EFFECTS OF PARASYMPATHETIC DECENTRALIZATION ON SOME NERVE-MEDIATED FUNCTIONS IN THE FELINE URINARY-BLADDER

Isolated detrusor muscle from control cats and cats parasympathetically decentralized for 3 and 10 weeks responded to electrical field stimulation by tetrodotoxin-sensitive, frequency-dependent contractions. There were no significant differences in the frequencies producing 50% response. However, the amplitude of the scopolamine-resistant contraction was distinctly lower in decentralized bladder preparations than in controls. Decentralized detrusor muscle (10 weeks) showed no increased response to alpha-adrenoceptor stimulation (phenylephrine, clonidine, noradrenaline), but the sensitivity to carbachol (at 3 and 10 weeks) was significantly decreased compared with controls. The release of [H-3]noradrenaline was decreased by carbachol 10(-7) 10(-5) M both in controls and in decentralized (10 weeks) detrusor muscle, the decrease being significantly more pronounced in the decentralized group at carbachol concentrations of 10(-7) and 10(-6) M. There were no differences between controls and decentralized bladders of muscarinic receptor concentration, but decentralization significantly reduced the affinity for the radioligand used to label the receptors. Thus, the main changes caused by parasympathetic decentralization of the feline bladder seem to be a reduced post-junctional, but an increased prejunctional response to muscarinic receptor stimulation.