Figure II-2-2. Continence and Micturitionstimulated cause contraction of urethral smooth muscle, preventing
micturition. Drugs: ephedrine, imipramine, and estrogens. α-adrenergic
blockers or antagonists relax the urethra, enhancing micturition. Drugs:
phenoxybenzamine.
β-adrenergic receptors are found primarily in the detrusor muscle and when
stimulated cause relaxation of the bladder wall, preventing micturition. Drugs:
flavoxate and progestins.
Cholinergic receptors are found primarily in the detrusor muscle and when
stimulated cause contraction of the bladder wall, enhancing micturition.
Drugs: bethanechol and neostigmine. Anticholinergic medications block the
receptors, inhibiting micturition. Drugs: oxybutynin and propantheline.