Nerve agents are known to cause all the following symptoms EXCEPT?

The symptoms associated with nerve agent exposure are primarily due to the disruption of the normal functioning of the nervous system, particularly through inhibition of the enzyme acetylcholinesterase. This inhibition leads to a buildup of acetylcholine, which causes overstimulation of the neurons.

Increased saliva production occurs because the buildup of acetylcholine stimulates the salivary glands, leading to excessive salivation. Constriction of pupils, or miosis, is another symptom that results from overstimulation of the muscles controlling the iris. Muscle twitching also happens as a result of sustained muscular contraction from the constant stimulation by acetylcholine.

In contrast, a slow heart rate, known as bradycardia, is not a typical direct effect of nerve agents. In fact, nerve agents usually cause increased heart rates initially due to the sympathetic nervous system's response. While there may be cardiovascular complications in severe cases or secondary effects, it is not a hallmark symptom caused directly by nerve agents like the other listed symptoms. Thus, the correct answer reflects a misunderstanding of the primary physiological effects of nerve agents.