Mechanosensitive primary bladder afferent activity in rats with and without spinal cord transection

Area of Science:

• Neuroscience
• Urology
• Spinal Cord Injury Research

Background:

• Spinal cord injury (SCI) causes significant changes in bladder function and associated nerve pathways.
• The precise alterations in the excitability of bladder afferent nerve activity following SCI remain incompletely understood.
• Investigating peripheral mechanosensitive bladder afferents is crucial for understanding SCI-induced bladder dysfunction.

Purpose of the Study:

• To characterize peripheral mechanosensitive bladder afferents in the pelvic nerve.
• To identify changes in Adelta and C fiber afferent activity after spinal cord injury.
• To determine the relationship between fiber type and functional properties of bladder afferents post-SCI.

Main Methods:

• Adult female rats were divided into spinal cord injured (Th9 transection) and neurologically intact groups.
• Single unit afferent activity from L6 dorsal root filaments was monitored.
• Bladder afferent fibers were identified and their activity recorded during constant saline filling.

Main Results:

• Two distinct afferent patterns (accelerated and nonaccelerated) were observed during bladder filling.
• The incidence of the accelerated afferent pattern was significantly higher in SCI rats for both Adelta and C fibers.
• No correlation was found between conduction velocity and the functional properties of these afferent fibers.

Conclusions:

• Mechanosensitive bladder afferent activity exhibits diverse patterns and is facilitated post-SCI.
• This facilitation is particularly evident during small bladder contractions (micromotions).
• The functional properties of individual afferent fibers do not appear directly related to their conduction velocity or fiber type.