ABSTRACT
Bladder function is regulated by complex and interrelated neural circuits (Figure 16.1) involving the peripheral and central nervous systems (CNS) (Elbadawi, 1991). The main bladder functions are: (a) urine storage, holding urine at low pressures by relaxing the detrusor muscle and constricting the external urethral sphincter; (b) voiding, releasing urine through contraction of the detrusor muscle and relaxation of the sphincter. These seemingly simple but inter-related functions involve the closely coordinated interactions of the autonomic, sympathetic and somatic divisions of the nervous system. Increasing evidence indicates that, in addition to the classic neurotransmitters acetylcholine (ACh) and norepinephrine (NE), neuropeptides released from the vagus, splanchnic, hypogastric,
Figure 16.1 Diagram depicting neural and neuroimmune bladder circuits. (See Colour Plate I.)
pelvic and pudendal nerves, as well as biogenic amines and cytokines liberated from mast cells, leukocytes and the urothelium profoundly affect bladder function (Kinder and Mundy, 1991). Dysfunction of these interactions could lead to bladder hyperactivity with irritative voiding, urinary incontinence, neuropathic bladder and pelvic pain, symptoms present in conditions such as interstitial cystitis, chronic pelvic pain and non-bacterial prostatitis. Increased bladder permeability could permit penetration of toxic substances through the damaged urothelium and lead to systemic inflammatory symptoms.
