippocampus through stimulation of the fimbria elicits field potentials in the nucleus accumbens. When recorded in the dorsomedial aspect of the nucleus accumbens, the evoked field responses consisted of an early, negative‐going component (Nl) with a peak latency of 8–10 ms, followed by a second negative‐going peak (N2) with a latency of 22–24 ms. The N1 response reflects monosynaptic activation of nucleus accumbens neurons; the N2 component appears to be polysynaptic in origin. In control rats, high‐frequency stimulation of the fimbria (three trains at 250 Hz, 250 ms, delivered at 50 min intervals) resulted in a long‐lasting potentiation of both the N1 and N2 components. The magnitude of potentiation exhibited by the polysynaptic N2 response was typically greater than that of the monosynaptically evoked N1 response. Following delivery of the first train, the amplitude of the N1 and N2 components was increased by ‐20 and 50% respectively. Administration of the competitiveN‐methyl‐d‐aspartate (NMDA) receptor antagonist 3‐[(±)‐2‐carboxypiperazin‐4‐yl]‐propyl‐1‐phosphonic acid (CPP, 10 mg/kg i.p.) had no significant effects on the evoked nucleus accumbens responses. High‐frequency stimulation failed to produce a significant increase in the amplitude of either the N1 or the N2 response when delivered 45–60 min after CPP administration. To test whether the suppressant effects of CPP were time‐dependent, two further high‐frequency trains were applied 90 and 180 min after administration of the drug. Significant increases in the amplitude of the N1 and N2 components were observed only after the third train, delivered 180 min after CPP injection. These results demonstrate that high‐frequency stimulation of hippocampal afferents to the nucleus accumbens induces LTP in both a monosynaptic and a polysynaptic pathway. In both cases, the induction of LTP is suppressed in a time‐dependent manner by the competitive NMDA receptor antagonist CPP. Thus, NMDA receptor activation appears to be prerequisite for the inducti

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00314.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe nucleus accumbens in the rat has been parcelled into shell and core subdivisions. Despite accumulating evidence for such a division of the nucleus accumbens, these territories have not been delineated throughout the rostrocaudal extent of the nucleus. In the present study, an attempt has been made to delineate the shell and core using the distribution of calcium‐binding protein immunoreactivity, substance P immunoreactivity and acetylcholinesterase activity in transverse and horizontal sections through the nucleus accumbens. It was found that the pattern of calcium‐binding protein immunoreactivity provides the most unequivocal criterion to divide the nucleus accumbens into a ventral and medial, peripheral shell displaying low to moderate immunostaining, and a more laterally and dorsally located, strongly stained inner core. In most parts of the nucleus, borders seen in the calcium‐binding protein immunoreactivity pattern can also be recognized in the distributions of substance P immunoreactivity and acetylcholinesterase activity. It is concluded that the shell occupies most of the rostral part of the nucleus accurnbens, whereas rostrally the core is represented only in the most lateral part. Differences in staining intensities for all three markers indicate that both the shell and core have a heterogeneous structure. Patterns of connectivity appear to support the division of the nucleus accumbens as indicated by calcium‐binding protein immunoreactivity in the presen

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00315.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThis study examined the effects of ibotenate lesions of the entorhinal cortex (EC) on performance of a spatial recognition memory task, the delayed non‐matching‐to‐place task (DNMTP), varying in level of difficulty according to the number of interpolated arm visits between sample‐place presentation and subsequent recognition in mice. Results of experiment 1, designed to test the rate of acquisition of the task, showed that experimental animals were impaired in the basic non‐matching task. However, with further training they were able to learn the task. Impairments were also observed when the amount of interpolating information inserted was gradually increased, and then all problem difficulties were pseudorandomly tested. There was no measurable recovery of function over time when the animals were retested on the task ∼1 month later. Experiment 2 showed that the animals that received extensive training on the task prior to lesions of the EC were only transiently impaired in the DNMTP task. These data suggest that the EC plays an important role in acquisition rather than retention of the spatial recognition

