Fig. 8. The effect of the D1-selective agonists SKF81297 and dihydrexidine on the albumen gland glycoprotein secretion. (A) The partial D1 agonist SKF81297 (50 µmol l^-1) induced a modest but statistically significant increase in glycoprotein secretion compared with control (CON) glands in saline. However, it was less than half the potency of dopamine (DA) at 50 µmol l^-1 concentration. Bars represent the mean ± S.E.M. of 16–18 samples (^*P<0.05; ^*P<0.001, Tukey test). (B) Dihydrexidine (DH) caused a dose-dependent increase in albumen gland glycoprotein secretion between 1 and 100 µmol l^-1. Note that the shape and magnitude of the dose–response curve for dihydrexidine are similar to those of dopamine. Each point represents the mean ± S.E.M. of 18 samples (^*P<0.05; ^*P<0.001, Tukey test).