Relations between spinocervical and post-synaptic dorsal column neurones in the cat

Area of Science:

• Neuroscience
• Spinal Cord Physiology

Background:

• The spinocervical tract (s.c.t.) and post-synaptic dorsal column (p.s.d.c.) pathways are crucial for transmitting sensory information from the spinal cord to the brain.
• Understanding the axonal projections and interconnections of these pathways is essential for elucidating somatosensory processing.

Purpose of the Study:

• To investigate whether axons of the s.c.t. and p.s.d.c. pathways bifurcate, projecting to both the ipsilateral dorsolateral funiculus and dorsal columns.
• To examine the functional link between the s.c.t. and p.s.d.c. pathways by assessing the effects of dorsolateral funiculus stimulation on p.s.d.c. neuronal activity.

Main Methods:

• Single-unit micro-electrode recordings were performed in chloralose-anesthetized cats at the lumbosacral level.
• Axonal recordings and soma-dendritic recordings were made from s.c.t. and p.s.d.c. neurons.
• Electrical stimulation of the dorsolateral funiculus and dorsal columns at cervical levels (C1, C3, C4) was used to antidromically activate neurons and assess pathway interactions.

Main Results:

• None of the examined p.s.d.c. units showed antidromic activation from the dorsolateral funiculus.
• Thirteen out of thirty-three s.c.t. units were antidromically activated from the cervical dorsal columns, with similar latencies to activation from the dorsolateral funiculus.
• Stimulation of the ipsilateral dorsolateral funiculus at C3 facilitated resting activity in 13/25 p.s.d.c. units, while stimulation at C1 had less effect.
• Profound inhibition of resting discharge was observed in 24/25 p.s.d.c. units following stimulation at both C1 and C3.

Conclusions:

• The findings suggest that s.c.t. axons bifurcate and project to both the dorsolateral funiculus and dorsal columns.
• A functional link exists between the s.c.t. and p.s.d.c. pathways, with dorsolateral funiculus stimulation modulating p.s.d.c. neuronal activity through facilitation and inhibition.
• These results contribute to a better understanding of somatosensory information processing in the spinal cord.