Morphological plasticity in efferent pathways to the urinary bladder of the rat following urethral obstruction.

Partial urethral ligation in female Wistar rats produces changes in the neural control of the lower urinary tract including bladder hyperactivity and facilitation of a spinal micturition reflex pathway. To gain insight into the mechanisms underlying these changes, axonal tracing studies were conducted to examine the postganglionic efferent limb of the micturition reflex pathway which originates in the major pelvic ganglion (MPG). Forty microliters of the tracer Fluoro-Gold (4%) were injected into the right side of the bladder in urethral-obstructed (n = 10) and control (n = 4) rats 6 weeks after urethral ligation or sham surgery. As a control Fast blue (40 microliters, 5%) was injected into the colon to label neurons in the MPG innervating the intestine. Obstructed rats exhibited a 6-fold increase (p less than 0.001) in bladder weight (0.848 gm) compared to controls (0.148 gm). A significant increase (p less than 0.001) in the size of labeled bladder postganglionic neurons in the MPG was noted in obstructed rats (576.4 microns 2, n = 4) as compared to controls (299.6 microns 2). However, labeled, colon postganglionic neurons in the MPG in obstructed (312.9 microns 2) rats were not enlarged compared to controls (359.4 microns 2). Neuronal hypertrophy was not associated with a change in the number of labeled MPG neurons in control and obstructed groups.(ABSTRACT TRUNCATED AT 250 WORDS)