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00316.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractMore than 90% of dorsal horn neurons from embryonic day 15–16 rats responded to the inhibitory amino acids GABA and glycine by a transient elevation of intracellular Ca2+concentration ([Ca2+]i) when maintained in culture for<1 week. This [Ca2+]iresponse has previously been shown to be due to depolarization and subsequent Ca2+entry through voltage‐gated Ca2+channels following activation of bicuculline‐sensitive GABAAreceptors and strychnine‐sensitive glycine receptors. Both the number of cells responding to GABA and glycine and the amplitude of the [Ca2+]iresponse diminished over time in culture. By 30 days in culture, none of the cells responded to GABA, muscimol or glycine by elevation of [Ca2+]i. The loss of the [Ca2+]iresponse was not due to a change in the abundance or the properties of voltage‐gated Ca2+channels, since over the same period of time dorsal horn neurons showed a large increase in the amplitude of the [Ca2+]itransient in response to 30 mM K+. Nor was the loss of the [Ca2+]iresponse due to a loss of GABA and glycine receptors. Instead, the decrease in the [Ca2+]iresponse over time paralleled a similar change in the electrophysiological responses. More than 90% of the neurons tested were depolarized in response to inhibitory amino acids during the first week in culture. After 30 days, all neurons tested responded to GABA and glycine with a hyperpolarization. These observations add support to the suggestion that GABA and glycine may excite dorsal horn neurons earlyin development and play a role in postmitotic differ

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00317.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractTwo chick optic lobe α‐bungarotoxin receptor subtypes (α7 and α7 ‐ α8) were immunopurified using polyclonal antibodies raised against synthetic peptides of chick α7 and α8 α‐bungarotoxin receptor subunits. The α7 subtype contained theMr57 000 α7 subunit, and represented 60 ‐ 70% of the α‐bungarotoxin receptors; the α7‐α8 subtype contained theMr57 000 α7 and α8 subunits, and represented only 20 ‐ 25% of the receptors. Both subtypes also had an additionalMr52 000 subunit. The affinity of these subtypes for α‐bungarotoxin as well as antagonists was similar. However, the α7 ‐ α8 subtype displayed consistently higher affinities for agonists. When reconstituted in planar lipid bilayers, the α7 ‐ α8 subtype displayed several conductance states of 10 ‐ 50 pS; the α7 subtype had only one conductance state of 45 pS. The α7 ‐α8 subtype was activated by lower agonist concentrations than the α7 subtype. When expressed inXenopusoocytes, the α8 subunit formed functional homomeric receptors that desensitized rapidly. These channels were blocked by α‐bungarotoxin and displayed a higher affinity for agonists than the α7 homomeric receptor. Taken together, these data indicate that at least two α‐bungarotoxin subtypes are present in the chick optic lobe. They operate as ligand‐gated channels and display different a

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00318.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractGlucocorticoids can modulate behavioural processes and neural plasticity. They are released during learning situations and can trigger neural actions through binding to brain receptors. We hypothesized that a glucocorticoid action could play a critical role in the mechanisms involved in long‐term memory formation. In order to test this hypothesis, chicks were trained on a passive avoidance learning task and given bilateral intracerebral injections of selective mineralocorticoid (RU‐28318) or glucocorticoid (RU‐38486) receptor antagonists. The results showed that both antagonists alter information processing when injected prior to the training session. Possible state‐dependent effects were discharged. Further experiments evaluating possible effects of the antagonists on concomitant aspects of the learning situation (such as novelty reaction and pecking pattern) indicated that, as opposed to the glucocorticoid receptor antagonist, the mineralocorticoid antagonist altered the birds' reactivity to non‐specific aspects of the training task. These results suggest that the two types of intracellular corticosteroid receptors could be mediating different aspects of the information processing and storage involved in avoidance learning. In addition, this study points out that passive avoidance learning in the chick could be a good model to investigate the biochemical mechanisms involved in corticosteroid actions on learning‐induced neura

