[Changes in plasma prolactin and magnesium in male rats treated with thioproperazine and/or bromocriptine]

The Ca2+ dependent release of both dopamine (DA) and prolactin (Prl) is modified by stress. Plasma magnesium (Mg) concentrations are also modified. Therefore, we have investigated on plasma (P) Mg and Prl, the immediate and delayed effects of one, five or six daily injections of bromocriptine (BMC, 200 micrograms/100 g) and thioproperazine (100 micrograms/100 g), respectively agonist and antagonist of pituitary DA receptors. One hour after injection of either drugs, an increased P Mg is observed while P Prl is increased or decreased. No correlation is, thus, established between P Prl and P Mg changes. The P Mg increase is long-lasting after BMC, transitory after thioproperazine as shown by determinations performed 23 h after the 5th injection. When the two drugs are simultaneously given, no important modifications of P Mg are observed. The mechanisms and consequences of this P Mg increase are discussed. During stress, the hypermagnesemia could modulate the Prl secretion and action, hindering its secretion on one hand, and potentiating its action on target-organs, on the other hand.