Thioridazine stimulates prolactin secretion in man.

Area of Science:

• Neuropharmacology
• Endocrinology
• Psychiatry

Background:

• Thioridazine exhibits weak dopamine antagonism in many brain regions, contrasting with other antipsychotics.
• The tuberoinfundibular tract regulates prolactin secretion via hypothalamic prolactin-inhibiting factor.
• Other phenothiazines, like chlorpromazine, stimulate prolactin secretion.

Purpose of the Study:

• To indirectly assess thioridazine's dopamine antagonism in the tuberoinfundibular tract.
• To investigate thioridazine's effect on prolactin secretion.
• To evaluate the tuberoinfundibular system as a model for studying antipsychotic drug effects.

Main Methods:

• Five healthy male participants were administered 50 mg of chlorpromazine concentrate and 50 mg of thioridazine concentrate in separate trials.
• Prolactin secretion levels were monitored within two hours post-administration for both drugs.

Main Results:

• Both chlorpromazine and thioridazine significantly stimulated prolactin secretion within two hours.
• Thioridazine demonstrated a notable effect on prolactin secretion, indicating dopamine antagonism.

Conclusions:

• Thioridazine is a potent dopamine antagonist within the tuberoinfundibular dopaminergic system.
• The regulation of prolactin secretion serves as a viable indicator for studying antipsychotic drug efficacy in humans.