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Biomedical subjects

M Aoki

Publications and source records attributed to M Aoki.

At least 847 records · Page 47Linked to original sources
PubMed1976

Ascending long spinal actions on forelimb motoneurons in the acute spinal cat.

Ascending long spinal reflex system were investigated by means of monosynaptic reflex testing in the acutely spinalized unanesthetized cat. 1. Hindlimb nerve stimulation gave bilateral facilitatory effects on the motoneuron pools of pectoralis major and physiological flexors of the forelimb such as biceps brachii, extensor carpi radialis, extensor digitorum communis, but elicited depressive effects on the physiological extensors such as triceps brachii, flexor carpi radialis, flexor digitorum profundus. 2. In the latissimus dorsi, which is the antagonist of pectoralis major, a depressive effect was elicited by the stimulation of ipsilateral hindlimb nerves, and a facilitatory effect by contralateral stimulation. 3. These effects were evoked mainly from group II afferent fibers in muscle as well as cutaneous nerves. 4. Intracellular recordings from motoneurons of extensor carpi radialis revealed EPSPs following stimulation of hindlimb nerves with time courses corresponding to those of the facilitatory effects. We failed to detect any potential changes in the motoneurons of flexor carpi radialis following stimulation of hindlimb nerves.

Afferent Pathways↗
PubMed1976

Long spinal and pyramidal actions on hindlimb motoneurons of the marsupial brush-tailed possum, Trichosurus vulpecula.

The existence of descending propriospinal reflex linkages between forelimbs and hindlimbs has been established in the brush-tailed possum (Trichosurus vulpecula). In animals under chloralose anesthesia and with intact brain stem, forelimb volleys evoked facilitation of flexor and extensor monosynaptic reflexes of both hindlimbs, more pronounced on the ipsilateral side. Powerful inhibition of briefer latency and restricted to ipsilateral flexor digitorum longus (FDL) motoneurons was also brought about by forelimb volleys; at latencies exceeding 20-30 ms, FDL inhibition was usually replaced by facilitation. Distinctness of the two long spinal actions was shown by differences in forelimb receptive fields and in threshold of the executant afferent fibers. The field for reflex inhibition was located distally in the forepaw region, that for facilitation being wider, including deep as well as superficial tissues. Threshold of afferent fibers evoking inhibition was lower than that for facilitation. The descending long spinal actions were compared with those set up by repetitive stimulation of the motor cortex contralateral to the test hindlimb reflexes. In agreement with previous work, strong facilitation of most flexor or extensor motoneurons was produced, including those of quadriceps and ankle flexors, as well as gastrocnemius and hamstring motor nuclei; inhibition consistently appeared only in the FDL motoneuron pool. Weak and inconstant inhibitory action was occasionally observed in other motor pools. Pyramidal tract section abolished the cortical inhibition of FDL, but had little effect on facilitation; both long spinal actions were unchanged. Pyramid-sparing brain stem section greatly reduced both cortical and long spinal facilitatory action, but had little or no effect on FDL inhibition from either source. Interaction experiments demonstrated facilitation of weak inhibitory actions on FDL motoneurons of forelimb and cortical stimulation when elicited together, suggesting a sharing by the two inputs of common interneuronal elements. The observation is consistent with the notion that the long propriospinal system responsible for FDL inhibition from the forepaw might provide the pathway for pyramidal inhibition of the same group of motoneurons.

Animals↗
PubMed1976

[Photic epilepsy].

Fourteen cases of patients with photoconvulsive response during intermitent luminous stimulation (eleven women and three men) are reviewed. The frequency of the photoconvulsive response was higher between 10 and 20 years of age (eleven cases). Most of the patients (twelve) presented some form of epilepsy and only two had psychomotor retardation without epilepsy. Comment is made on differences published by other authors and possible explanations of such differences are proposed.

Adolescent↗
PubMed1975

Cortical and long spinal actions on lumbosacral motoneurones in the cat.

1. The effects of stimulating forelimb afferents on various ipsilateral motoneurones of the hind limb have been compared with those of volleys set up in the contralateral pericruciate cortex in cats anaesthetized with chloralose. 2. With intact neuraxis, brachial plexus volleys evoke discharge of flexor and extensor motoneurones; short cortical tetani also elicit discharge mainly of flexor motoneurons. After a pyramid-sparing brainstem lesion, little or no firing is evoked by either input. 3. Monosynaptic reflex testing and intracellular recording reveal subthreshold actions on hind-limb motoneurones, inhibition of FDHL and later facilitation of extensors and flexors by forelimb volleys, facilitation of flexors and extensors together with inconstant inhibition of the latter, by cortical stimulation. 4. Interruption of medullary extrapyramidal paths greatly reduces intensity and duration of facilitation from the forelimb, and largely removes cortically evoked extensor facilitation. Inhibition of FDHL from forelimb and cortex is unchanged; cortical volleys continue to facilitate flexors, and have mainly inhibitory action on extensors in these 'pyramidal' preparations. 5. Hyperpolarization of FDHL motoneurones occurs in response to forelimb and cortical volleys, of time course corresponding to depression of test reflexes. Spinal pathways responsible for the two inhibitory actions are independent, and unless each is very strong, their separate actions summate when elicited together. 6. Receptive field for FDHL inhibition from the forelimb is located distally in the forepaw, and its receptors are largely served by cutaneous fibres of low threshold; some Group II fibres in distal muscle nerves also contribute. Receptive field for facilitation embraces the whole limb, and the executant afferent fibres are of higher threshold. 7. Natural stimulation of the forelimb can evoke the long spinal actions, vibration or light pressure on the forepaw eliciting FDHL inhibition, and strong pinching evoking the more general facilitation. Possible functional roles of these actions in the intact animal are discussed.

Animals↗