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  • 1
    Electronic Resource
    Electronic Resource
    The role of the anterior intralaminar nuclei and N-methyl D-aspartate receptors in the generation of spontaneous bursts in rat neocortical neurones (1986)
    Springer
    Experimental brain research 63 (1986), S. 505-518 
    Details
    ISSN: 1432-1106
    Keywords: Intralaminar nuclei ; Neocortex ; Somatosensory ; NMDA ; 2APV ; Thalamo-cortical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The nature of spontaneous unitary activity of rat neocortex was investigated during slow wave sleep and urethane anaesthesia. Neurones in layer IV and V locations fired in a burst-pause pattern at a low burst repetition rate (0.5–4 per second) during both stage 3/4 sleep and urethane anaesthesia. Occasionally an alternative mode of firing (spindle clusters), associated with focal spindle wave activity, was also found to occur in both states. Using dual microelectrode implants it was found that the onset times of bursts (but not spindle clusters), coincided in the same and opposing cortices, whether in functionally similar or disparate areas. The highest probability was that burst onsets occurred simultaneously (resolution =2.56 ms, interquartile range=40 ms). Spontaneous unitary activity was investigated in the thalamus for temporal correlation with spontaneous unitary activity in neocortex under urethane anaesthesia. Neurones of the anterior intralaminar group (aIL) consistently fired in a burst-pause pattern such that each aIL burst showed a strong tendency to precede a cortical burst. Unilateral electrical stimulation of the aIL nuclei evoked widespread bilateral entrainment of cortical bursts. In contrast stimulation of VP1, or cutaneous sites, evoked only short duration spike responses together with burst abolition in the appropriate restricted Sm1 area. Ionophoresis of NMDA (N-Methyl D-Aspartate) onto Sm1 neurones increased the probability of cortical burst responses to aIL stimulation in addition to decreasing the latency by 20–40 ms (n=11). lonophoresis of 2APV (2-amino 5-phosphono valeric acid) caused simultaneous abolition of spontaneous cortical bursts and bursts evoked by aIL stimulation. Short latency responses to cutaneous and VP1 stimulation were unaffected by ionophoresis of 2APV sufficient to cause burst elimination, suggesting that this pathway does not operate via a 2APV sensitive receptor mechanism. Anatomical features of the aIL nuclei and their overall cortical projection pattern are discussed in relationship to these findings. The activation of cortical NMDA/APV sensitive receptors by aIL afferents in the “spontaneous” generation of bursts in cortical cells is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237474
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  • 2
    Electronic Resource
    Electronic Resource
    Bilateral receptive fields of cells in rat Sm1 cortex (1988)
    Springer
    Experimental brain research 70 (1988), S. 155-165 
    Details
    ISSN: 1432-1106
    Keywords: Sm1 cortex ; Receptive fields ; Rat ; Bilateral receptive fields ; Hindlimb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Single cells in the primary somatosensory (Sm1) cortex were investigated for responses to bilateral hindpaw stimulation in Wistar rats anaesthetised by continuous intravenous administration of Althesin. Fifty-one percent of cells sampled (N = 134) responded to equivalent punctate mechanical stimuli delivered to both the contralateral and ipsilateral hindpaws under light anaesthesia. The distribution by cortical depth of cells with receptive fields (RFs) on both hindpaws was not significantly different from cells which had only contralateral RFs. No cell was found with a purely ipsilateral RF. For 86% of cells tested (N=44) the ipsilateral RF was partly or completely homologous with areas within the contralateral RF. The sizes of ipsilateral RFs were smaller on 66% of occasions when tested against their contralateral RFs. Modal latencies to ipsilateral mechanical stimulation were longer than to contralateral stimulation (34.1±9.1 ms (S.D) cf. 26.4±7.2 ms, N=44). Ipsilateral RFs were lost for 77% of cells tested following a 33% increase in anaesthetic infusion rate. Conditioning mechanical stimuli applied to the centre receptive field (CRF) on the ipsilateral hindpaw reduced or abolished a cell's responses to equivalent test stimuli applied to it's contralateral CRF with C-T intervals of 20–200 ms. Conditioning stimuli applied to the CRF contralateral to the cell reduced or abolished responses to test stimuli on the cell's ipsilateral CRF using C-T intervals of 0–900 ms. Responses in one cortex to stimulation of the ipsilateral hindpaw were unaffected by elimination of responses from the same hindpaw in the opposite contralateral Sm1 cortex, where responses had been suppressed by topical Lignocaine administration. Retrograde transport of horseradish peroxidase from hindpaw Sm1 cortex labelled many cells in homolateral thalamus, but failed to label cells in the entire forebrain contralateral to the injection site. It is concluded that direct crossed thalamocortical and callosal Sm1-Sm1 pathways do not contribute to the production of hindpaw ipsilateral receptive fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271857
