Which of the following symptoms would likely indicate a cholinergic effect?

The presence of increased salivation is indicative of a cholinergic effect, which is associated with the stimulation of the parasympathetic nervous system. Cholinergic agents, such as acetylcholine, promote bodily functions that are relaxed and restorative, often leading to secretions that aid digestion and other processes. This increase in salivation occurs because cholinergic stimulation enhances the activation of salivary glands, leading to the production and secretion of saliva.

In contrast, the other symptoms listed reflect anticholinergic effects or a decrease in parasympathetic activity. For instance, dry mouth is typically a result of reduced salivary production, which aligns with decreased cholinergic activity. Constipation may arise when there is a decrease in gastrointestinal motility, often caused by insufficient cholinergic stimulation. Increased heart rate is indicative of sympathetic nervous system activity, rather than parasympathetic, which would generally result in a decreased heart rate through cholinergic stimulation. Therefore, increased salivation stands out as a clear cholinergic effect, confirming the correctness of the chosen answer.