"Spinal Cord" - what is it, definition of the term
In rodents such as rats and mice, the central nervous system contains a slender, elongated bundle of nerve tissue that extends from the medulla oblongata through the vertebral canal, composed of paired gray‑matter cores surrounded by white‑matter tracts; this structure transmits descending motor commands to peripheral nerves and ascends sensory information to the brain, and it is protected by meninges and the surrounding vertebral arches.
Detailed information
The central nervous conduit extending within the vertebral canal of rats and mice measures approximately 3 cm in adult rats and 2 cm in adult mice. It consists of 31–33 segmental units, each defined by a pair of dorsal and ventral roots that emerge from the surrounding bone.
Gray matter occupies the interior, forming a butterfly‑shaped region that houses interneurons, motoneurons, and sensory relay cells. The dorsal horns receive afferent input from peripheral receptors, while the ventral horns contain the cell bodies of motor neurons projecting to skeletal muscles. White matter surrounds the gray core, organized into longitudinal tracts that carry ascending sensory information and descending motor commands.
Development proceeds from the neural tube, with primary neurogenesis occurring between embryonic days 9 and 12 in mice and days 10 and 13 in rats. Axonal pathways establish functional connectivity by embryonic day 14, and myelination intensifies during the first postnatal week, reaching adult levels by postnatal day 30.
Key functional pathways include:
- Dorsal column–medial lemniscal tract: conveys fine touch and proprioceptive signals to the brainstem.
- Spinothalamic tract: transmits nociceptive and temperature information.
- Corticospinal tract: delivers voluntary motor commands from the cerebral cortex.
- Rubrospinal and reticulospinal tracts: mediate involuntary and reflexive motor outputs.
Experimental models frequently employ this structure for injury studies. Common lesion types are:
- Contusion injury induced by calibrated impactors.
- Compression injury using calibrated forceps.
- Transection models that sever specific segments.
These models enable investigation of axonal regeneration, glial scar formation, and functional recovery. Molecular analyses often focus on markers such as NeuN for neuronal nuclei, GFAP for astrocytic activation, and MBP for myelin integrity. The rodent neural conduit thus provides a compact, well‑characterized platform for probing central nervous system physiology and pathology.