Cyclothiazide MCQs With Answer

Cyclothiazide is a benzothiadiazide derivative widely discussed in pharmacology for its unique modulation of glutamatergic signaling. Unlike classic thiazide diuretics, cyclothiazide acts as a positive allosteric modulator of AMPA receptors by inhibiting receptor desensitization, thereby enhancing excitatory synaptic currents. Its mechanism of action, receptor selectivity, pharmacokinetics, adverse effects (including pro‑convulsant risk), and drug interactions make it a valuable topic for B. Pharm students studying neuropharmacology and receptor modulation. Although mainly an experimental tool rather than a routine therapeutic agent, understanding cyclothiazide deepens insight into excitatory neurotransmission, toxicology and research applications. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the primary pharmacological action of cyclothiazide on glutamate receptors?

• Competitive antagonism at NMDA receptors
• Positive allosteric modulation of AMPA receptors by inhibiting desensitization
• Direct agonism of metabotropic glutamate receptors
• Irreversible blockade of kainate receptors

Correct Answer: Positive allosteric modulation of AMPA receptors by inhibiting desensitization

Q2. Cyclothiazide is chemically classified as which of the following?

• Beta‑lactam antibiotic
• Benzothiadiazide derivative
• Catecholamine
• Peptide neurotransmitter

Correct Answer: Benzothiadiazide derivative

Q3. In electrophysiological studies, cyclothiazide is most commonly used to:

• Enhance GABAergic inhibitory postsynaptic currents
• Prevent AMPA receptor desensitization to study sustained currents
• Block voltage‑gated sodium channels
• Activate muscarinic receptors

Correct Answer: Prevent AMPA receptor desensitization to study sustained currents

Q4. A known adverse effect of cyclothiazide relevant to its excitatory action is:

• Severe bradycardia
• Pro‑convulsant activity and increased seizure risk
• Profound sedation and respiratory depression
• Autoimmune hemolytic anemia

Correct Answer: Pro‑convulsant activity and increased seizure risk

Q5. Which statement about clinical therapeutic use of cyclothiazide is correct?

• It is a first‑line antihypertensive used worldwide
• It has well‑established clinical dosing guidelines for epilepsy
• It is primarily a research tool with limited therapeutic application
• It is the preferred diuretic in heart failure

Correct Answer: It is primarily a research tool with limited therapeutic application

Q6. Cyclothiazide enhances AMPA receptor currents mainly by:

• Increasing receptor expression at the membrane within minutes
• Blocking AMPA receptor pore conductance
• Slowing or preventing receptor desensitization during sustained glutamate exposure
• Facilitating endocytosis of AMPA receptors

Correct Answer: Slowing or preventing receptor desensitization during sustained glutamate exposure

Q7. Which receptor subunits are the primary molecular targets for cyclothiazide modulation?

• GluA (AMPA) receptor subunits
• GluN (NMDA) receptor subunits
• mGluR Group II subunits
• GABA_B receptor subunits

Correct Answer: GluA (AMPA) receptor subunits

Q8. Regarding cyclothiazide’s interaction with GABAergic transmission, evidence suggests it may:

• Potentiate GABA_A receptor currents strongly
• Have no effect on GABAergic signaling
• Antagonize GABA_A receptor function and reduce inhibition
• Act as an agonist at GABA_B receptors

Correct Answer: Antagonize GABA_A receptor function and reduce inhibition

Q9. Which experimental outcome is expected when cyclothiazide is applied during synaptic recordings of excitatory postsynaptic currents (EPSCs)?

• EPSC amplitude decreases and decay is faster
• EPSC amplitude increases and decay is prolonged
• No change in EPSC but increased inhibitory postsynaptic potentials
• Complete blockade of all synaptic currents

Correct Answer: EPSC amplitude increases and decay is prolonged

Q10. Cyclothiazide’s pro‑convulsant risk is primarily due to:

• Excessive enhancement of inhibitory tone in cortical circuits
• Activation of voltage‑gated potassium channels
• Enhanced excitatory glutamatergic transmission via AMPA receptors
• Direct mitochondrial toxicity in neurons

Correct Answer: Enhanced excitatory glutamatergic transmission via AMPA receptors

Q11. Which precaution is most relevant when using cyclothiazide in animal research?

