[SECOND MESSENGERS IN PRESYNAPTIC REGULATION OF GLYCINERGIC SYNAPSE ON THE FROG MOTONEURON].

The possible pathways of inhibitory influences mediated by two kinds of metabotropic receptors, group III metabotropic glutamate receptors (mGluRs III) and GABAB receptors (GABABRs) to the miniature glycinergic events were investigated in the isolated spinal cord of the frog Rana ridibunda. The glycinergic events prevailed within the miniature inhibitory activity of motoneurons [3]. Selective agonists of GABABRs (baclofen) and group III mGluR (LAP4) reduce the frequency of miniature events to 48.

[Dorsal root afferent fiber termination in the spinal cord of the turtle Testudo horsfieldi and 3-dimensional reconstruction of the sensory-motoneuron connection].

HRP tracing methods and computer reconstruction were used to study the structural organization of sensory-motoneuron connections in the turtle. HRP was applied through suction electrodes to thin dorsal and ventral root filaments of superfused isolated lumbar spinal cord of the turtle Testudo horsefieldi. Single motoneurons were labeled iontophoretically with the use of intracellular glass microelectrodes.

[The role of group II and III metabotropic glutamate receptors in modulation of miniature synaptic activity in frog spinal cord motoneurons].

The results of present work demonstrate significant modulating effects mediated by group II and III mGluRs on miniature postsynaptic potentials (mPSP) of the frog spinal motoneurons. The mode of group II and III mGluRs ligands influences, i. e.

Comparative study of spinal motoneuron axon collaterals.

Numerous spinal motoneurons in mammals possess recurrent axon collaterals included in a feedback loop for controlling motoneuron activity. For nonmammalian vertebrates, the data concerning the existence of collaterals and their intraspinal branching are fragmentary and contradictory. We focused on axonal branching of motoneurons in lampreys, frogs, turtles and young rats, using light microscopic analysis of HRP- or neurobiotin-labeled motoneurons.

[Modulation of miniature inhibitory potentials in motoneurons of the turtle spinal cord by group II metabotropic glutamate receptors].

The role of group II metabotropic glutamate receptors (mGluRs) in modulation of inhibitory synaptic activity was studied by intracellular recording of motoneuron miniature inhibitory spontaneous postsynaptic potentials (mIPSPs) in isolated lumbar segments of the turtle spinal cord in the medium containing TTX, CNQX, AP-5. The ratio of mIPSPs with fast and slow kinetics (83% vs 17%) is in accordance with the ratio shown for glycine- and GABA-mediated IPSP or IPSCs (Jones et al., 1988; Gao et al.

[Recurrent axon collaterals of lumbar motor neurons in turtles].

A combined morphophysiological study was made of connections between motoneurons on the superfused isolated lumbar spinal cord of Testudo horsfieldi. Postsynaptic potentials of motoneurons, followed by antidromic stimulations of ventral root filaments (VR-PSPs), were recorded intracellularly. Depolarizing VP-PSPs had short latencies (1.

Structural and physiological properties of connections between individual reticulospinal axons and lumbar motoneurons of the frog.

Although the direct, monosynaptic influence of brainstem projections onto motoneurons is well-known, detailed morphological studies on the synaptic contact systems and a correlation with their functional properties are largely lacking. In this work, 43 pairs, each formed by a reticulospinal fiber contacting a lumbar motoneuron, were identified and studied electrophysiologically. Four of these were successfully labeled intracellularly with horseradish peroxidase (HRP) or neurobiotin and reconstructed using a computer-assisted camera lucida with high resolution.

Electron microscopic serial analysis of GABA presynaptic terminals on the axon hillock and initial segment of labeled abducens motoneurons in the rat.

The aim of the present study was to provide a quantitative analysis of the synapses made onto the axon hillock and initial segment of rat abducens motoneurons retrogradely or intracellularly stained with HRP. GABA-immunoreactive terminals contacting these axons were visualized using a postembedding procedure. The presynaptic terminals contained either spherical or pleomorphic vesicles.

Comparison of the topology and growth rules of motoneuronal dendrites.

The complexity, shape, and branching modes of the dendrites of spinal motoneurons were compared in cat, rat, and frog using topological analysis and growth models. The complexity of motoneuronal dendrites, measured as the mean number of terminal segments, varied significantly among samples and was related to contractile properties of innervated motor units. Despite this variation, all mature motoneurons having a mean number of terminal segments per dendrite greater than ten (up to 24.

