Urinary bladder innervation in children

Species differences in the distribution of beta-adrenoceptor subtypes in bladder smooth muscle

1. The beta-adrenoceptor (beta-AR) subtypes mediating relaxation of the rabbit, rat and canine detrusors were subjected to functional investigation using selective beta-AR agonists and antagonists. 2. In all three species, isoprenaline, noradrenaline and adrenaline each produced a concentration-dependent relaxation of the detrusor. The rank order for their relaxing potency was isoprenaline>adrenaline>noradrenaline in rabbits and rats, but isoprenaline>noradrenaline>adrenaline in dogs. 3. Dobutamine did not produce relaxation of the detrusors at concentrations that are selective for beta1-AR. The selective beta2-AR agonist, procaterol, had a more potent relaxing effect on rabbit and rat detrusors than on the canine detrusor. CGP-12177A, a selective beta3-AR agonist, was more effective in the rabbit than in the other two species. On the other hand, the relaxing effect of another beta3-AR agonist, CL316243, was more pronounced in dogs and rats than in rabbits. 4. CGP-20712A (10(-9) to 10(-7) M), a selective beta1-AR antagonist, caused a slight rightward shift of the concentration-relaxation response curve for isoprenaline in the canine detrusor (pA2 9.41), but not in the rabbit and rat detrusors. ICI-118,551, a selective beta2-AR antagonist, antagonized the isoprenaline-induced relaxation in rabbits (pA2 9.45) and rats (pA2 9.05), but not in dogs. Bupranolol, a non-selective beta-AR antagonist, caused a rightward shift of the concentration-relaxation curve for isoprenaline in the rabbit (pA2 9.32) and rat (pA2 8.98). However, higher concentrations (3 x 10(-8) to 10(-5) M) were needed to induce a rightward shift of the curve for isoprenaline in the dog (pA2 8.19) than in the other two species. 5. We have confirmed that the distribution of beta-AR subtypes in the detrusor muscle varies significantly from species to species and we provide here the first evidence of the presence of beta3-AR in the detrusor. It is suggested that the relaxation induced by adrenoceptor agonists in urinary bladder smooth muscle may be mediated mainly via beta2-AR in rabbits, via both beta2- and beta3-AR in rats, but mainly via beta3-AR in dogs.

Alpha-adrenoceptor function before and after chemical sympathectomy in human and feline detrusor muscles

Isolated bladder segments from man and cat were treated with 6-hydroxydopamine (6-OHDA) in vitro. Chemical sympathectomy was evaluated with fluorescence microscopy and found to be very similar to the effect of 6-OHDA administered in vivo to cats. Isometric smooth muscle contractile responses were induced by field stimulation (FS). The amplitude of the responses increased after denervation. The effects of alpha-adrenoceptor agonists and antagonists on the FS-induced contractile responses were compared before and after treatment with 6-OHDA. The reduction in the contractile responses after the addition of noradrenaline to the feline bladder strips was more pronounced after treatment. Phentolamine induced an increase in contractile responses before treatment, an effect not seen afterwards in human bladder strips but which persisted in feline bladder strips. Selective alpha-adrenoceptor agonists did not alter the contractile responses in denervated strips. It is suggested that the function of the alpha-adrenoceptors in the detrusor is to inhibit neuronally mediated contractile responses of smooth muscle.

Effect of phenylpropanolamine on incontinence in children with neurogenic bladders. A double-blind crossover study

In children with myelodysplasia and a low-level spinal cord lesion (low lumbar-sacral), detrusor hyperactivity together with dyssynergic urethral function forms the main pathophysiological basis for incontinence. Pharmacological treatment of incontinence due to neurogenic bladder dysfunction has been tried, mainly with anticholinergics and alpha-adrenoceptor antagonists. In this study, the effects of the alpha-adrenoceptor agonist phenylpropanolamine on urodynamic parameters and incontinence were investigated in 10 patients. Effects on incontinence were evaluated in a double-blind crossover trial. Plasma concentrations of phenylpropanolamine were measured by means of gas chromatography-mass spectrometry. Phenylpropanolamine reduced detrusor hyperactivity and improved continence, but the effect was not so pronounced as to make the patients continent.