CONTROL OF DETRUSOR STIFFNESS IN THE CHRONIC DECENTRALIZED FELINE BLADDER

The neuropharmacology of increased bladder stiffness, which may contri bute to upper tract damage and incontinence, was investigated in 76 ca ts. Beta-blockade increased but combined alpha1-adrenergic with muscar inic blockade decreased filling phase stiffness in normal cats. Bladde r wall stiffness during the early filling phase was unaffected by chro nic S2 ventrodorsal rhizotomy or L7-S3 ventral rhizotomy, but was decr eased when L7-S3 dorsal rhizotomy or total sympathectomy was combined with the ventral root lesion, implying that sacral dorsal roots and sy mpathetic efferents maintain normal detrusor stiffness. Acute sympathe ctomy increased stiffness in all the former 3 chronic groups, implying that a tonic or reflex sympathetic inhibition operates independently of the L7-S3 dorsal roots. Stiffness during early filling phase decrea sed with acute ventral rhizotomy. This change persisted with chronic s ympathectomy but returned to normal if sympathetic nerves were left in tact. These results suggest that bladder stiffness is modulated by ton ic or reflexic sympathetic activity, which is influenced by L7-S3 affe rents. Detrusor stiffness during the later stages of filling, which wa s decreased by acute sympathectomy in chronic groups but increased by chronic sympathectomy, was reduced by interference with adrenergic or muscarinic mechanisms after either lesion. Therefore, a peripheral pat hway with facilitatory alpha1-adrenergic and muscarinic receptors is i nvolved in the production of increased late stage stiffness after chro nic sympathetic damage. We propose that the increased bladder stiffnes s seen in congenital sacral lesions may be analogous to the stiffness during late stages of filling reported here. Our results also imply th at the presence of this increased stiffness is closely associated with chronic sympathetic damage. Whether the increased stiffness in congen ital and traumatic neural lesions in humans arises from sympathetic da mage remains to be determined.