Effects of Manganese Exposure on Dopamine and Prolactin Production in Rat

Although manganese (Mn) has been shown to increase prolactin (PRL) by decreasing dopamine (DA) in the hypothalamus, the mechanism of Mn-induced regulation of the hypothalamic-hypophyseal-pituitary axis is unclear. We assessed the effects of inhaled Mn on hypothalamic DA and pituitary PRL production and evaluated the role of pituitary-specific transacting factor 1 (Pit-1), a transacting factor of PRL gene, in Mn-induced changes in PRL secretion in the rat brain. Male rats exposed to Mn for 4 or 13 weeks (1.5 mg/m 3 , 6 h/day, 5 days/week) showed a progressive and significant decrease in hypothalamic DA, whereas PRL and Pit-1 mRNA levels increased in response to Mn exposure. These results suggest that exposure to Mn decreases hypothalamic DA and promotes the production of PRL in the pituitary and that Pit-1 might be a regulator of DA and PRL.