Determining Direction of Axonal Flow in the Equine Ramus Communicans by Ultrastructural Examination of the Plantar Nerves 2 Months after Transecting the Ramus.

This research investigates the direction of axonal flow between specific nerves in horses by analyzing the ultrastructural changes in the horse’s plantar nerves after cutting the connecting branch. The findings suggest that this flow moves in both directions, challenging the previous understandings of nerve functioning in the horse’s pelvic limbs.

Objective of the Research

• The research aims to understand the direction of axonal flow in horses, specifically through a neural connection known as the ramus communicans.
• To do this, the researchers transected (or cut across) the ramus communicans, then examined and analysed the subsequent changes in the plantar nerves over a period of two months.

Method

• Sections of plantar nerves were collected from positions just before and after the communicating branch and were processed for electron microscopy.
• The structures of the nerves, such as the myelin sheath, axons, axoplasm, and cytoplasm of neurolemmocytes were examined for indications of changes due to the transection procedure.

Findings

• The researchers observed a range of ultrastructural changes, such as Wallerian degeneration (a process that follows nerve fiber injury), separation of the myelin sheath layers, shrinking of axons, ruptured mitochondria, and vacuolization in both myelinated and non-myelinated fibers.
• All these changes occurred both proximal (near) and distal (far) to the ramus in medial and lateral plantar nerves, indicating that injury affected both upstream and downstream points from the injury site, which suggests bi-directional axonal flow – a important finding that hasn’t been reported before in this context.
• Additionally, they found mature nerves both before and after the ramus, suggesting that not all nerve fibers must pass through the ramus, another important finding for understanding nerve system functioning.

Conclusion

• The researchers conclude that axonal flow in the equine ramus communicans is bi-directional – contrary to previous understanding – and not all nerve fibers pass through the ramus.
• This research contributes to our understanding of nerve system functioning in horses, which could potentially have important implications for neurology and for treating nerve injuries in veterinary practice.