THE PSYCHOGENIC EFFECTS OF PROLACTIN

Prolactin modulates maternal functions and is involved in behaviour. B inding sites have been identified in the hypothalamus and substantia n igra. Hyperprolactinaemia stimulates dopamine turnover in several area s of the brain, including the nucleus accumbens, and reduces turnover in other regions, e.g. the substantia nigra. Hyperprolactinaemia stimu lates the opioidergic system. The portal concentration of dopamine and oxytocin (a prolactin stimulatory substance) may be increased in hype rprolactinaemia. In mammals, prolactin is associated with learning, st imulation of the immune response, reduction of body temperature and in creased corticosterone secretion. It is involved in the behavioural as pect of reproduction. Secretion is strongly stimulated in the female r at on exposure to pups. Hyperprolactinaemia in male rats reduces sexua l behaviour. Hyperprolactinaemia reduces libido in both men and women but in men it is also associated with low testosterone levels. There i s evidence that in families characterized by an absent or alcoholic fa ther young girls may be predisposed to develop hyperprolactinaemia lat er in life as a reaction to losses. The underlying mechanism of such a psychosomatic reaction, a typical example of which is pseudopregnancy , may be an extemporaneous activation of a neuroendocrine ''maternal s ubroutine'' characteristic of pregnancy. Prolactinomas may result from somatic changes occurring in activated lactotrophs.