The influence of urinary bladder afferents on spinal motoneuron activity is still unclearal, although visceral afferents are known to inhibit somatic spinal cells in animals. The aim of this study was to assess the effects of urinary bladder filling on the excitability of somatic spinal motoneurons. We studied, in 8 healthy subjects and in 5 patients with chronic spinal cord lesions, the conditioning effect of bladder filling on the size of H and F responses recorded from the gastrocnemius muscle and evoked by tibial nerve stimulation at the poplitea fossa. The bladder was filled with saline using a servo-controlled system which allowed the liquid volume and intravisceral pressure (Vieste RP311) to be monitored. Changes in amplitude of the H and of F responses were tested under five conditions: empty bladder (control), medium and maximum bladder filling, and immediately and 5 min after voiding. Ten trials were performed for each condition. We observed an inhibition of H and F responses in healthy subjects. The H reflex amplitude at medium filling corresponded to 74.8±30% that of controls and at maximum filling to 51±29% that of controls. Immediately after voiding, the H reflex amplitude was still 54.2±54% that of controls, whereas 5 min after voiding it recovered to 97.6±31%. By contrast, in patients, bladder filling did not produce any inhibition. The present findings demonstrate that visceral activation (i.e., bladder filling) simultaneously produces an inhibition of a somatic reflex. In conclusion, this model might provide an interesting device for studying the areflexic bladder in humans.
|Issue number||4 SUPPL.|
|Publication status||Published - 2000|
ASJC Scopus subject areas
- Clinical Neurology