A patient presents with anxiety, increased heart rate, and fear. The nurse suspects the activation of which neurotransmitter?

Choice A reason: Histamine regulates wakefulness and allergic responses, not anxiety or fear. Its receptors in the brain promote alertness, but excessive histamine does not drive sympathetic activation like increased heart rate. This makes histamine an incorrect choice for the symptoms described, which align with autonomic arousal. Choice B reason: Acetylcholine mediates parasympathetic responses, like slowing heart rate, not the sympathetic activation seen in anxiety. While it plays a role in attention, it does not primarily cause fear or tachycardia, making it an unsuitable choice compared to norepinephrine’s role in stress responses. Choice C reason: GABA inhibits neural activity, reducing anxiety via GABA-A receptor activation. Low GABA levels may contribute to anxiety, but the symptoms described (tachycardia, fear) result from sympathetic activation, not GABA excess. This makes GABA incorrect for the neurotransmitter driving these symptoms. Choice D reason: Norepinephrine, released during stress, activates the sympathetic nervous system, increasing heart rate and inducing fear via locus coeruleus activation. It heightens arousal in the amygdala, contributing to anxiety symptoms. This aligns with the fight-or-flight response, making norepinephrine the correct neurotransmitter for these symptoms.