TABLE 2

The potency and efficacy of ligands at D2L receptor-G protein fusions

[35S]GTPγS binding studies were performed as described under Materials and Methods on membranes of HEK293 cells transfected to transiently express each of the D2L-G protein fusions. Estimates of pEC50 values (±S.E.M.) for each ligand and agonist efficacy measurements relative to dopamine (±S.E.M.) each are provided.



D2li1

D2li2

D2li3

D2lo1

pEC50
Emax
pEC50
Emax
pEC50
Emax
pEC50
Emax
%DA %DA %DA %DA
Dopamine 5.63 (0.05) 100 5.25 (0.16) 100 4.92 (0.15) 100 6.15 (0.15) 100
m-Tyramine 4.81 (0.14) 50 (2) 4.92 (0.32) 40 (13) 4.97 (0.30) 34 (2) 5.38 (0.03) 74 (3)
p-Tyramine N.A. N.A. N.A. 3.85 (0.20) 53 (4)
R-(+)-3-PPP 4.77 (0.06) 61 (2) 4.67 (0.30) 33 (2) 4.59 (0.23) 41 (10) 5.21 (0.02) 82 (1)
S-(-)-3-PPP N.A. N.A. N.A. 6.25 (0.09) 21 (2)
Quinpirole 5.53 (0.06) 99 (1) 4.72 (0.76) 59 (27) 5.62 (0.42) 55 (15) 6.12 (0.03) 100 (4)
NPA 7.84 (0.45) 143 (6) 7.64 (0.23) 96 (18) 7.48 (0.31) 101 (17) 7.86 (0.58) 109 (5)
7-OH-DPAT
8.12 (0.13)
34 (1)
N.A.

7.83 (0.30)
21 (2)
7.99 (0.21)
51 (1)
  • N.A., no detectable stimulation; %DA, percentage of maximum response to dopamine.