Hypertrophy and reversal of hypertrophy in rat pelvic ganglion neurons

Abstract

An experimental procedure which chronically reduces the lumen of the urethra in adult female rats produced distension of the bladder and conspicuous thickening of its wall, resulting within 6-8 weeks in a ten-fold increase in muscle weight (muscle hypertrophy). During this process, the neurons in the pelvic ganglion that innervate the bladder undergo a large increase in size (neuronal hypertrophy). The average neuronal volume increased by 83%; small neurons became less numerous and large neurons became more numerous than in controls, but there was no increase in the maximum neuronal size. Six weeks after re-operation and removal of the urethral obstruction, the weight of the bladder was reduced (although not quite to the control levels), while the average neuronal size reversed to values very close to controls. In separate experiments, the pelvic ganglion of one side was removed. The nerve fibres in the hemidenervated bladder sprouted, grew and spread to innervate the whole bladder. The neurons in the surviving pelvic ganglion hypertrophied, the average cell volume increasing by 50% in seven weeks. The experiments showed that: (i) the pelvic neurons of adult rats are capable of very extensive growth when the tissue they innervate (bladder muscle) undergoes hypertrophy; (ii) the neuronal hypertrophy is reversible. This was taken to imply that there are factors within the bladder, including trophic substances, that regulate nerve cell volume not only by inducing growth but also by inducing the opposite effect, a cell size reduction; (iii) unilateral ganglionectomy, which did not induce muscle hypertrophy but doubled the amount of muscle innervated by the contralateral ganglion, was followed by marked neuronal hypertrophy.

Estimate of size and total number of neurons in superior cervical ganglion of rat, capybara and horse

“…Enlargement or reduction in the size of the innervated organ (a salivary gland) is followed by an increase or reduction of the sympathetic neurons projecting into it (Voyvodic 1989a). In the rat bladder, hypertrophy of the musculature with outlet obstruction is followed by a marked enlargement of the related ganglion neurons (neuronal hypertrophy) (Steers and De Groat 1988;Steers et al 1990;Gabella et al 1992). An increased production of nerve growth factor (NGF) by the hypertrophic bladder muscle is a major factor in the growth in size of the nerve cell body (Steers et al 1991).…”

Cholinergic and purinergic contribution to the micturition reflex in conscious rats with long‐term bladder outlet obstruction

“…Modi¢cations of bladder smooth muscle and neurons after experimental outlet obstruction were reported, e.g., a massive increase in detrusor smooth muscle cell size [Gabella and Uvelius, 1990], hypertrophy of pelvic ganglion neurons [Gabella et al, 1992], and an altered morphology of bladder a¡erents in dorsal root ganglions [Steers et al, 1991]. Furthermore, several functional changes in the isolated detrusor muscle have been described.…”

In vitro Effect of Amikacin on Rat and Human Detrusor Muscle Contraction

“…Nicotine determines contraction through activation of nicotinic receptors of the parasympathetic neurons in parasympathetic ganglia, that are known to be present within the bladder wall [1] . Moreover, nicotinic receptors are located on other nerve terminals and modulate exocytosis of neurotransmitters acting on detrusor contractile function [16] ; this could explain the dose-dependent contractile response to nicotine of rat detrusor, which is reported to be poor of intramural ganglia [17] .…”