Final answer:
Nicotine's pharmacologic effects at low doses include complex interactions with GI and cardiovascular systems, primarily through acetylcholine receptor stimulation that can lead to increased blood pressure and heart arrhythmias.
Step-by-step explanation:
Understanding the pharmacologic effects of nicotine, particularly at low doses, reveals its complex impact on the gastrointestinal (GI) system. Nicotine's interaction with acetylcholine receptors can produce a stimulant effect, although this is often transient and followed by depression. Because nicotine primarily stimulates sympathetic and parasympathetic ganglia at the preganglionic fiber synapse, this can lead to an increase in blood pressure and potential arrhythmias, which are risk factors for cardiovascular disease.
Furthermore, nicotine replacement therapies such as patches, gums, and lozenges aim to mitigate withdrawal symptoms and facilitate smoking cessation, although a high relapse rate is reported within 12 months of therapy.