Table 1

Effect of arachidonic acid on 5-HT1A receptor binding parameters and receptor-G protein-coupling and activation

VehicleArachidonic Acidn
Saturation binding
 pK d(nM)9.11  ± 0.08 (0.77)9.05  ± 0.0 (0.95)6
B max (fmol/mg of protein)1102  ± 1151276  ± 966
Gpp(NH)p sensitivity
 pIC50 (μM)5.59  ± 0.07 (2.6)5.57  ± 0.08 (2.7)4
E max (% inhibition)95  ± 1%97  ± 1%4
GTP[γ35S] binding
k obs 0.0296  ± 0.0020.0314  ± 0.0045
B max (fmol/mg of protein)164  ± 16154  ± 305

Cells were treated with AA, 10 μM or vehicle (EtOH, 0.1%). The effect of AA treatment on agonist affinity (Kd) and receptor density (Bmax) was measured using [3H]8-OH-DPAT binding in membrane homogenates. AA effects on receptor-G protein-coupling efficiency were studied by measuring the capacity of Gpp(NH)p (a nonhydrolyzable analog of GTP) to reduce high-affinity [3H]8-OH-DPAT binding (1 nM). To assess the capacity of the activated receptor to activate the G protein after AA treatment, the time course (5–60 min) of binding of GTP[γ35S] to G protein was measured in response to activation of 5-HT1A receptors with dp-5-CT (100 nM) and the rate constant (kobs) and maximal binding (Bmax) were calculated. AA did not alter any of the measured parameters (p > 0.05).