A time-course study of urodynamic analyses in rat models with dopaminergic depletion induced through unilateral and bilateral 6-hydroxydopamine injections

Background: Bladder dysfunction is a common non-motor disorder in Parkinson's disease (PD). This study attempted to determine the bladder dysfunction with disease progression in the PD rat model produced from unilateral/bilateral injections of 6-hydroxydopamine (6-OHDA). Methods: Cystometrographic (CMG) and external urethral sphincter electromyographic (EUS-EMG) measurements were scheduled in a time-course manner to determine the disease timing, onset, and severity. Animals were allotted into normal control, unilateral, bilateral 6-OHDA injected groups and subjected to scheduled CMG, EUS-EMG analyses at weeks 1, 2, and 4. Results: The urodynamic results concluded that voiding efficiency (VE) was reduced in both unilateral and bilateral PD rats at all-time points. VE had decreased from 57 ± 11% to 31 ± 7% in unilateral PD rats and in bilateral PD rats, a decreased VE of 20 ± 6% was observed compared to control and unilateral PD rats. The EMG results in unilateral PD rats indicated declines in bursting period (BP) (3.78–2.94 s), active period (AP) (93.38–88.75 ms), and silent period (SP) (161.62–114.30 ms). A sudden reduction was noticed in BP (3.62–2.82 s), AP (92.21–86.01 ms), and SP (128.61–60.16 ms) of bilateral PD rats than in control and unilateral PD rats. Histological evidence exhibited a progressive dopaminergic neurons (DA) depletion in the substantia nigra (SN) region in 6-OHDA lesioned rats. Conclusion: The experimental outcomes strongly implied that significant variations in bladder function and VE decline were due to the depletion of DA neurons in the SN region of the brain.