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00319.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractCat eye movements were recorded during wakefulness and paradoxical sleep with the technique of the scleral search coil in a magnetic field. During waking, eye movements consisted of a succession of saccades and fixation phases. During paradoxical sleep, the pattern of eye movements displayed drifts of variable velocity and direction and short fixation phases, upon which saccades superimposed. These saccades displayed a repetitive, stereotyped, asymmetrical pattern. The maximum velocity/amplitude relationships, i.e. the main sequences, were determined for spontaneous and visually induced saccades of waking and for the following types of saccades during paradoxical sleep: (i) isolated saccades accompanied by ponto‐geniculo‐occipital (PGO) waves, (ii) isolated saccades accompanied by eye movement potentials (EMP), and (iii) saccades in bursts accompanied by PGO waves. The slope of the main sequence relationship of any type of paradoxical sleep saccade (from 21.7°/° for isolated saccades to 35.6°/s° for saccades in bursts) was higher than that of any type of waking saccade (11.2°/s° for spontaneous saccades to 14.7°/s° for visually elicited ones). Furthermore, during paradoxical sleep, saccades in bursts were faster than isolated ones. This demonstrates that different neurophysiological mechanisms subserve the generation of waking saccades, paradoxical sleep isolated saccades and paradoxical sleep saccades in bursts, or that the oculomotor system is in a different state of excitation during these different sets of saccades. These findings throw new light on the functioning of the oculomotor system during paradoxical sleep and are discussed in terms of the functional significance of paradoxical sleep saccades an

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00320.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThis study investigated the potential of immature and adult serotonin (5HT) neurons for axonal growth into intrastriatal grafts of ventral mesencephalic tissue. Implantation of dissociated fetal (embryonic days 14–15) ventral mesencephalic tissue was carried out in immature [postnatal days (P) 5–14] and adult rat neostriatum. The brains were processed 2–6 months later for dopamine and 5‐HT immunocytochemistry. A few grafts implanted into adult and P7 recipients contained small numbers of cotransplanted 5HT cell bodies. These also displayed a rich network of 5‐HT axons, even in adult rats prelesioned with 5,7‐dihydroxytryptamine, indicating the graft origin of these axons. All other grafts were totally devoid of 5‐HT cell bodies. After implantation in adults, such grafts contained rare 5‐HT axons. In contrast, in P5‐P7 recipients, they displayed many 5‐HT fibres, which were uniformly distributed. Such was no longer the case after implantation in P14 recipients, which showed minimal 5HT innervation, as in adult recipients. Processing of naïve rat brain at different ages for 5‐HT immunocytochemistry showed that 5‐HT axons were still clearly less numerous in the neostriatum at P21 than in adults, whereas in the substantia nigra the 5‐HT innervation developed more rapidly and was comparable, at P21, to that of adults. It was concluded that 5‐HT axons are able to grow into ventral mesencephalic grafts, but mainly at the fetal stage and with decreasing capacity after birth. Since 5‐HT axons are still normally growing in the developing striatum beyond P21, it appears that their inability to innervate mesencephalic grafts after P14 is not the result of a developmental decrease in growth capacity. Rather, the better temporal correlation with the maturation of the 5‐HT innervation in the substantia nigra suggests that this inability reflects an ontogenic change in the affinity

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00321.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractSuperior cervical ganglion neurons from neonatal rats are dependent on nerve growth factor for their survival bothin vivoandin vitro.In culture this requirement can be largely replaced by cAMP or its analogues. Since activation of protein kinase A by cAMP is likely to be the pathway by which it exerts its survival‐promoting effect, we have tested the feasibility of using herpes simplex virus (HSV) as a vector for expressing survival‐promoting genes in neurons by cloning the catalytic subunit of the CAMP‐dependent protein kinase (PKAcat) with a metallothionein gene promoter into the HSV thymidine kinase gene by homologous recombination. About 95% of the neurons became infected using 2.5 p.f.u. per cell. When this construct was used to express PKAcat in superior cervical ganglion neurons, in the presence of nerve growth factor (NGF) increases of 1.9‐ to 2.4‐fold in PKA activity were found 8–10 h after infection; levels remained elevated (1.4‐ to 2.1‐fold) up to 18 h, returning to basal by 24 h. After infection in the absence of NGF, cumulative activity over 24 h was ∼3.5‐fold lower in the first 24 h. Although the level of the inhibitory regulatory subunit type I was raised by 18 h, this is unlikely to completely explain the transient activity of PKAcat. When neurons were induced to express maximum PKAcat levels in the presence of NGF and then deprived of NGF, survival was extended by up to 2 days, demonstrating a direct role for PKA in promoting survival. By this time, some neurite degeneration was beginning which appeared to be partly due to toxic effects of the virus. However, replenishment with NGF supported further survival, showing that at this time the neurons were still viable. Similar rates of survival were obtained using a tsK‐based PKAcat vector, but no significant survival was obtained with parental HSV or tsK virus strains. These data demonstrate the feasibility, and highlight some of the problems, of using HSV‐based vectors as tools for expressing functional survival proteins

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00322.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY