Elsevier

Brain Research

Volume 172, Issue 1, 17 August 1979, Pages 13-21
Brain Research

Reticulospinal tracts involved in the spino-bulbo-spinal reflex in cats

https://doi.org/10.1016/0006-8993(79)90892-8Get rights and content

Abstract

Twenty-three chloralosed cats were used to examine the spinal descending pathways of the spino-bulbo-spinal (SBS) reflex.

Transection of the ventrolateral funiculus in the spinal cord at the thoracic level abolished the SBS reflex of caudal spinal segments ipsilateral to the transection, but did not abolish the ascending propriospinal reflex and SBS reflex of rostral segments.

Unit discharges elicited in axons of the ventrolateral funiculus at L3 by sural nerve stimulation had the appropriate latency for mediating the SBS reflex. These axons originated in the medial bulbar reticular formation, since the responses had a consistent short latency and followed repetitive stimulation of the bulbar reticular formation (up to a rate of 300 Hz). Conduction velocities of reticulospinal axons ranged widely from 20 to 120 m/sec. There were two peaks, fast (95 m/sec) and slow (35 m/sec). The fast conducting fibers showed oligo-spikes, high amplitude and wide distribution of latency. Almost 90% of the axons with slow conduction exhibited multi-spikes, low amplitude and narrow distribution.

Unitary responses of the ventral rootlet at L7 were elicited by sural nerve stimulation and correlated with the latency of the SBS reflex. The unitary response was also evoked by train pulse stimulation of the ventrolateral funiculus in the spinal cord. Conduction velocities of descending spinal tracts ranged from 20 to 60 (mean±S.D.,35 ± 8) m/sec.

We may conclude that the descending spinal pathway of the SBS reflex is the slowly conducting reticulospinal tract which originates in the medial bulbar reticular formation and passes through the ventrolateral funiculus of the spinal cord.

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