What is a common inhibitory neurotransmitter?

Choice A reason: Hyperglycemia causes polyuria as high blood glucose exceeds renal reabsorption capacity, leading to osmotic diuresis. Excess glucose in urine draws water, increasing urine output, a classic diabetes symptom, making this a correct manifestation.

Choice B reason: Polyphagia, or increased hunger, occurs in hyperglycemia as cells cannot utilize glucose due to insulin deficiency or resistance, signaling energy deficit. The body craves food to compensate, making this a correct manifestation.

Choice C reason: Excessive thirst (polydipsia) results from hyperglycemia-induced polyuria, causing dehydration. The body signals thirst to replenish fluid loss from osmotic diuresis, a hallmark of diabetes, making this a correct manifestation.

Choice D reason: Photophobia, sensitivity to light, is not associated with hyperglycemia. It occurs in conditions like meningitis or migraines, not metabolic disturbances like diabetes, making this choice incorrect for hyperglycemia manifestations.

Choice E reason: Dysphagia, difficulty swallowing, is unrelated to hyperglycemia. It may occur in neurological or esophageal disorders, not as a direct result of high blood glucose, making this choice incorrect for hyperglycemia.

Choice A reason: Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system, reducing neuronal excitability by opening chloride channels, hyperpolarizing neurons, and preventing action potentials, making this the correct choice.

Choice B reason: Norepinephrine is an excitatory neurotransmitter and hormone, increasing neuronal activity and arousal in the sympathetic nervous system. It does not inhibit neural signaling, making this choice incorrect for an inhibitory neurotransmitter.

Choice C reason: Histamine acts as a neurotransmitter promoting wakefulness and arousal, not inhibition. It stimulates neuronal activity in the brain, unlike inhibitory neurotransmitters that reduce firing, making this choice incorrect for the role.

Choice D reason: Glutamate is the primary excitatory neurotransmitter, promoting neuronal firing by depolarizing neurons via ion channel activation. It does not inhibit neural activity, making this choice incorrect for an inhibitory neurotransmitter.