• Monitor for signs of respiratory depression due to opioid‑like effects
• Avoid combining with NMDA agonists because they neutralize its action
• Be cautious of seizure induction and provide anticonvulsant readiness
• No special precautions are required; it is inert in vivo

Correct Answer: Be cautious of seizure induction and provide anticonvulsant readiness

Q12. In drug interaction terms, combining cyclothiazide with which class could theoretically reduce its pro‑convulsant effects?

• Benzodiazepines that enhance GABA_A receptor activity
• Potent AMPA receptor positive modulators
• Tricyclic antidepressants that increase glutamate release
• Stimulants that increase excitatory neurotransmission

Correct Answer: Benzodiazepines that enhance GABA_A receptor activity

Q13. Which assay would most directly demonstrate cyclothiazide’s effect on AMPA receptor desensitization?

• Patch‑clamp recording of AMPA receptor currents in cultured neurons
• ELISA measurement of serum electrolyte levels
• Behavioral open field test for anxiety
• Western blot for actin levels

Correct Answer: Patch‑clamp recording of AMPA receptor currents in cultured neurons

Q14. Structurally, cyclothiazide is most closely related to which therapeutic class?

• Thiazide diuretics
• Beta blockers
• SSRIs (selective serotonin reuptake inhibitors)
• Statins

Correct Answer: Thiazide diuretics

Q15. Which statement about cyclothiazide pharmacokinetics is accurate?

• It has an established oral dosing schedule in humans
• Comprehensive human pharmacokinetic data are limited; most data are preclinical
• It is rapidly metabolized into an active NMDA antagonist
• It is exclusively eliminated via pulmonary exhalation

Correct Answer: Comprehensive human pharmacokinetic data are limited; most data are preclinical

Q16. Cyclothiazide’s effect on synaptic plasticity studies is important because it:

• Induces long‑term depression (LTD) by blocking AMPA receptors
• Can artificially maintain AMPA receptor currents and affect LTP/LTD measurements
• Specifically blocks protein synthesis required for plasticity
• Prevents calcium entry through NMDA receptors directly

Correct Answer: Can artificially maintain AMPA receptor currents and affect LTP/LTD measurements

Q17. Which of the following experimental controls is important when using cyclothiazide to study AMPA responses?

• Include a GABA_B receptor antagonist as the only control
• Use AMPA receptor antagonists (e.g., CNQX) to confirm specificity
• Assume any change is due to NMDA receptor modulation without testing
• No controls are necessary when using cyclothiazide

Correct Answer: Use AMPA receptor antagonists (e.g., CNQX) to confirm specificity

Q18. Which experimental observation would suggest off‑target effects of cyclothiazide?

• Selective increase of AMPA currents reversed by CNQX
• Altered intracellular chloride leading to changed GABA responses
• No change in neuronal excitability despite drug application
• Reproducible enhancement of AMPA currents in multiple preparations

Correct Answer: Altered intracellular chloride leading to changed GABA responses

Q19. When interpreting data obtained with cyclothiazide, students must remember that:

• Its effects strictly mimic physiological synaptic transmission
• It eliminates the need for receptor antagonists in experiments
• It can exaggerate excitatory signaling and confound physiological interpretations
• It is a neutral compound that stabilizes baseline currents

Correct Answer: It can exaggerate excitatory signaling and confound physiological interpretations

Q20. Which is a commonly reported cellular consequence of prolonged cyclothiazide exposure in neurons?

• Reduced intracellular calcium levels and neuroprotection
• Excitotoxic neuronal injury due to sustained AMPA activation
• Complete shutdown of glutamate release
• Enhanced oligodendrocyte proliferation

Correct Answer: Excitotoxic neuronal injury due to sustained AMPA activation

Q21. Which experimental combination would most likely exacerbate cyclothiazide‑induced excitotoxicity?

