American Board of Psychiatry and Neurology (ABPN) Practice Exam 2026 - Free ABPN Practice Questions and Study Guide

The H1 receptor is particularly associated with weight gain and sedation due to its role in mediating the effects of histamine in the central nervous system. Antihistaminergic effects, which block H1 receptors, are often linked to increased appetite and drowsiness. Many medications that cause sedation also exhibit antihistamine properties, which contribute to these effects.

Histamine in the brain plays a critical role in regulating wakefulness and arousal; thus, blocking H1 receptors can lead to sedation and increased lethargy. The stimulation of these receptors can promote alertness and energy, while their blockade results in reduced activity and increased appetite, often leading to weight gain over time. This mechanism is particularly evident with certain antipsychotic medications and sedatives that function as H1 antagonists, highlighting their connection to these side effects.

Other receptor types, such as 5-HT 1A, α1, and 5-HT 2A, have different functions and are less directly associated with weight gain and sedation specifically, making the H1 receptor the most relevant in this context.