Purinergic and cholinergic components of bladder contractility and flow

Area of Science:

• Urology
• Neuroscience
• Pharmacology

Background:

• The role of adenosine triphosphate (ATP) as a neurotransmitter in the urinary tract is debated.
• Species-specific variations in ATP's function, particularly in cats, require further investigation.
• Understanding ATP's role is crucial for elucidating mechanisms of urine flow and bladder function.

Purpose of the Study:

• To investigate the in vivo response of the cat urinary bladder to pelvic nerve stimulation (PNS) and exogenous cholinergic and purinergic agents.
• To differentiate the functional roles of ATP and acetylcholine (ACh) in feline lower urinary tract activity.
• To determine if ATP contributes to urine flow initiation in cats.

Main Methods:

• Anesthetized cats underwent measurement of bladder contractions and fluid expulsion.
• Responses were recorded following pelvic nerve stimulation (PNS) and administration of carbachol, ATP, and acetylcholine (ACh).
• The effects of atropine, a cholinergic antagonist, were assessed on PNS-induced responses.

Main Results:

• PNS, carbachol, and the ATP analog (APPCP) induced sustained bladder contractions and significant fluid expulsion.
• ATP, ACh, and hypogastric nerve stimulation did not result in significant fluid expulsion.
• Atropine blocked PNS-induced contractions and fluid expulsion but did not affect purinergic responses.
• A strong correlation was observed between contraction magnitude/duration and fluid volume expelled.

Conclusions:

• ATP functions as a cotransmitter in the feline lower urinary tract with a role distinct from ACh.
• ATP stimulation of purinergic receptors initiates bladder contractions and may initiate urine flow.
• Acetylcholine (ACh) appears primarily involved in maintaining contractile activity and flow, rather than initiation.