Q: Which equation describes the current through a ligand-gated ion channel, and what does each variable represent?

$$I_n = g_n \times (V_m - V_n)$$, where $$I_n is $$the current, $$g_n is $$the channel conductance, $$V_m is $$membrane voltage, and $$V_n is $$the equilibrium potential for the ion.

Question 1

Which of the following best explains why ligand-gated ion channel (LGIC) currents are transient, even when the ligand remains present at the synapse?

Accepted Answer

Desensitization occurs, causing the channel to close despite continued ligand binding.

Question 2

A mutation causes a cys-loop receptor to become permeable to cations instead of anions. What is the most likely effect on neuronal signaling?

Accepted Answer

The receptor will now mediate excitatory postsynaptic potentials (EPSPs).

Question 3

Which equation describes the current through a ligand-gated ion channel, and what does each variable represent?

Accepted Answer

$$I_n = g_n 	imes (V_m - V_n)$$, where $$I_n is $$the current, $$g_n is $$the channel conductance, $$V_m is $$membrane voltage, and $$V_n is $$the equilibrium potential for the ion.

Question 4

Which of the following drugs acts as a positive allosteric modulator (PAM) of GABA$$_A$$ receptors?

Accepted Answer

Barbiturates

Question 5

Which structural feature defines cys-loop receptors?

Accepted Answer

A pentameric assembly with four transmembrane segments per subunit and an extracellular cys-loop on the N-terminus.

Question 6

Which of the following is required for NMDA receptor activation?

Accepted Answer

Binding of glutamate and either D-serine or glycine, plus depolarization to remove Mg$$^{2+}$$ block.

Question 7

Which ions are permeable through NMDA receptors?

Accepted Answer

K$$^+$$, Na$$^+$$, and Ca$$^{2+}$$

Question 8

A drug that blocks AMPA receptors would most likely have which effect on NMDA receptor activation?

Accepted Answer

It would decrease NMDA receptor activation by preventing depolarization needed to remove Mg$$^{2+}$$ block.

Question 9

Which of the following best describes the pharmacological targeting of ligand-gated ion channels?

Accepted Answer

Drugs can act as agonists, antagonists, or allosteric modulators at LGICs.

Question 10

Which of the following is a function of P2X purinergic receptors?

Accepted Answer

Regulating nociception and chronic pain

Question 11

Which of the following statements about AMPA and Kainate receptors is correct?

Accepted Answer

Both are glutamatergic LGICs with rapid desensitization kinetics and are permeable to cations.

Question 12

Which of the following would impair the coincident detection of pre- and post-synaptic activity via NMDA receptor activation?

Accepted Answer

All of the above

Question 13

Which of the following is the endogenous ligand for P2X purinergic receptors?

Accepted Answer

ATP

Question 14

Which structural domain of glutamate receptors contains the orthosteric binding site for glutamate?

Accepted Answer

Ligand binding domain (LBD)

Question 15

Which of the following best describes the voltage-dependent behavior of NMDA receptors?

Accepted Answer

Mg$$^{2+}$$ blocks the channel at negative voltages and is removed by depolarization.

Question 16

Which of the following is a major function of AMPA receptors in the CNS?

Accepted Answer

Mediating fast excitatory neurotransmission and synaptic plasticity

Question 17

Which of the following statements about acid-sensing ion channels (ASICs) is correct?

Accepted Answer

ASICs are activated by H$$^+$$ and contribute to pain perception during tissue acidosis.

Question 18

Which of the following would increase sensitivity to bitter flavors via P2X receptors?

Accepted Answer

A mutation that increases expression of P2X channels in the membrane

Question 19

Which of the following best describes the structure of P2X family receptors?

Accepted Answer

Trimeric channels with two transmembrane segments per subunit

Ligand-Gated Ion Channels 2

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