Fig 4.

D2 receptor-mediated effects on ERKs phosphorylation and cellular proliferation in the MMQ lactotrop cell line. (A) RT-PCR analysis of the expression of the endogenous D2R isoforms in MMQ cells. (B) Western blots of the time course of ERK activation in MMQ after addition in the medium of 500 nM bromocriptine or 100 nM PMA (TPA). Total level of ERK proteins in each sample is shown as internal control of loaded quantities of protein extracts. (C) Inhibitory effect of bromocriptine and PMA on MMQ cell proliferation measured by [³H]thymidine incorporation. The vehicle value was arbitrarily taken as 100%. **, P < 0.01; ***, P < 0.001 versus vehicle (Student's t test). (D) Effect of different inhibitors and D2R antagonist (U0126 at 10 μM, PD98059 at 50 μM, SB203580 at 5 μM, Ro318220 at 1 μM, haloperidol at 10 μM) on [³H]thymidine incorporation after bromocriptine treatment of MMQ cells. The value of [³H]thymidine incorporation only in the presence of the inhibitors was arbitrarily taken as 100%. **, P < 0.01 versus vehicle (Student's t test).