Table 2.

EC50 values (μm) and Hill coefficients for 5-HT activation of 143-Tyr mutant receptors (A) and [3H]granisetron binding affinities of Tyr mutants (B)

A
143- EC50 ± SE nH ± SE
Ala 354 ± 29.0* 2.62 ± 0.53
Ser 472 ± 47.9* 2.68 ± 0.62
Phe 78.6 ± 2.86* 2.73 ± 0.21
4-F-Phe NR NR
Tyr (WT) 1.15 ± 0.03 2.98 ± 0.19
mTyr NR NR
4-MeO-Phe NR NR
hTyr 33.24 ± 2.60* 1.80 ± 0.22*
l-DOPA 7.16 ± 0.90* 2.34 ± 0.54
B
143- Kd (nm) n
Ala 1.2 ± 0.24 8
Ser 1.13 ± 0.23 7
Phe 0.53 ± 0.10 3
Tyr (WT) 0.32 ± 0.035 7
  • Asterisks indicate a significant difference (p<0.05) to Tyr (n = 3-6). Data in B are from Price and Lummis (2004). Substitutions have been approximately ordered by increasing size. NR, No response to concentrations of 5-HT up to 1 mm; NB, no binding; WT, wild type.