Which of the following cholinergic effects is beneficial in treating urinary retention?

Increased bladder tone is beneficial in treating urinary retention because it enhances the contractility of the bladder muscles, allowing for more effective emptying of the bladder. Cholinergic agents work by activating the parasympathetic nervous system, which stimulates the detrusor muscle in the bladder. This action improves the ability of the bladder to contract and push urine out, relieving the retention.

By increasing the tone of the bladder, cholinergic medications help coordinate urination by ensuring that the muscle is engaged properly during the micturition reflex. In conditions like urinary retention, where the bladder may not be emptying effectively, this effect is crucial.

In contrast, decreased bladder tone or decreased urine output would exacerbate urinary retention rather than alleviate it, as they do not facilitate the contraction of the bladder muscle necessary for proper urination. Increased urine output does not specifically address the retention issue but rather describes a separate function of renal activity. Thus, increased bladder tone is the key factor in improving urinary function in the context of urinary retention.