Blocking the action of which neurotransmitter is often the desired effect of certain "blocker" drugs?

Blocking the action of acetylcholine is often the desired effect of certain "blocker" drugs, particularly in therapeutic contexts where the modulation of parasympathetic nervous system activity is beneficial. Acetylcholine is the primary neurotransmitter involved in transmitting impulses in the parasympathetic nervous system, affecting functions such as heart rate, glandular secretions, and smooth muscle contraction.

Drugs that block acetylcholine receptors, known as anticholinergics, are used to reduce muscle spasms, decrease secretions in conditions like asthma, and manage symptoms of motion sickness, among other uses. By inhibiting the action of acetylcholine, these drugs can produce effects such as decreased salivation and bronchial secretions, reduced gastrointestinal motility, and relaxation of smooth muscles.

This modulation is particularly important in certain medical treatments, such as in the management of overactive bladder, chronic obstructive pulmonary disease (COPD), and as part of anesthesia protocols. Therefore, the focus on acetylcholine in this context underscores its critical role in numerous physiological processes that can be altered for therapeutic benefit through "blocker" drugs.