Neural control of the urethra and development of pharmacotherapy for stress urinary incontinence

This review discusses the control of the urethra by the central nervous system, emphasizing the importance of nervous system control and the role of serotonin and noradrenaline in storage, micturition and sphincter reflexes. The concept of pharmacological neuromodulation and the use of pharmacological therapy as first-line therapy for stress urinary incontinence (SUI) is presented. Coordination between the urinary bladder and urethra is mediated by many reflex pathways organized in the brain and spinal cord. During bladder filling, activation of mechanoreceptor afferent nerves in the bladder wall triggers firing in the cholinergic efferent pathways to the external urethral sphincter and in sympathetic adrenergic pathways to the urethral smooth muscle. These storage reflexes depend on interneuronal circuitry in the spinal cord and are modulated by descending pathways. It would therefore seem that neurotransmission in the central nervous system and periphery may be important in SUI, and moreover that pharmacological agents affecting these neurotransmitter pathways may be used to treat SUI. The central and peripheral mechanisms of action of duloxetine affect serotonin and noradrenaline neurotransmission in ways that may ameliorate the symptoms of SUI.