Structure of recurrent axon collaterals of frog lumbar motoneurons as revealed by intracellular HRP labelling.

Iontophoretical injection of horseradish peroxidase (HRP) into lumbar motoneurons of the isolated and perfused frog spinal cord allowed to reveal recurrent axon collaterals of motoneurons and to study their structural organization. The axons of about 50% of stained motoneurons gave rise to recurrent collaterals. Motoneurons emitted usually one and in a few cases two recurrent axon collaterals.

[A light microscopic study of the axonal collaterals of the lumbar motoneurons in the spinal cord of the frog Rana ridibunda].

By using intracellular injection of horseradish peroxidase into the lumbar motoneurones of the isolated spinal cord of the frog Rana ridibunda the structure of axon collaterals was studied. It was shown that about 50% of the HRP-stained cells had mainly one axon collateral of the 1st order. The subsequent branching patterns of the collaterals showed considerable variations.

Relation between structural and release parameters at the young rat sensorimotor connection.

The present work was carried out on isolated spinal cords of young rats. The aim of this study was the combined morphological and electrophysiological investigation of sensorimotor connections labelled with horseradish peroxidase and the evaluation of the relationship between their structural and functional properties. Sensorimotor contacts were widely distributed along the postsynaptic cell: from the soma and juxtasomatic dendrites to distal dendrites.

Sensorimotor connections in the lumbar spinal cord of the young rat: a morphological study.

A morphological investigation of sensorimotor connections was performed on the isolated lumbar spinal cord of 8-15-day-old rats using horseradish peroxidase labelling techniques. Horseradish peroxidase was applied to the filaments of dorsal and ventral roots and injected intracellularly into motoneurons. The labelled afferent fibres and their contacts on motoneurons were examined under a light microscope.

[Morphologic and quantum characteristics of sensomotor neuron synapses in isolated rat spinal cord].

The structural-functional relationships of sensorimotor connections were studied in isolated lumbar cord segments of 7-14 day-old rats. Individual motoneurons were found to have synaptic contacts only with a single collateral of the afferent fibre. The number of contacting boutons gained 10.

[Mechanisms of motor neuron interaction in the isolated spinal cord of rat pups].

Interactions between lumbar motoneurons were studied by intracellular recording of responses to stimulation of ventral roots and intracellular HRP injection in isolated spinal cord preparations of immature (9-14 days old) rats. Ventral root-evoked electrotonic potentials in individual motoneurons were due to interconnections with few other motoneurons and could not elicit spike potentials. Direct chemical excitatory interactions of motoneurons were also found which may occur via axon collaterals.

[Morphological bases of motor neuron interaction in the isolated spinal cord of rat pups studied with horseradish peroxidase].

The structure of connections of the lumbar motoneurons was investigated in the isolated spinal cord of young rats by the HRP methods. HRP was applied to the ventral roots and injected intracellularly into the motoneurons. The light microscopic study has shown that dendrodendritic, dendrosomatic and somatosomatic contacts between motoneurons might be established.

Morphophysiological characteristics of connexions between single ventrolateral tract fibres and individual motoneurones in the frog spinal cord.

In experiments on the isolated frog spinal cord, simultaneous intracellular recordings were performed from synaptically connected individual ventrolateral tract fibres and lumbar motoneurones. Statistical parameters of amplitude fluctuations of unitary excitatory postsynaptic potentials evoked by direct activation of presynaptic axons were compared with the number of synaptic contacts at the same connexions revealed by staining both pre- and postsynaptic elements with horseradish peroxidase. Close correspondence between the number of contacting boutons and that of release elements (n) determined from binomial relations was observed.

[Intracellular activity of potassium in frog spinal cord motor neurons].

Intracellular K activity (aik) in frog motoneurons of isolated spinal cord as measured by double-barrelled K+-selective microelectrodes revealed mean values as follows: 74.8 +/- 2.5 mM at the beginning of the recording and 51.

[Quantitative determination of potassium content of spinal motor neurons frogs by x-ray microanalysis].

X-ray microanalysis has been made of the potassium content of motoneurons in the frogs Rana ridibunda and R. temporaria. The tissue was frozen in isopentane up to-160 degrees, dried in vacuum at-50 degrees, embedded into epoxy resin and sectioned by ultramicrotome.