Spinal cord injury may cause bladder hyperreflexia during the urine storage period and voiding dysfunction during the elimination period. LM11A-31 (LM) is a selective nonpeptide p75NTR ligand and blocks p75-mediated cell death and promotes neurogenesis and neurite survival. We conducted this study to examine if LM alleviates the lower urinary tract dysfunction in spinal cord transected (SCT) mice.

Twenty-two female C57BL/6 mice were used for this study. All efforts were made to minimize animal suffering and to reduce the number of animals used. All surgical procedures were conducted under sevoflurane anesthesia. Spinal cord transection was performed by sectioning at the T8-T9 level at 9-week-old. LM (100 mg/kg in distilled water) or vehicle (VHC) was orally delivered beginning 4 hours after injury, and once daily thereafter for 4 weeks. The in vivo evaluation on the SCT mice were performed at 4-week-post-spinalization. Simultaneous recordings of continuous infusion cystometry (30 μl/min) and the external urethral sphincter (EUS)-electromyogram (EMG) activity were conducted under decerebrate, unanesthetized conditions. All values are expressed as means ± SEM. Unpaired t-test was used for statistical analysis, where applicable. For all analyses, P < 0.05 was considered significant.

Fig. 1 shows typical activities of the bladder and the EUS-EMG. A part of Fig. 1a is extended into 1b and 1c in time scale. ‘Actually-collecting volume’ (ACV) and ‘functional bladder capacity’ (FBC) are the ‘infused volume’ (IV) between the last 'notch-like reduction in intravesical pressure’ (noRIP) during a ‘voiding contraction’ (VC) and the first noRIP of the following VC, and the IV between the last noRIP during VC and the time at the pressure for inducing the following VC, respectively (Fig. 1b). 'Max P' is the highest bladder contraction pressure for causing noRIP during each VC. The silence in EUS-EMG activity started approximately 0.11 seconds before the initiation of noRIP (##), and the EMG's silent period (###) is virtually equal to noRIP duration (#) (Fig. 1c).
Storage period: No differences were found between LM and VHC in the number of the ‘non-voiding contractions’ (NVCs) before VC and the IVs for inducing the first NVC and the first VC (Fig. 2).
Voiding period: There were no differences between LM and VHC in the 1st FBC, the 1st ACV and the ‘voiding efficiency’ (VE) (Fig. 2).
Changes during time-course: The difference between LM and VHC in the number of noRIP was found at 80-100 min time points (Fig. 1A). FBC and ACV of LM were markedly decreased during the time-course, in comparison with those of VHC (Figs. 1B and 1C). ‘Sum duration of noRIP’ (Sum Dur noRIP) per contraction at 80-100 min (Fig. 1E) and ‘sum of noRIP’ (Sum noRIP) per contraction at 60-100 min (Fig. 1G) of LM were smaller than those of VHC. No differences were found between the two groups in mean duration of noRIP (Fig. 1D), mean noRIP (Fig. 1F) and Max P for inducing noRIP in each contraction (Fig. 1H).

At the earliest stage of cystometry, there were no differences between LM and VHC in urodynamic variables. At the time-points of 20 min to 100 min, FBC and ACV in VHC were not changed, whereas those in LM were decreased. The latter was associated with the decreases of Sum Dur noRIP and Sum noRIP. This may be partly explained by the greater difference between LM and VHC in No. noRIP at the later stage of the time-course.

LM-treatment neither suppresses the bladder excitability nor ameliorates voiding disturbance in SCT mice. LM rather exacerbates dyssynergic activity of the bladder and the external urethral sphincter.