WBR1106

Author	PageAuthor::William J Gibson
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pharmacology
Sub Category	SubCategory::General Principles
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::The alpha2, M2 and D2 receptors are coupled to Gi proteins. The H1 receptor is linked to an intracellular G-protein of the G class.
Answer B	[[AnswerB::Blocks Gq activation]]
Answer B Explanation	[[AnswerBExp::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::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::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::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::