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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 4 (1992), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Transverse sections of rat embryo brainstem (embryonic age 18–19 days) containing the brainstem motor nuclei were explanted, together with a small piece of tongue or skeletal muscle, in a plasma clot and maintained in culture for 2–3 weeks using the roller tube technique. The results show that brainstem motoneurons survived, differentiated and innervated newly formed multinucleated myotubes which displayed large synchronized contractions after 1 week in culture. Muscle fibre contractions could be induced by excitatory amino acid applications and suppressed by curarization. Muscle fibres differentiated normally. During the first week they showed diffuse acetylcholinesterase positivity and multi-innervation. During the second and third weeks the number of motor end-plates was greatly reduced and transverse striation was observed. In the presence of muscle fibres, the brainstem thinned out and spread, becoming one or two cell layers thick, and the motoneurons tended to migrate towards the muscle fibres, becoming clearly observable in the living culture. When the muscle explant was not present, the brainstem explant did not spread and remained several cell layers thick, while acetylcholinesterase-positive cells, presumed to be motoneurons, tended to disappear. The preparation described is well suited for electrophysiological studies of differentiating motoneurons and offers direct access to their dendritic tree, a most desirable feature for patch-clamp or multisite optical recording.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Retractor bulbi motoneurones ; Accessory abducens nucleus ; 6th nerve ; Oculomotricity ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Motoneurones innervating the retractor bulbi muscle in the cat have been identified by retrograde labelling with horseradish peroxidase, by intracellular recording and by intracellular staining with horseradish peroxidase. Their somata are found in an accessory abducens nucleus, analogous to that described in some other species, which consists of a narrow column of cells situated in the lateral tegmental reticular field, above the superior olive and medial to the facial nerve. This column of cells extends over approximately 1.5 mm from P 5.5 to P 7. The retractor bulbi motoneurones number from 80 to 120 and have large, elongated somata which give rise to five or six major dendrites. Their axons cross the reticular formation in a dorso-medial direction to pass through the principal abducens nucleus before turning to leave the brain stem in the 6th nerve. Antidromic latencies ranged from 0.4 to 0.7 ms. Some retractor bulbi motoneurones could also be activated antidromically by stimulation of the lateral rectus muscle nerve.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Medial vestibular neurones ; Nystagmus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Identified medial vestibular neurones were studied before, during and after nystagmogenic labyrinthine stimulation in the Encéphale isolé cat. Motor discharges were simultaneously recorded from the contralateral abducens nerve. 2. 87.9% of the recorded neurones showed changes in tonic firing frequency during repetitive labyrinthine stimulation with no nystagmic modulation in behaviour. 3. The secondary vestibular neurones projecting monosynaptically to the contralateral abducens motoneurones were included in this non-rhythmic population. 4. Only 2% of the recorded population fired rhythmically both during nystagmogenic stimulation and poststimulation nystagmus. These neurones showed plasticity in behaviour regarding the phases of nystagmus recorded from the contralateral abducens nerve. 5. The remaining 10.1% of the medial vestibular neurones were excited or inhibited by repetitive stimulation of the labyrinth but showed burst firing patterns correlated with poststimulation nystagmic discharges.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: Extraocular muscle ; Motor units ; Glycogen depletion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In nembutal anesthetized adult cats, intracellular stimulation of single abducens motoneurones was used to elicit glycogen depletion of their muscle units. Stimulation by short trains (13 pulses at 40 Hz) delivered once a second, was applied for 20 to 110 min. The activation of the motor unit was monitored by intracellular recording of motoneurone action potentials and by EMG. After the end of stimulation, the muscle was excised and frozen to be cut in serial sections that were processed for demonstration of either glycogen, ATPases or SDH. In two experiments, a motor unit could be histochemically identified because 10–15 fibres showed zones of complete glycogen depletion measuring about 5 mm in length. All the depleted fibres had the same histochemical profile: ATPases reactions gave dark staining with alkaline preincubation and light staining with acid preincubation whereas SDH activity was low. In other experiments, prolonged stimulation produced either no depletion at all or very limited zones of partial depletion in a few muscle fibres.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 26 (1976), S. 367-386 
    ISSN: 1432-1106
