WBR0610

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biochemistry
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A researcher is investigating the regulatory neurotransmitters in the basal ganglia. In his experiment, the researcher sends high frequency electrical impulses into specific areas of the brain of a rat and measures the change in the local concentration of several neurotransmitters. Upon stimulation of the caudate, an increase in the release of a neurotransmitter is detected. The released neurotransmitter is known to inhibit the globus pallidus internus. Which amino acid is the released neurotransmitter derived from?]]
Answer A	AnswerA::Tryptophan
Answer A Explanation	[[AnswerAExp::Tryptophan is not a precursor for GABA.]]
Answer B	AnswerB::Glycine
Answer B Explanation	[[AnswerBExp::Glycine is not a precursor for GABA.]]
Answer C	AnswerC::Glutamate
Answer C Explanation	AnswerCExp::Glutamate is the precursor for GABA, the synthesis of which requires vitamin B6.
Answer D	AnswerD::Arginine
Answer D Explanation	[[AnswerDExp::Arginine is not a precursor for GABA.]]
Answer E	AnswerE::Lysine
Answer E Explanation	[[AnswerEExp::Lysine is not a precursor for GABA.]]
Right Answer	RightAnswer::C
Explanation	[[Explanation::The caudate is involved in the direct and indirect pathways of the fine tuning of motor activity. The caudate is physiologically stimulated by glutamate released from the motor cortex. Stimulation of the caudate, physiologically or experimentally, will likely lead to the release of GABA. GABA is an inhibitory neurotransmitter derived from glutamate. The synthesis of GABA requires vitamin B6. Education objective: GABA is derived from glutamate. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::Basal ganglia, WBRKeyword::GABA, WBRKeyword::glycine
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::