Which of the following neurotransmitters typically has inhibitory effects?

• A. Glutamate
• B. Norepinephrine
• C. Substance P
• D. None of the listed responses is correct.
• E. Gamma-aminobutyric acid (GABA)

Answer: (E)

Verified step by step guidance

1. Begin by understanding the role of neurotransmitters in the nervous system. Neurotransmitters are chemical messengers that transmit signals across synapses from one neuron to another, influencing various physiological functions.
2. Recognize that neurotransmitters can have either excitatory or inhibitory effects on the postsynaptic neuron. Excitatory neurotransmitters promote the generation of an action potential, while inhibitory neurotransmitters prevent it.
3. Identify the neurotransmitters listed in the problem: Glutamate, Norepinephrine, and Substance P. Research their typical effects on neurons. Glutamate is known for its excitatory effects, Norepinephrine can be excitatory or modulatory, and Substance P is involved in pain perception.
4. Understand that Gamma-aminobutyric acid (GABA) is a well-known inhibitory neurotransmitter. It works by opening ion channels that allow negatively charged ions to enter the neuron, making it less likely to fire an action potential.
5. Conclude that none of the listed neurotransmitters in the problem typically have inhibitory effects, and the correct answer is GABA, which is not among the options provided.