AIIMS Raipur - 2017 (shift-2)
Pharmacology
Easy
Which among the following is an excitatory amino acid receptor antagonist?
Appeared in: AIIMS Raipur - 2017 (shift-2)
Explanation
- The question asks to identify an antagonist for excitatory amino acid (EAA) receptors.
- EAA receptors, primarily glutamate receptors, include NMDA, AMPA, and Kainate subtypes.
- Phencyclidine (PCP) is a well-known non-competitive antagonist that acts by blocking the ion channel of the NMDA receptor.
- By blocking the NMDA receptor, phencyclidine prevents the excitatory effects of glutamate, classifying it as an EAA receptor antagonist.
Why Other Options Were Wrong
- Option B: Quisqualate is an agonist, not an antagonist. It activates AMPA receptors, a type of EAA receptor, causing excitation.
- Option C: Homocysteate is an agonist that activates NMDA receptors, leading to an excitatory response.
- Option D: Kainite (or Kainate/Kainic acid) is the specific agonist used to identify and characterize Kainate receptors. It causes excitation, so it is not an antagonist.
Related Visual
Clinical Relevance
- Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pharmacology of Excitatory Amino Acid (EAA) Receptors as background academic context rather than a clinical decision trigger.
- Understanding EAA receptor pharmacology is crucial as these receptors are targets for various drugs.
- NMDA receptor antagonists have significant clinical applications. For example, Ketamine, which is structurally similar to phencyclidine, is used as a dissociative anesthetic. Memantine, another NMDA antagonist, is used to treat moderate-to-severe Alzheimer's disease.
- Overstimulation of EAA receptors (excitotoxicity) is implicated in neuronal damage following stroke, traumatic brain injury, and in neurodegenerative diseases like Huntington's disease. Research is ongoing to develop antagonists to mitigate this damage.
How to Approach the Question
- First, identify the core concepts in the question: 'excitatory amino acid (EAA) receptor' and 'antagonist'.
- Recall that the main EAA neurotransmitter is glutamate, and its primary ionotropic receptors are NMDA, AMPA, and Kainate.
- Differentiate between an 'agonist' (activates a receptor) and an 'antagonist' (blocks a receptor).
- Evaluate each option based on its known pharmacological action.
- Recall or deduce that Phencyclidine blocks NMDA receptors, making it an antagonist.
- Recognize that Quisqualate, Homocysteate, and Kainite are all substances that activate (are agonists for) different EAA receptors.
Concept Tested & Keywords
- Concept Tested: Pharmacology of Excitatory Amino Acid (EAA) Receptors
- Stem keywords: excitatory amino acid, receptor antagonist
- Lead-in keywords: Which among the following
Question ID
Qm7FdXQFYsdkbS3dERbPVk
Reference Book
E6 Robert Boland, Marcia L. Verduin - Kaplan and Sadock's Comprehensive Text of Psychiatry-Wolters Kluwer Health (2024) (pp 1-16525 of 16525) p. 409-411
E6 Pharmacology Katzung 16e p. 587-589
Practise the full AIIMS Raipur - 2017 (shift-2)
Attempt every question from this paper in a timed mock, then review the full solution for each one.
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