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G Horcholle-Bossavit

Publications and source records attributed to G Horcholle-Bossavit.

At least 55 records · Page 3Linked to original sources
PubMed1979

[Oculomotor reflex evoked by vibrassae stimulation in the cat].

The oculomotor effects of vibrissae stimulation have been studied in the "encéphale isolé" non-anaesthetized Cat. Intracellular recording of lateral rectus motoneurones showed an excitatory projection via the ipsilateral infraorbital nerve to these motoneurones. The afferent fibers are type A alpha, recuited with a low threshold (0.2-0.5 mA) and convey information about vibrissae displacement.

Afferent Pathways↗
PubMed1979

[Interaction between the vestibulo-ocular and the oculomotor systems].

Optomotor nystagmic activity has been elicited in the "encéphale isolé" cat during repetitive electric stimulation of selective oculomotor regions of the frontal cortex and superior colliculus. These regions were nystagmogenic only when facilitated by a cortical arousal or a vestibular activation.

Animals↗
PubMed1979

Anatomical and electrophysiological identification of motoneurones supplying the cat retractor bulbi muscle.

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. The 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.

Abducens Nerve↗
PubMed1979

Morphological characteristics of lateral rectus motoneurones shown by intracellular injection of HRP.

The morphology of identified lateral rectus motoneurones is described after staining by intracellular iontophoresis of horseradish peroxidase. Soma vary in shape and size according to the number and orientation of primary dendrites. The basic pattern of arborisation shows short primary dendrites which branch close to the soma, forming a distal ramification extending over 600 to 1,200 micrometer from the soma. Distal dendrites extend into the ipsilateral medial vestibular nucleus, the reticular formation and amongst the fibres of the medial longitudinal fasciculus. This extension is greater than that previously seen in procion yellow and Golgi stained lateral rectus motoneurones. The axon originates from the perikarya or from the base of a primary dendrite. No axon collaterals have been observed.

Abducens Nerve↗
PubMed1978

[Electrotonic transmission in the mammalian central nervous system (author's transl].

The aim of this review is to present the electrophysiological data, obtained in the mammalian central nervous system, which show that depolarisations recorded intracellularly, under certain experimental conditions can be interpreted in terms of electrotonic coupling. The results were obtained from very different structures: primary sensory nuclei, sensori-motor integration centres and motor nuclei. The association of the phenomenon of electrotonic transmission with a known ultrastructural substrate--the "gap junction"--has been defined by the term electrotonic coupling. In the cases where it has not been possible to link depolarisations with the presence of gap junctions, other possible morphological correlates have been envisaged. The functional significance of electrotonic interactions are discussed on the basis of information obtained from different experimental approaches.

Animals↗
PubMed1978

[Electrophysiology of vestibulo-ocular reflexes].

Electrophysiological and morphological properties of premotor neurones in the vestibulo-ocular system have been studied intracellularly in the unanesthetized "encéphale isolé" cat. 1. Secondary neurones of the vestibulo-abducens reflex, identified both by their antidromic and orthodromic responses, showed no nystagmic modulation of their activity. 2. Only 12% of the recorded population in the medial vestibular nucleus showed burst firing patterns correlated with the phases of nystagmus. 3. Two classes of neurones which did not respond to stimulation of the abducens nerve were recorded in the abducens nucleus. The first were inhibited by phasic vestibular stimulation and fired 180 degrees out of phase with the ipsalateral motor nerve discharge. The second type of neurones was excited by vestibular stimulation and fired in synchrony with the motor nerve activity.

Abducens Nerve↗
PubMed1977

[Interaction between visual activation and proprioceptive activation in neurons of the superior colliculus].

Units located in the superficial and intermediate layers of the superior colliculus are activated by proprioceptive stimulation of the extraocular muscle nerves as well as by specific visual stimuli. Units of the deep layer of the colliculus, not sensitive to visual activation, are inhibited by proprioceptive stimulation. A few of the units showed interaction between the two types of stimulation, the proprioceptive response appearing only when spontaneous activity was decreased by a visual stimulus.

Animals↗
PubMed1977

Direct excitatory interactions between spinal motoneurones of the cat.

1. Ninety-seven spinal motoneurones were identified by their antidromic invasion following stimulation of the muscle nerve and submitted to a series of four tests to reveal a possible direct excitation between motoneurones. 2. Threshold differentiation, refractoriness, hyperpolarization and collision revealed antidromically induced depolarizations in fourteen of the ninety-seven tested motoneurones. 3. The parameters of the antidromically induced depolarizations indicate a short latency, a low amplitude and independence with regard to the membrane polarization. 4. It is concluded that the antidromically induced depolarizations reached the impaled motoneurone via a route other than its own axon. 5. The mechanism may involve either electrotonic interactions between neighbouring motoneurones or excitatory recurrent collaterals between synergist motoneurones.

Action Potentials↗
PubMed1976

Horizontal vestibular nystagmus. I. Identification of medial vestibular neurones.

1. The properities 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 bestibulo-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 in puts 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.

Abducens Nerve↗
PubMed1976

Horizontal vestibular nystagmus. II. Activity patterns of medial vestibular neurones during nystagmus.

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 repetitibe 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 pattersn correlated with poststimulation nystagmic discharges.

Abducens Nerve↗
PubMed1975

Mesencephalic porjections of the rectus lateralis muscle afferents in the cat.

Responses to passive stretch applied to the rectus lateralis muscle (RL) were recorded with a microelectrode from the mesencephalic nucleus of the fifth nerve (Mes V) in cat encéphale isolé preparation. The necessary conditions to attribute the unit response to an eye muscle stretch are the followings: i) respond neither to jaw movements nor to pressure applied to the eye ball: ii) be activated with a short latency, following stretch of the eye muscles; iii) be excited by a light touch applied to a small area of one eye with a glass rod. The characteristics of the Mes V responses following stretch of the eye muscle are similar to those obtained in a primary afferent fibre from a skeletal muscle. Horseradish peroxidase was injected in the RL muscle of young and adult cats. As a consequence of fast retrograde axonal transport, the tracer was found to accumulate in the corresponding motoneurones of the VI nucleus. In addition, the enzymes accumulation was also found in cells of Mes V corresponding to the somata of RL sensory terminals. Units responding to RL stretchs, and primary sensory neurons labelled by the tracer, were found in the same area of Mes V.

Animals↗