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Afferent pathways from the urinary bladder were examined with axonal tracing techniques in normal female Wistar rats and in those with partial urethral ligation. Following injection of wheat germ agglutinin-horseradish peroxidase (HRP) into the bladder wall, HRP was detected in lumbosacral dorsal root ganglion cells and in afferent projections to the L6-S1 spinal cord at sites in laminae I, II, V-VII, and X known to receive visceral afferent input. Partial urethral ligation (6 weeks) produced a sixfold increase in bladder weight and altered the morphology of bladder afferent pathways. Changes included an increase in the average cross-sectional area of labelled neuronal profiles in L6 and S1 dorsal root ganglia in obstructed (766 +/- 378 microns 2, P less than 0.001) compared to control rats (528 +/- 189 mu 2). The cross-sectional area of the largest profiles also increased by approximately 40%. The mean number of labelled dorsal root ganglion cell profiles was similar in ligated (837 +/- 198) and control (883 +/- 352) groups. When compared to control animals the obstructed animals exhibited a 60% increase in the area of the labelled afferent terminal field in the intermediolateral region of the L6-S1 spinal cord. This increased labelling was even more remarkable given that the volume of tracer per bladder weight injected into the hypertrophied bladder was 87% less than controls. These results provide evidence that bladder afferents project to regions of the spinal cord known to regulate micturition and that these afferents can undergo morphological alterations and/or changes in axoplasmic transport in response to urethral ligation. Changes may occur in response to increased target organ mass, increased neural activity, or alterations in the levels or activity of neurotrophic factors.

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)

Streptozotocin-induced (STZ, 60 mg./kg. I.V.) diabetic male rats underwent cystometrographic (CMG) and electrophysiologic evaluations under urethane anesthesia (1.2 gm./kg.) to determine whether the neural pathways to the urinary bladder are altered in these animals. Diabetic rats (n = 6) in comparison to controls (n = 8) had significantly greater micturition volumes (3.0 +/- 0.8 ml. vs. 0.7 +/- 0.4 ml., p less than 0.001), bladder compliances (0.51 +/- 0.15 cm. H2O/ml. vs. 0.12 +/- 0.09 cm. H2O/ml., p less than 0.001) and bladder weights (225.2 +/- 21.4 mg. vs. 112.2 +/- 18.0 mg., p less than 0.01). No differences were noted in: 1) the thresholds or conduction velocities of axons in the bladder postganglionic nerves, 2) transmission in the major ganglion or 3) the latencies for firing in the supraspinal parasympathetic reflex pathway to the bladder. However, the supraspinal reflex, which was facilitated by bladder distension in 38% of control rats, was not facilitated in any diabetic rats. Another apparent difference in diabetic rats was the absence of spinal reflex response which was noted in 38% of control animals. This study confirmed that CMG changes in STZ-induced diabetic rats are similar to those observed clinically in patients with diabetic autonomic neuropathy, and in addition raise the possibility that these changes are produced by a defect in autonomic reflexes. It is also clear that alterations of the micturition reflex pathway in diabetic rats are distinct from those associated with another type of enlarged, abnormal bladder induced by bladder outlet obstruction.

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