• Co‑application with AMPA receptor antagonists
• Co‑application with glutamate or an AMPA agonist
• Treatment with GABA_A positive modulators
• Reduction of extracellular glutamate concentration

Correct Answer: Co‑application with glutamate or an AMPA agonist

Q22. For a student designing an in vitro experiment, which solvent consideration is relevant for cyclothiazide?

• It is highly water‑soluble and requires no co‑solvent
• Often dissolved in DMSO or ethanol as stock before dilution due to limited aqueous solubility
• Must be dissolved in strong acid to be active
• Only gaseous formulations are active in vitro

Correct Answer: Often dissolved in DMSO or ethanol as stock before dilution due to limited aqueous solubility

Q23. Which experimental readout would best indicate that cyclothiazide is preserving AMPA receptor open states?

• Decreased single‑channel open time in patch‑clamp recordings
• Increased single‑channel open probability and prolonged burst durations
• Reduced frequency of spontaneous synaptic events only
• Selective inhibition of postsynaptic GABA currents

Correct Answer: Increased single‑channel open probability and prolonged burst durations

Q24. Which statement about cyclothiazide and NMDA receptors is most accurate?

• Cyclothiazide is a potent NMDA receptor agonist
• Cyclothiazide directly blocks NMDA receptor channels at therapeutic concentrations
• Its primary action is on AMPA receptors; NMDA effects are indirect or minimal
• It is a selective NMDA receptor antagonist used clinically

Correct Answer: Its primary action is on AMPA receptors; NMDA effects are indirect or minimal

Q25. Which laboratory safety consideration is important when handling cyclothiazide?

• No special PPE is required because it is non‑toxic
• Use of gloves and eye protection, and minimizing aerosolization, due to neuroactive properties
• Only thermal hazards are relevant during handling
• It must be handled in a biosafety cabinet as a live pathogen

Correct Answer: Use of gloves and eye protection, and minimizing aerosolization, due to neuroactive properties

Q26. In comparing cyclothiazide to classical thiazide diuretics, which is true?

• Cyclothiazide is widely used as an antihypertensive like hydrochlorothiazide
• Both share a chemical scaffold, but cyclothiazide’s dominant research interest is neuropharmacology, not diuresis
• Cyclothiazide has identical renal mechanisms and clinical indications
• Cyclothiazide is a loop diuretic, not related to thiazides

Correct Answer: Both share a chemical scaffold, but cyclothiazide’s dominant research interest is neuropharmacology, not diuresis

Q27. Which experimental control helps determine whether cyclothiazide effects are receptor‑mediated rather than nonspecific?

• Using heat inactivation of the preparation before application
• Co‑application of a selective AMPA antagonist to reverse effects
• Assuming receptor mediation without antagonists
• Measuring only gross behavioral outcomes

Correct Answer: Co‑application of a selective AMPA antagonist to reverse effects

Q28. A pharmacology student asks why cyclothiazide can be confusing in synaptic studies. The best explanation is:

• It exclusively affects presynaptic neurotransmitter release, which is easy to measure
• It enhances postsynaptic AMPA currents and can mask physiological desensitization, altering synaptic dynamics
• It is rapidly degraded in all experimental buffers
• It has no effect on synaptic transmission under any conditions

Correct Answer: It enhances postsynaptic AMPA currents and can mask physiological desensitization, altering synaptic dynamics

Q29. Which clinical implication should students remember about cyclothiazide research findings?

• All findings directly translate to safe human therapeutics without further study
• Research insights into AMPA modulation can inform drug discovery, but safety and translational hurdles remain
• Cyclothiazide is approved for routine clinical use in neurodegenerative diseases
• Its excitatory actions guarantee clinical benefit in cognitive disorders

Correct Answer: Research insights into AMPA modulation can inform drug discovery, but safety and translational hurdles remain

Q30. For exam preparation, which core concept about cyclothiazide should B. Pharm students prioritize?

• Its role as a broad‑spectrum antibiotic
• Its positive allosteric modulation of AMPA receptors and implications for excitatory neurotransmission and toxicity
• Its exclusive use as a cardiovascular diagnostic agent
• Its function as an opioid receptor antagonist

Correct Answer: Its positive allosteric modulation of AMPA receptors and implications for excitatory neurotransmission and toxicity

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