PHYSIOLOGICAL AND MORPHOMETRIC STUDIES INTO THE PATHOPHYSIOLOGY OF DETRUSOR HYPERREFLEXIA IN NEUROPATHIC PATIENTS

The in vitro responses of isolated detrusor strips obtained from neuro pathic patients with neuropathic bladder dysfunction were found to be supersensitive to both carbachol [ED(50) 1.2 x 10(-6) M. versus 2.5 x 10(-6) M. in control strips; p < 0.005] and potassium chloride [ED(50) 41.8 mM. versus 49.3 mM. in control strips, p < 0.05]. There were no significant differences in the frequency-response curves obtained with intramural nerve stimulation. However, expressed as a percentage of t he maximal response with carbachol, the maximal responses to intramura l nerve stimulation in neuropathic strips were reduced [58.3 +/- 21% v ersus 74.4 +/- 18% for control strips; p < 0.005, Student t test]. Mor phometric studies revealed a lower density of 'presumptive' cholinergi c nerves in neuropathic detrusor (1.0 +/- 1.4 x 10(-4) mu m.(-2) compa red with 3.2 +/- 1.3 x 10(-4) mu m.(-2) in controls, p < 0.05, Mann Wh itney U test). The combined physiological and morphometric results wer e in keeping with a state of postjunctional supersensitivity of neurop athic detrusor secondary to a partial parasympathetic denervation of t he smooth muscle. This may be an important factor in the etiology of d etrusor hyperreflexia. The contractility of neuropathic tissue in resp onse to field stimulation was found to be much lower than normal (2.4 +/- 1.5 g./10 mg. versus 5.9 +/- 3.0 g./10 mg., p < 0.001; Mann Whitne y U test). This reduced contractility to neuronal stimulation might be responsible for some of the characteristics of bladder dysfunction th at are seen in patients with similar neurological conditions.