Regulation of prolactin secretion: Dopamine is the prolactin‐release inhibiting factor (PIF), but also plays a role as a releasing factor (PRF)

Many in‐depth reviews related to regulations of prolactin secretion are available. We will, therefore, focus on controversial aspects using personal opinion in this review. The neuroendocrine control of prolactin secretion from the anterior pituitary gland involves multiple factors including prolactin‐release inhibiting factor (PIF) and prolactin releasing factor (PRF). The PIF exerts a tonic inhibitory control in the physiological conditions. The PIF should be able to effectively inhibit prolactin release for a lifetime, but the inhibitory action of dopamine cannot be sustained for a long period of time. Perifusion of a high concentration of dopamine (1,000 nM) could not sustain inhibitory action on prolactin release but when a small amount of ascorbic acid (0.1 mM) is added in a low concentration of dopamine (3 nM) solution, prolactin release was inhibited for a long period. Ascorbate is essential for dopamine action to inhibit prolactin release. We have, therefore, concluded that the PIF is dopamine pl...