Neural control of the urethra

Area of Science:

• Neuroscience
• Urology
• Physiology

Background:

• The urinary bladder and urethra coordinate through complex reflex pathways in the central and peripheral nervous systems.
• These reflexes are crucial for maintaining urinary continence, involving both urine storage and voiding functions.

Purpose of the Study:

• To elucidate the neural mechanisms governing the coordination between the urinary bladder and urethra.
• To investigate the roles of various neurotransmitters and spinal circuitry in micturition reflexes.

Main Methods:

• The study examines the reflex pathways involved in bladder storage and voiding.
• It discusses the roles of cholinergic, adrenergic, glutamatergic, serotonergic, GABAergic, and nitrergic transmissions.
• Neural circuitry in the spinal cord and supraspinal control from the pontine micturition center are considered.

Main Results:

• Spinal cord interneuronal circuitry mediates storage reflexes involving the external urethral sphincter (EUS) and urethral smooth muscle.
• Supraspinal mechanisms from the pontine micturition center inhibit spinal storage reflexes during voiding.
• A parasympathetic nitrergic inhibitory input to the urethral smooth muscle is activated during voiding, persisting in paraplegic rats.
• Sex differences exist, with a prominent nitrergic pathway in females and a dominant cholinergic excitatory input in males.

Conclusions:

• The bladder and urethra utilize intricate reflex mechanisms for coordinated function.
• Spinal interneuronal circuitry plays a significant role in both storage and voiding reflexes.
• Dysfunction in these primitive reflex mechanisms may lead to neurogenic bladder disorders.