    Keywords: Medial vestibular neurones ; Vestibulo-abducens reflex arc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The properties of inputs from the horizontal semi-circular canal to neurones of the medial vestibular nucleus have been studied intracellularly in the unanaesthetized encéphale isolé cat. 2. Secondary neurones of the vestibulo-abducens reflex arc were identified by their orthodromic response to labyrinthine stimulation and by antidromic excitation from the contralateral abducens nucleus. 3. The responses of medial vestibular cells receiving only labyrinthine inputs are also described. These were seen to be predominantly excitatory though IPSPs were observed in a few cases. 4. Identified vestibular neurones were intracellularly injected with procion yellow and showed different morphological characteristics correlated with function.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Accessory abducens nucleus ; Spinal trigeminal neurones ; Axonal trigeminal trajectory ; Intracellular recordings ; Intracellular HRP ; Retractor bulbi motoneurones control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Horseradish peroxidase was injected into the somata or axons of neurones located in the nucleus oralis of the spinal trigeminal complex and projecting to the accessory abducens nucleus. A group of 43 axons with electrophysiologically identified responses to the stimulation of three different areas of the face were studied. The latencies of their orthodromic responses following trigeminal stimulation and their pattern of discharges were compared to those of secondary trigeminal neurones and retractor bulbi motoneurones. Labelled trigeminal axons were found to generate collaterals for the accessory abducens nucleus. Terminal ramifications are present in the rostro-caudal part of the motor nucleus where the dendritic arborization of the motoneurones has been described. Connections to facial and trigeminal motor nuclei were also present, suggesting that secondary trigeminal axons distributed the information to the three motor targets at the brain stem level. It is suggested that the trigemino-retractor bulbi reflex is part of facial reflexes involved in orienting reactions, and protective responses resulting in coordinated movements of the facial musculature.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 21 (1974), S. 139-154 
    ISSN: 1432-1106
    Keywords: Electrotonic coupling ; Antidromic responses ; Abducens motoneurone ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The electrical stimulation of the abducens nerve provokes the classical true antidromic invasion of the abducens motoneurone and a depolarization which is often capable of generating full action potentials in the impaled motoneurone. Experiments studying these depolarizations suggest the existence of electrotonic coupling between the abducens motoneurones of the cat. Intracellular activity of the abducens motoneurones was recorded following intracellular stimulation of the impaled neurone and antidromic stimulation of the abducens nerve. Collision between the outgoing action potential and the antidromic volley differentiated the true antidromic spike from the depolarizations which can induce or not action potentials. The latency of the depolarization ranged between 100 and 1200 μsec. Collision demonstrated that the depolarization and the true antidromic action potential have an independent origin. The depolarizations and action potentials which are not conveyed to the motoneurone by its own axon are interpreted to be generated by electrotonic coupling.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1106
    Keywords: Oculomotricity ; Lateral rectus and retractor bulbi motoneurones ; Infraorbital nerve ; Vibrissal pad ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Responses from lateral rectus, medial rectus and retractor bulbi nerves were obtained following electrical stimulation of the vibrissal pad of the cat. Discharges in afferent fibres dissected from the infraorbital nerve were recorded during movements of the vibrissae and following electrical stimulation of the vibrissal pad. Both stimuli activated the same population of Aα fibers. Intracellular records were obtained from lateral rectus motoneurones identified antidromically in the principal abducens nucleus and from retractor bulbi motoneurones similarly identified in the accessory abducens nucleus. EPSPs (3 mV) were recorded in lateral rectus motoneurones following electrical stimulation of the ipsilateral vibrissal pad at a latency of 3.5 ms. Large-amplitude disynaptic EPSPs (15 mV) were recorded in retractor bulbi motoneurones following the same vibrissal stimulation. The synaptic excitation evoked in both lateral rectus and retractor bulbi motoneurones through stimulation of the ipsilateral vibrissal pad induced an early retraction followed by an abduction of the eye ball. The hypothesis is that the vibrissal message might complement other sensory modalities in the generation of patterned eye movements.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-9007
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Experimental measurements of the input resistance were performed using a whole-cell patch-clamp recording technique of presumed motoneurons in unpurified co-culture of the dissociated prenatal rat brainstem, spinal cord, and hindlimb muscle tissues at different terms of thein vitro development. The recorded neurons were then labelled with Neurobiotin. Morphology of 21 completely stained cells was reconstructed and quantified in 3-D space. To estimate the size of the neurons, their total membrane areas and terminal tip numbers were computed. Computer models based on the reconstructed forms were used to evaluate the impact of cell morphology on the input resistance of motoneurons. The membrane resistivity was assumed as passive, uniform, and constant (12,000 Ω·cm2) at all ages studied. We found that changes in the measured input resistance paralleled those in dendritic morphology at all stages of the development, and that computed values correlated well with measured data. Therefore, we conclude that changes in geometry of the neuron may themselves account for evolution of its input resistance during development.
    Type of Medium: Electronic Resource
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