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Threshold effects of N-methyl D-aspartate (NMDA) and 2-amino 5-phosphono valeric acid (2APV) on the spontaneous activity of neocortical single neurones in the urethane anaesthetised rat (1985)
    Springer
    Experimental brain research 60 (1985), S. 209-213 
    Details
    ISSN: 1432-1106
    Keywords: Neocortex ; NMDA ; 2APV ; Somatosensory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Spontaneous activity of single neurones in neocortex was sampled using pairs of microelectrodes in rats anaesthetised with urethane. In confirmation of previous studies, many cells recorded from middle layers characteristically fired in bursts, the onset times of which were synchronous both unilaterally and bilaterally. Iontophoresis of 2APV onto such cells either caused an abolition of bursts or a reduction in spikes per burst. In the latter case action potentials which occurred later in the burst were preferentially abolished. Iontophoresis of NMDA onto the same cells caused a prolongation of bursts with minimal effect on intraburst interspike interval. In interactive trials with the two drugs the effect of NMDA could be abolished by 2APV, and NMDA counteracted the effect of 2APV. It is concluded that spontaneous burst generation in neocortex during urethane anaesthesia is generated through a cortical NMDA/2APV-sensitive receptor mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237036
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of thiamine deficiency on the structure and physiology of the rat forebrain (1988)
    Springer
    Metabolic brain disease 3 (1988), S. 91-124 
    Details
    ISSN: 1573-7365
    Keywords: thiamine deficiency ; thalamic intralaminar nuclei ; neocortex ; synchronous burst spontaneous activity ; excitotoxic brain lesions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Dietary thiamine deficiency, enhanced by pyrithiamine administration in adult rats, produces overt lesions in the brain that are especially prominent in the thalamus. The present study was undertaken to determine whether the thalamic lesions could be correlated with alterations in the physiological properties of neurons in the thalamus and somatosensory cortex. The regimen for experimentally inducing thiamine deficiency produced large lesions in the thalamus of every case; the lesions included most, if not all, of the neurons in the intralaminar thalamic nuclei. The extent of the lesion in the intralaminar thalamus was highly correlated with the loss of bilaterally synchronous spontaneous activity in the cerebral cortex. This correlation was seen in animals analyzed as early as 1–18 hr after the appearance of opisthotonus, the crisis state of thiamine deficiency, and as late as 2–9 weeks of recovery following thiamine replacement therapy. The loss of bilateral synchronous bursting neuronal activity following intralaminar thalamic lesions is consistent with the proposed role of the intralaminar thalamus as a pacemaker for rhythmic cortical activity (Armstrong-Jameset al.,Exp. Brain Res., 1985; Fox and Armstrong-James,Exp. Brain Res. 63: 505–518, 1986). The location and size of the central lesions within the thalamus suggest that the observed neuronal loss could result from a nonhemorrhagic infarction in the ventromedial branches of the superior cerebellar arteries. Experimental thiamine deficiency also produced alterations in the receptive field properties of the somatosensory cortex neurons in all animals examined. Changes in cortical receptive field properties were correlated with the destruction of sensory relay neurons in the thalamic ventrobasal complex. The loss of the central lateral thalamic input to the cortex and the loss of somatosensory relay neurons in the ventrobasal thalamus in experimental thiamine deficiency produce alterations in cortical function which may contribute to deficits in memory and cognition analogous to those which characterize Korsakoff's psychosis in humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01001012
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    Paper (German National Licenses)
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