Figure 8.3. Deadly nightshade, Atropa belladonna.In addition to slowing intestinal motility and dilating the pupil
of the eye, the other parasympatholytic effects of atropine include
increased heart rate, dilation of the lung airways, dry mouth, and
difficulty urinating. Collectively, these effects of blocking parasym-
pathetic neural activity are often called anticholinergic effects. In
addition, blocking mAChRs at the heart may produce heartbeat irreg-
ularities, which can be fatal—hence the deadly poisonous aspect of at-
ropine and its mother plant Atropa belladonna.
Atropine crosses the blood-brain barrier and there are many
mAChRs in the brain. Thus, atropine has psychoactive effects, and
these CNS effects may be very strong. Among these effects are alter-
ations of consciousness that may be dreamy and hallucinatory. A