Prolactin-inhibiting factor

There is some evidence that nickel may have a role in the release of prolactin from the pituitary. In vitro studies have shown that nickel could directly inhibit the release of prolactin by the pituitary, and it has been suggested that nickel may be part of a prolactin inhibiting factor (LaBella et al. 1973). Intravenous exposure to nickel chloride has been shown to reduce semm levels of prolactin in male rats that were pretreated with chlorpromazine, which itself produces hyperprolactinemia (LaBella et al. 

The neurotransmitter Dopamine appears to act as the top dog prolactin-inhibiting factor. Dopamine is secreted into portal blood by the hypothalamic neurons. Next it binds to receptors on lactotrophs, and inhibits both the synthesis and release of prolactin. So chemicals and drugs that interfere with dopamine release or receptor binding also increase the release of prolactin. These... 

Many results have confirmed this conception. A LH- and a FSH-releasing factor have been isolated. A prolactin-inhibiting factor has been convincingly demonstrated. A corticotrophic releasing factor and a TSH releasing-factor have also been isolated. 

Prolactin inhibiting factor (mammals) PIF Prolactin release inhibiting hormone PRIH... 

The release of prolactin from the adenohypophysis is normally inhibited by prolactin-inhibiting hormone (PIH, dopamine) from the hypothalamus. Prolactin secretion is also controlled by prolactin-releasing factor (PRF). The release of PRF from the hypothalamus is mediated by reflexes elicited by suckling and breast stimulation. 

Inhibit prolactin inhibitory factor, thereby increasing prolactin levels Suppress testosterone-mediated stimulation of libido... 

Prolactin (PRL) Protein, MW 20,000 Prolactin release factor (PRF) may or may not be identical to thyrotropin-releasing hormone Prolactin release-inhibiting factor (PIF) most likely dopamine Supports lactation... 

Figure 16.3 Short feedback loop controlling prolactin (PRL) secretion. PRL secretion by the anterior pituitary is normally inhibited by the PRL inhibiting factor (PIF) secreted by hypothalamus. PIF is dopamine. The suckling reflex stops PIF secretion and allows the pituitary to produce and export prolactin. Accumulation of PRL in the pituitary causes its backup through a portal vein into the hypothalamus, eliciting a derepression of PIF production and a subsequent decrease in PRL export.

Thioxanthenes, such as flupenthixol and clopenthixol, are similar in structure to the phenothiazines. The therapeutic effects are similar to those of the piperazine group. Antipsychotic thioxanthenes are thought to benefit psychotic conditions by blocking postsynaptic dopamine receptors in the brain. They also produce an alpha-adrenergic blocking effect and depress the release of most hypothalamic and hypophyseal hormones. However, the concentration of prolactin is increased due to blockade of prolactin inhibitory factor (PIF), which inhibits the release of prolactin from the pituitary gland. 

Some of the effects of antipsychotic drugs on sexual function have been attributed by Aizenberg et al. to increased prolactin secretion by the anterior pituitary (74, 76), other effects may result from their specific autonomic actions (75). Prolactin secretion by the anterior pituitary is tonically inhibited by the hypothalamus, with dopamine acting as the prolactin release-inhibiting factor (PIF). Thus, conventional neuroleptics cause dose-related increases in serum prolactin levels (hy-... 

Prolactin-releasing peptide Prolactin releasing/inhibiting factor... 

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