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Brain Research 780 1998 245–252
Research report
Age-related changes in the morphology of preganglionic neurons projecting
to the paracervical ganglion of nulliparous and multiparous rats
Monica A. Dering, Robert M. Santer, Alan H.D. Watson
)
Anatomy Unit, School of Molecular and Medical Biosciences, UniÕersity of Wales Cardiff, P.O. Box 911, Cardiff CF1 3US, UK
Accepted 23 September 1997
Abstract
The aim of this study was to investigate age-related changes in preganglionic neurons in the lumbar and sacral spinal cord of the
female rat that may underlie impaired control of the urogenital system in old age. Preganglionic sympathetic and parasympathetic neurons
of young adult, aged nulliparous and aged multiparous rats were identified by retrograde tracing with cholera toxin subunit-B and
subsequent immunocytochemistry. Labeled preganglionic neurons were scanned, processed and analyzed using the confocal microscope.
Measurements were made of soma area, number of primary dendrites, number of dendritic branch points and total dendritic length. There
were significant decreases in the number of primary dendrites, number of dendritic branch points and total dendritic length of sympathetic
preganglionic neurons in both nulliparous and multiparous aged rats compared to the young adult group. No significant differences were
found in the dendritic morphology of aged parasympathetic preganglionic neurons. Soma area was not significantly different between age
groups for sympathetic or parasympathetic preganglionic neurons. These changes in dendritic morphology may result in altered control of
the lower urogenital tract in aged nulliparous and multiparous female rats. q 1998 Elsevier Science B.V.
Keywords: Aging; Preganglionic neuron; Cholera toxin; Confocal microscopy; Pregnancy; Pelvic innervation
1. Introduction
In humans and animals, studies of both sexes have
shown that aging is associated with impaired function of
the pelvic viscera. Loss of bladder function is the most
clinically important on account of the high incidence of
urinary incontinence in the elderly population. In females,
however, urogenital problems may additionally occur in
relation to pregnancy or parturition.
In aged men and women, residual volume of urine after
micturition and detrusor instability are increased while
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bladder capacity is decreased 19 . In women, there is also
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a decrease in sensitivity to bladder filling 19 . Changes in
neural input may contribute to the changes in control of
micturition in old age. Electrophysiological recordings in
the rat reveal an age-related decrease in sensitivity of
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pelvic nerve afferents to changes in bladder volume 14 .
At both the light and electron microscopic level, the
percentage of nerve fibers per mm
2
of tissue in human
male and female detrusor muscle is reduced while the
)
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Corresponding author. Fax: 44 1222 874486; E-mail:
watsona@cardiff.ac.uk
percentage of muscle per mm
2
of tissue remains the same
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10 . Degenerating axons are also seen in the aged rat
bladder but not in young adult animals or in a model of
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hypertrophic bladder 16 .
Natural-fill cystometry has shown that the bladder vol-
ume at micturition is not changed significantly in aged rats
compared to young adults, while the intravesicular pres-
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sure at micturition is twice as high 5 . In a subsequent
study, using in vitro cystometry with saline infusion, the
plateau pressure in the aged bladder was found to be
significantly decreased, with no change in bladder capacity
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6 . It is clear, therefore, that removing the neural input of
the bladder alters its properties. This has also been demon-
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strated by denervation of the efferent nerves hypogastric
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and pelvic nerves to the bladder which results in a cessa-
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tion of reflex micturition 14 . Two studies involving in
vivo cystometry with saline infusion have shown that the
volume threshold of micturition is increased in aged rats
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when compared to young adults 14,16 . However, whereas
one of the studies also revealed an increase in the pressure
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threshold of micturition with aging 16 , the other did not
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14 . In view of the conflicting findings resulting from
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different experimental approaches in vivorin vitro, natu-
0006-8993r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.
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PII S0006-8993 97 01199-2