Which of the following is most likely the excitatory neurotransmitter released into the synaptic cleft between the inner ear hair cells and their spiral ganglion?
A. GABA
B. Acetylcholine
C. Serotonin
D. Glutamate
Click for Explanation
The neurotransmitter released by the inner ear hair cells is known to directly excite the spiral ganglion it innervates. Glutamate is the most common excitatory neurotransmitter in the brain, making D the most likely answer.
A. GABA: incorrect. GABA is an inhibitory neurotransmitter and would not be likely to directly excite the spiral ganglion.
B. Acetylcholine; incorrect. Acetylcholine does act as an excitatory neurotransmitter at the neuromuscular junction and in the periphery. However, glutamate is the most common excitatory neurotransmitter in the brain, making it the most likely answer.
C. Serotonin; incorrect. Serotonin is an inhibitory neurotransmitter and would not be likely to directly excite the spiral ganglion.
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