Figure 2.

Expression of dopamine D₂ receptors on OSR1⁺ cells and effects of D₂ receptor agonists and an antagonist. (a) RT-PCR analysis of dopamine D₂ receptor mRNA expression in OSR1⁺ cells. (b) Immunofluorescence staining of dopamine D₂ receptors on OSR1⁺ cells. Rat adrenal chromaffin cell line PC-12 was also stained as a positive control because it is known to express dopamine D₁ and D₂ receptors^38,39. Scale bar, 50 μm. (c) Levels of 3β-HSD2 mRNA expression in OSR1⁺ cells treated with dopamine D₂ receptor agonists, including 10 μM quinpirole, 1 μM bromocriptine and 10 μM propylnorapomorphine. Expression levels are normalised to that of a housekeeping gene, β-actin. Student’s t-test was used for comparison of two groups. *P < 0.05. Data represent mean SEM of four independent experiments (n = 4). (d) Levels of 3β-HSD2 mRNA expression in OSR1⁺ cells treated with cabergoline and a dopamine D₂ receptor antagonist. Cells were treated with 20 µM cabergoline under daily administration of 10 μM metoclopramide. Statistical analysis was performed using two-tailed unpaired Student’s t-test with Holm–Bonferroni correction. **P < 0.01. Data represent mean ± SEM of four independent experiments (n = 4).