WBR1106
| Author | PageAuthor::William J Gibson |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | |
| Sub Category | |
| Prompt | [[Prompt::A nervous medical student is having a difficult time falling asleep on the night before an important exam. She decides to take an over the counter sleep aid that is also used to reduce allergies. Which of the following most accurately describes the molecular mechanism of this drug?]] |
| Answer A | AnswerA::Blocks Gi activation |
| Answer A Explanation | AnswerAExp::'''Incorrect:''' The alpha2, M2 and D2 receptors are coupled to Gi proteins. The H1 receptor is linked to an intracellular G-protein of the Gq class. |
| Answer B | AnswerB::Blocks Gq activation |
| Answer B Explanation | AnswerBExp::'''Correct:''' Diphenhydramine is a Histamine H1 receptor blocker. The H1 receptor is linked to an intracellular G-protein of the Gq class. |
| Answer C | AnswerC::Blocks Gs activation |
| Answer C Explanation | AnswerCExp::'''Incorrect:''' Beta-adrenergic, H2 and V2 receptor are linked to Gs proteins. However, the H1 receptor is linked to an intracellular G-protein of the Gq class. |
| Answer D | AnswerD::Increases Gi activity |
| Answer D Explanation | AnswerDExp::Incorrect: The alpha2, M2 and D2 receptors are coupled to Gi proteins. The H1 receptor is linked to an intracellular G-protein of the Gq class. |
| Answer E | AnswerE::Increases Gq activity |
| Answer E Explanation | AnswerEExp::'''Incorrect:''' Diphenhydramine blocks the transduction of activating signals from the H1 receptor and thereby blocks rather than increases Gq activity. |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::The patient in this vignette is self-administering diphenhydramine (Benadryl) to help her fall asleep. Diphenyhdramine is a Histamine H1 blocker. The H1 receptor is linked to an intracellular G-protein (Gq) that activates phospholipase C and the phosphatidylinositol (PIP2) signaling pathway. Antihistamines, which act on this receptor, are used as anti-allergy drugs. By blocking histamine binding of the H1 receptor, diphenhydramine blocks Gq activation.
Educational Objective: By blocking histamine binding of the H1 receptor, diphenhydramine blocks Gq activation. References: First aid 2014 page 244 |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Adrenergic, WBRKeyword::Histamine, WBRKeyword::Sleep |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |