Abstract :
Salsolinol (a derivative of dopamine) is involved in the stimulatory mechanism of pituitary
prolactin (PRL) release in lactating sheep. In the current study, we examined a hypothesis
that salsolinol could also affect the expression of the PRL gene in the ovine anterior pituitary
(AP). Two experiments, in vivo and in vitro, were performed 48 h after lambs weaning in
order to verify this hypothesis on sheep. In the in vivo experiment, sheep were infused
intracerebroventriculary with salsolinol (total 150 g) or a vehicle (control) in a series of
five 30-min infusions at 30-min intervals. In the in vitro experiment, the explants of the
AP tissue from another group of lactating sheep were incubated in a medium containing
of 20 or 100 g/ml of salsolinol for two 30-min periods with 15-min interval or in a pure
medium (control). In the course of these experiments, blood or medium samples were
collected every 10 or 15 min., respectively, to measure the prolactin concentration. The
PRL mRNA expression was determined in the AP by real-time PCR. Salsolinol significantly
increased the amount of PRL mRNA in the AP, compared to the control (P < 0.01 for in vivo;
P < 0.01 and P < 0.001 for lower and higher in vitro dose, respectively). The concentrations
of PRL in plasma and medium were also significantly higher in salsolinol-treated groups,
compared to controls (P < 0.001 and P < 0.05 for in vivo and higher in vitro dose, respectively).
In conclusion, salsolinol plays a pivotal role in the regulation of both the pituitary PRL
synthesis and release in lactating sheep.
