摘要:

AbstractIn immobilized decerebrate cats fictive locomotion was evoked by midbrain stimulation to analyse the efferent pattern to elbow and to distal forelimb muscles innervated by the deep radial nerve. The locomotor activity was assessed by recording nerve discharges and motoneuronal membrane potential changes. The elbow flexor and extensor motoneurons showed a reciprocal activity; the membranes were correspondingly depolarized and hyperpolarized. In the motor nuclei to the wrist and digit extensors the active phases changed systematically according to the radio‐ulnar order of the muscles: the extensor carpi radialis (ECR) was flexor‐coupled, the ulnaris (ECU) extensor‐coupled, the digitorum communis (EDC), the lateralis (EDL) and the indicis proprius (EIP) displayed intermediate patterns. Intracellular recordings from these motoneurons revealed in all motor nuclei, except ECR, a double depolarization. The first occurred early and the second later in the flexor phase; a hyperpolarization was interposed. The second depolarization mainly determined the active phase. According to the radio‐ulnar order of the muscles the onset and termination of the second depolarization were delayed. This was presumably due to the interposed hyperpolarization, which progressively increased in amplitude. The ECR exhibited a single depolarization, into which the double depolarization apparently merged. The other radial motor nuclei, supinator (Sup) and Abductor pollicis longus (APL) displayed complex patterns. Sup showed tonic discharges, flexor‐type discharges or discharges extending both into the flexor and extensor phase, APL showed discharges similar to either EIP or Sup. Membrane potential changes were small in APL and Sup. Thus, the central locomotor network generates differentiated efferent activities in the distal forelimb muscles, the radio‐ulnar order of the muscles being important for the genera

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00456.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractDual labelling methods were applied to localize simultaneously neuropeptide Y (NPY) and glutamate decarboxylase (GAD) immunoreactivities on ultrathin sections of the rat caudate‐putamen (CP). By means of a double peroxidase‐anti‐peroxidase technique, using 3,3′‐diaminobenzidine and benzidine dihydrochloride as chromogens in animals with no colchicine pretreatment, GAD immunoreactivity was found to be present in terminals only whereas NPY immunoreactivity was detected in neurons displaying the features of aspiny type cells and processes. With this approach, we observed numerous synaptic associations of the symmetrical type between GAD‐immunoreactive (‐Ir) axonal boutons and NPY‐Ir cell bodies and dendrites. By combining immunoperoxidase and radioimmunocytochemical labelling in animals pretreated with colchicine, NPY was again detected in a single population of aspiny type neurons whereas GAD immunoreactivity was observed in neurons which could be classified as aspiny and spiny on the basis of their ultrastructural characteristics. All the cells of the aspiny type displaying clear‐cut NPY immunoreactivity were also found to be GAD‐positive. Some other neurons of both the aspiny and the spiny type were found to be immunoreactive to GAD alone. GAD/NPY dually labelled terminals were also observed and some axo‐axonic appositions between GAD‐ and NPY‐Ir terminals were also detected. All in all, these data show that NPY aspiny type neurons of the rat CP receive GABAergic afferents and provide morphological support for two hypotheses: that NPY is co‐localized with GABA in some cell bodies, dendrites and axons, and that presynaptic interactions may occur between NPY and

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00457.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn the normal guinea pig a map of auditory space appears, in the deeper layers of the superior colliculus, at 32 days after birth (DAB). The animal is unable to construct this collicular map of auditory space in the absence of developmental visual experience. Auditory receptive fields of animals dark‐reared from birth are typically large, occupying most of the contralateral hemifield. There is no topographic relationship between the collicular location of the recording electrode and the spatial position from which auditory stimuli elicit a maximal response. The fields of dark‐reared animals resemble, in their tuning parameters, the spatially undifferentiated fields typical of young postnatal normal guinea pigs. To investigate the time‐course during which visual experience is required for map emergence, animals received normal visual experience until either 18 or 26 DAB and were then dark‐reared until the terminal mapping experiment. Maps developed in neither group. Animals provided with a normal visual environment until 30 DAB, and then placed in the dark did, however, construct topographically organized spatial maps with discrete spatial receptive fields. Maps also failed to emerge in animals receiving normal visual experience both before and after a 4‐day period of visual deprivation between 26 and 30 DAB. We conclude that this 4‐day period, or part of it, constitutes a ‘crucial’ period during which visual experience is required for the normal elaboration of the collicular map of

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00458.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractGuinea pigs, reared from birth in an environment of omnidirectional white noise, fail to develop a map of auditory space in the deeper layers of the superior colliculus. Collicular responses from such noise‐reared animals reveal large auditory spatial receptive fields. The representation of auditory space in the colliculus shows no topographic order. Exposing developing animals to the noise environment only for restricted time periods showed that animals reared normally up to 26 days after birth (DAB) and then placed in the noise chamber could not construct spatial maps, whereas animals reared normally to 30 DAB and then placed in the noise chamber until the terminal mapping experiment could construct topographically organized spatial maps with local receptive fields. Limiting the noise exposure to the period between 26 and 30 DAB was sufficient to prevent spatial map formation. The failure to form a map of auditory space did not reflect environmental damage to the cochlea or the functional organization of the primary auditory pathway. The response thresholds of cochlear microphonics and of auditory responses in both the inferior and superior colliculus were normal in noise‐reared animals. Similarly normal were the tonotopic organization and frequency tuning characteristics of inferior collicular neurons. The rearing environment thus appears to exert a selective effect upon the maturation of the superior collicular map of auditory space. We attribute this effect to the masking, by the omnidirectional broad‐band noise, of discrete localized auditory stimuli. Cues deriving from these latter stimuli would appear to be necessary for the elaboration of the map of auditory space. This auditory experience operates during a 4 day crucial developmental period from 26 to 30 DAB. This is the same developmental time window as that during which visual experience is required for the construction of th

