Parasympathetic preganglionic neurons in the sacral spinal cord

Area of Science:

• Neuroscience
• Autonomic Nervous System Research
• Urology Research

Background:

• The sacral parasympathetic nucleus (SPN) controls autonomic functions.
• Understanding neuronal subtypes in the SPN is crucial for bladder and bowel control.

Purpose of the Study:

• To differentiate and characterize two types of preganglionic neurons in the cat's SPN.
• To elucidate their distinct roles in micturition and defecation reflexes.

Main Methods:

• Electrophysiological recordings of neuronal activity.
• Axonal conduction velocity measurements.
• Histological analysis of neuronal morphology and location.

Main Results:

• Identified myelinated B-PGNs innervating the bladder and unmyelinated C-PGNs innervating the large intestine.
• B-PGNs are activated by bladder distention, C-PGNs by rectal stimulation.
• Spinal cord transection disrupts micturition, but a compensatory C-fiber reflex emerges in chronic spinal cats.

Conclusions:

• The micturition reflex involves a simple on-off switch circuit activated by A delta afferents.
• A distinct C-fiber mediated spinal reflex contributes to bladder function recovery after spinalization.
• Neuronal plasticity allows for alternative reflex pathways following spinal cord injury.