Mp08-10 lateralization of Bladder Function in Normal Female Canines

Abstract

INTRODUCTION AND OBJECTIVE: This study determined the effect of pelvic organ long-term decentralization and reinnervation one year later on the contribution of muscarinic and purinergic receptors to ex-vivo, nerve-evoked, bladder smooth muscle contractions.METHODS: Nineteen canines underwent decentralization by bilateral transection of all coccygeal and sacral (S) spinal roots, dorsal roots of lumbar (L)7 and hypogastric nerves. After exclusions, 8 were reinnervated 12 months post-decentralization with obturator-to-pelvic and sciatic-to-pudendal nerve transfers then euthanized 8-12 months later; four served as long-term decentralized only animals. Controls included six sham-operated and three unoperated animals. Bladder tissues were assessed for contractile responses to potassium chloride (KCl) and electric field stimulation (EFS) before and after purinergic receptor desensitization with alpha, beta-methylene adenosine triphosphate (a,b-mATP), muscarinic receptor antagonism with atropine, or sodium channel blockade with tetrodotoxin.RESULTS: Atropine inhibition of EFS-induced contractions increased by 26%in decentralized and 34%in the reinnervated animals compared to controls. Maximal contractile responses to a,b-mATP did not differ between groups. In strips from decentralized and reinnervated animals, the contractile response to EFS was enhanced by 52% at lower frequencies and the response to KCl was increased compared to normal controls.CONCLUSIONS: The observation of increased blockade of nerve-evoked contractions by muscarinic antagonist with no change in responsiveness to purinergic agonist suggests either decreased ATP release or increased ectoATPase activity in detrusor muscle as a consequence of the long-term decentralization. The reduction in the frequency required to produce maximum contraction following decentralization may be due to enhanced nerve sensitivity to EFS or a change in the effectiveness of the neurotransmission.