Final answer:
PIH stands for prolactin-inhibiting hormone, which is the neurotransmitter dopamine, playing a significant role in the brain's dopaminergic system and in regulating prolactin secretion.
Step-by-step explanation:
The acronym PIH stands for prolactin-inhibiting hormone, which is actually the neurotransmitter dopamine. In non-pregnant females, prolactin secretion is inhibited by prolactin-inhibiting hormone (PIH), and it is only during pregnancy that prolactin levels rise in response to prolactin-releasing hormone (PRH) from the hypothalamus. Dopamine itself plays a significant role in the dopaminergic system, which has an array of dopamine receptors across the brain. It is crucial for the modulation of mood, cognition, and motor control. Dopamine is also involved in a variety of physiological processes and is removed from the synaptic cleft by transport proteins.
Referring to the options listed in the question, (D) NE, or norepinephrine, is often called noradrenaline and is part of the adrenergic neurotransmitter system.