Altered neural control of micturition in the aged F344 rat

The purpose of this study was to determine whether micturition reflexes are altered in aged rats. Voiding frequencies and awake cystometrograms (CMGs) were measured in young (3-5 months old) and aged (24 months) F344 male rat s. Bladder contractions induced by subcutaneous apomorphine and intravesica l capsaicin stimulation were measured using awake CMGs. Urodynamic paramete rs were compared. Aged rats voided less frequently (4.1 vs 6.9 times/18 h, P = 0.006), with a higher volume per void (1.1 vs 0.7 ml, P = 0.02) and had a higher micturitional threshold pressure (8.7 vs 4.6 mmHg, P = 0.0001) th an the young rats. Apomorphine induced a higher frequency of bladder contra ctions in aged animals compared to young animals (5.5 vs 3.1 contractions/m in, P = 0.03). Intravesical capsaicin caused a lower pressure bladder respo nse in the aged rats (38.5 vs 70.6 mmHg, P = 0.01) compared to the young ra ts. Bladder afferents and central micturition pathways may be altered in ag ed rats. Impaired bladder contractility in the elderly may be exacerbated b y reduced sensory input, whereas the propensity for detrusor instability co uld result from altered central processing. This study demonstrated the uti lity of the F344 animal model to study micturitional changes resulting from aging.