Drugs like diazepam (Valium), a benzodiazepine, exert their action on ion channels. These drugs do not open the GABA-operated ion channel, but they:

Question

A) Modulate the release from axon terminals
B) Modulate the peripheral sympathetic nerves and can have both a transmitter and modulator function
C) Change the effect that GABA has when it binds to the channel at the same time as the drug
D) Play a necessary role in the long-term survival of presynaptic neurons

Answer 1

Ans: C
Feedback:
Amino acids, such as glutamine, glycine, and GABA, serve as neurotransmitters at most CNS synapses. GABA mediates most synaptic inhibition in the CNS. Drugs such as the benzodiazepines (e.g., the tranquilizer diazepam) and the barbiturates exert their action by binding to their own distinct receptor on a GABA-operated ion channel. The drugs by themselves do not open the channel, but they change the effect that GABA has when it binds to the channel at the same time as the drug. Another class of messenger molecules, known as neuromodulators, also may be released from axon terminals. In contrast to neurotransmitters, neuromodulators do not directly activate ion channel receptors but bring about long-term changes that subtly enhance or depress the action of the receptors. Neuromodulators, such as dopamine, serotonin, acetylcholine, histamine, and others, may act at either presynaptic or postsynaptic sites.