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00459.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA total of 950 cDNA clones were randomly selected from mouse cerebellar cDNA libraries, and of these, about 130 clones were found to correspond to mRNAs which were expressed unequally between the cerebellum and other parts of mouse brain. Their distribution patterns in adult mouse brain were analysed byin situhybridization, and eight clones were found restricted to specific regions of the brain, including four clones specific to cerebellar granule cells and one clone specific to Purkinje cells. Another 27 clones were preferentially expressed in a diverse, but distinctive subpopulation of brain cells. Among them seven clones were especially abundant in specific nuclei, and three in specific fibre bundles. These clones will be useful in defining new subpopulations of brain cells characterized by different gene expression.

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00460.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractLateral mobility and localization in the surface membrane of the adhesion molecule L1 was studied in morphologically undifferentiated and differentiated neuroblastoma cells to gain insight into its possible association with the different molecular forms of N‐CAM. In undifferentiated cells, the fraction of mobile L1 molecules is high and similar to that of N‐CAM 140. Upon long‐term morphological differentiation, the fraction of mobile L1 molecules is reduced by a factor of three and is similar to that of N‐CAM 180, the predominant molecular form of N‐CAM in differentiated neuroblastoma cells. Comparable to N‐CAM 180, L1 is also preferentially accumulated at contact sites between these cells as seen by indirect immunofluorescence. These observations raise the question of whether at least part of the L1 molecules may be directly or indirectly (e.g. via N‐CAM 180) linked to the cytoskeleton, thus stabilizing cell contacts between differe

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00461.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe aim of the present study was to relate the distribution of efferents of the dorsal subiculum to their origin along the proximo‐distal axis of the subiculum. The distribution of subicular projections was studied in detail by means of the sensitive anterograde tracerPhaseolus vulgaris‐leucoagglutinin (PHA‐L), and the precise origin of these projections analysed with retrogradely transported fluorescent tracers, using double‐ and triple‐labelling protocols. Injections of PHA‐L in the proximal part of the dorsal subiculum, i.e. that part which borders field CA1, result in labelling of the infralimbic, entorhinal and perirhinal cortices, the nucleus accumbens and the lateral septa) region, the interanteromedial nucleus of the thalamus, the core of the nucleus gelatinosus, and the mammillary nuclei, in particular in the rostral parts of the medial nucleus. In contrast, injections in the distal part of the dorsal subiculum, i.e. that part which borders the presubiculum, give rise to labelling in the retrosplenial and postrhinal cortices, the presubiculum, the anterior thalamic complex, the shell of the nucleus gelatinosus, and the mammillary nuclei, preferentially in the caudal part of the medial nucleus. The results of injections of different retrograde tracers, simultaneously placed in two or three targets of the subicular efferents, confirm the results of the anterograde tracing experiments. Moreover, they clearly demonstrate that the population of subicular neurons which, for example, projects to the nucleus accumbens and the interanteromedial nucleus of the thalamus is almost completely segregated from the population that projects to the retrosplenial cortex and the anterior complex of the thalamus. Thus within the dorsal subiculum, populations of neurons can be differentiated so that each population projects to a unique set of target structures. These cell populations are differentially positioned along the proximo‐distal axis. In view of additional evidence indicating that some of the major afferents to the subiculum are organized along the same axis, we suggest that the heterogeneity of the dorsal subiculum along the proximo‐distal axis reflects a general organizational characteristic of this hi

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00462.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractCerebellar slices prepared from newborn rats were co‐cultured with slices derived from the inferior olive of 4‐day‐old rats. After several weeksin vitroolivary fibres projecting into the cerebellar tissue could be assessed by anterograde labelling with the fluorescent dye 1,1‐dioctadecyl‐3,3,3,3′‐tetramethylindocarbocyanine perchlorate (Dil). Following electrical field stimulation of the olivary tissue, all‐or‐nothing complex spikes were generated in Purkinje cells, which closely resembled climbing fibre responses as seenin situ.These responses were completely and reversibly abolished by 6‐cyano‐7‐nitroquinoxaline‐2‐3‐dione (CNQX, 5 μM), an antagonist of non‐N‐methyl‐D‐aspartate excitatory amino acid receptors. Wash in of smaller concentrations of CNQX (0.5–2 μM) resulted in a graded dose‐dependent depression of the climbing fibre‐induced postsynaptic potentials and in a consecutive failure of distinct active components of the complex spikes. With climbing fibre synaptic transmission blocked by CNQX, complex spike‐like potentials could, however, still be evoked by intrasomatic injection of depolarizing current pulses. Increasing the concentration of Mg2+in the bathing solution from 0.5 to up to 8 mM depressed regenerative complex‐spike components. Olivary stimulation elicited only monophasic postsynaptic potentials in Purkinje cells under these conditions. These observations indicate that voltage‐gated conductances which are substantially involved in the generation of the complex spike, are gated by the climbing fibre synaptic depolarization rat

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00463.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY