Neuropeptide/Receptor Expression and Plasticity in Micturition Pathways

Several motor behaviors such as locomotion, respiration, sexual function, and micturition are generated by rhythmic and stereotyped motor patterns of activity. In most cases, these functions are primarily controlled by signals and neuronal commands that originate from the brainstem and spinal cord. Defined as the storage and periodic elimination of urine, micturition requires a complex neural control system that coordinates the activities of a variety of effector organs including the smooth muscle of the urinary bladder and the smooth and striated muscle of the urethral sphincters. The lower urinary tract (LUT) reflex mechanisms, organized at the level of the lumbosacral spinal cord, are modulated predominantly by supraspinal controls. These LUT mechanisms include: (1) storage reflexes organized at the spinal level; (2) elimination reflexes organized at a supraspinal site in the pons; and (3) spinal storage reflexes modulated by inputs from the rostral pons. Precise coordination of the reciprocal functions of the urinary bladder and urethra and complex neural organization are required for normal function. Numerous neuropeptide/receptor systems are expressed in central and peripheral nervous system pathways that regulate the LUT and expression can also be found in both neural and non-neural (e.g., urothelium) components. Neuropeptides have tissue-specific distributions and functions in the LUT and exhibit neuroplastic changes in expression and function with LUT dysfunction with neural injury, inflammation, stress and disease. LUT dysfunction with abnormal voiding including urinary urgency, increased voiding frequency, nocturia, urinary incontinence, urinary retention, continence, detrusor dysynergia and/or pain may reflect a change in the balance of neuropeptides in central and peripheral bladder reflex pathways. LUT neuropeptide/receptor systems in LUT pathways may thus represent potential targets for therapeutic intervention.