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Biomedical subjects

M Shimamura

Publications and source records attributed to M Shimamura.

At least 181 records · Page 10Linked to original sources
PubMed1977

Neural mechanisms of the corneal blinking reflex in cats.

Neural mechanisms of the blinking reflex elicited by corneal stimulation were analyzed with electrophysiological techniques in the encéphale isolé cat. (1) Mechanical and electrical stimulation elicited two successive responses of the electromyogram of the orbicularis oculi. Neuromuscular unit studies revealed that the same unit was excited twice and that the latencies of both responses corresponded well with the two EMG responses. (2) The late response was easily affected by anoxia and pentobarbital administration, and was also abolished with the slow-wave sleep stage. (3) Both responses were abolished by ipsilateral transection between the inferior colliculus and genu of the facial nerve. (4) Compared with the latencies of the EMG, the sum of the conduction times through the sensory trigeminal nucleus and the facial nucleus corresponded with the latency of the early response. The sum of the conduction times through the reticular formation, added to the former reflex arc, corresponded to the latency of the late response. (5) The reflex pathway of the early response is consistent with a three-neuron arc passing through the sensory trigeminal nucleus and the facial nucleus. The late response may employ a multisynaptic arc passing through the brain stem medial reticular formation between the sensory trigeminal nucleus and the facial nucleus.

Animals↗
PubMed1976

Ascending spinal tracts of the spino-bulbo-spinal reflex in cats.

Twenty-six chloralosed cats were employed in order to determine spinal ascending pathways of the spino-bulbo-spinal (SBS) reflex evoked by stimulation of the sural nerve. 1. Partial spinal transection of the dorsal part of the lateral funiculus abolished the SBS reflex ipsilateral to sural nerve stimulation. 2. By recording spinal cord potentials in response to sural nerve stimulation two pathways were established in the dorsolateral funiculus as the spinal ascending tracts of the SBS reflex; one is the direct pathway to the bulbar reticular-formation (direct spino-reticular tract) and the other one (indirect spino-reticular tract) is the relayed by the lateral cervical nucleus. Direct stimulation of the dorsolateral funiculus at the lumbar level elicited the SBS reflex. 3. Short-latency unit discharges were recorded from axons of the direct spino-reticular tract by sural nerve stimulation. These axons were discharged antidromically by stimulation of the bulbar reticular formation. 4. Intracellular recordings from the neurons of the lateral cervical nucleus revealed that spike potentials, riding on EPSPs, were induced by sural nerve stimulation and antidromic firings were obtained by stimulation of the bulbar reticular formation. 5. Neurons originating the spino-reticular tract, direct and indirect, were located in the Rexed V-VII laminae in the lower lumbar segments. They were fired monosynaptically by sural nerve stimulation and antidromically by stimulating the dorsolateral funiculus of the lumbar segments. Among them, some were activated antidromically by stimulating the bulbar reticular formation.

Animals↗