The hypophysiotrophic neurones themselves are regulated by hormonal, neuropeptide, and neurotransmitter influences, the latter arising from well-defined bioaminergic pathways that originate in the hypothalamus and elsewhere in the brain (Fig. 1.24). The neurotransmitter dopamine is also a hypophysiotrophic hormone and arises in the hypothalamus from a group of tuberohypophysial neurones. It is secreted into the portal vessel blood and inhibits prolactin secretion. Biogenic amines (including dopamine) influence other pituitary secretions by their effects on hypophysiotrophic neurones.
