Interaction between adrenergic and cholinergic nerve terminals in the urinary bladder of rabbit, cat and man

The influence of muscarinic receptor stimulation (carbachol) and blockade (scopolamine) on the release of 3H-labelled noradrenaline from adrenergic neurons was investigated in isolated detrusor preparations from rabbit, cat and man. A significant influence on the release of 3H from adrenergic nerve terminals was found in the three species with a concentration-dependent decrease and increase induced by carbachol and scopolamine, respectively. Using the alpha 2-adrenoceptor stimulating and blocking agents clonidine and rauwolscine in rabbit and human detrusor preparations, the presence of prejunctionally located inhibitory alpha 2-adrenoceptors could also be demonstrated. The findings indicate the possibility of a functionally important interaction between cholinergic and adrenergic nerves in the urinary bladder mediated via inhibitory muscarinic receptors on adrenergic nerve terminals.