Table 1.

Effects of antagonists on inward currents and cAMP responses initiated in Xenopus oocytes expressing theDrosophila DopR99B receptor

Antagonists (10 μm)Percentage of inward current* responses to 1 μm dopamine (n)Percentage of cAMP responses to 10 μm dopamine (n)Receptor type specificity
Flupentixol3.9  ± 1.6 (5)8.4  ± 3.7  (10)D1/D2-like
R(+) SCH2339034.2  ± 8.9 (6)31.4  ± 9.7  (10)D1/D5
S(−)-Sulpiride56.8  ± 16.1 (5)75.5  ± 6.2  (10)D2-like
Spiperone63.0  ± 9.2 (7)82.3  ± 9.6  (10)D2-like
(+)-Butaclamol66.7  ± 4.5 (6)73.8  ± 7.9  (8)D2/D1-like
Phentolamine71.6  ± 7.1 (6)64.6  ± 14.9  (10)α-Adrenergic
dl-Propranolol89.6  ± 5.9 (7)108.5  ± 22.9  (10)β-Adrenergic
S-(−)-Eticlopride103.2  ± 10.9 (4)103.0  ± 17.6  (10)D2-like
Domperidone118.3  ± 7.0 (3)117.0  ± 18.6  (10)Peripheral D2
  • The size of the inward current response to a 2 min pulse of 1 μm dopamine given in the presence of 10 μmantagonist is expressed as a percentage ± SE of the response to a control dopamine pulse given to the same oocyte. The mean response to a 2 min control pulse of 1 μm dopamine was 331.4 ± 15.6 nA (n = 73). Antagonists alone did not initiate any currents. The size of the cAMP response to a 30 min exposure to 10 μm dopamine in the presence of 10 μmantagonist and 100 μm IBMX after a 30 min preincubation in the presence of 100 μm IBMX alone is expressed as a percentage ± SE of the response to a control dopamine exposure. The mean response to a 30 min exposure to 10 μm dopamine was an increase of 2.57 ± 0.42 pmol cAMP/oocyte. Antagonists alone did not initiate any cAMP responses.

  • * Data reproduced from Feng et al. (1996) for comparison.