The following statements propose some of the similarities and differences between classic non-peptide neurotransmitters (CNN) and peptide neurotransmitters (PN):
A. CNN are synthesized at the presynaptic terminal while PN are synthesized in the cell body.
B. PN receptors are confined to the specific synapse at which PN is released like that of CNN.
C. When one neuron (containing both CNN and PN) is stimulated at low frequency, both PN and CNN are released from the presynaptic terminal, but at higher frequencies, only CNN is released.
D. The typical action of CNN has short latency and short duration (milliseconds) while PN action may have long latency and may persist for long duration (seconds).
Which one of the following options represents a combination of all correct statements?

Correct option is D

Correct Answer:
Option 4 – A and D
Explanation:
A is correct: CNNs (e.g., glutamate, GABA) are synthesized locally in the presynaptic terminal, whereas peptide neurotransmitters are synthesized in the cell body and transported to terminals.
D is correct: CNNs mediate fast synaptic transmission with short latency and duration, while PNs typically produce slower, longer-lasting effects.
B is incorrect: PN receptors are often extrasynaptic and widely distributed, not confined to a single synapse.
C is incorrect: High-frequency stimulation preferentially releases peptide neurotransmitters, not only CNNs.
Information Booster :
· Neurotransmitter release depends on vesicle type and firing frequency.
· Dense-core vesicles (PN) require higher Ca²⁺ buildup for release.
· Peptide neurotransmitters often act as neuromodulators.
· CNNs mediate rapid point-to-point synaptic signaling.