Functional and radioligand binding characterization of rat 5-HT6 receptors stably expressed in HEK293 cells.

We have stably expressed the rat 5-HT6 receptor in HEK293 cells at a density of > 2 pmol/mg protein, as determined in equilibrium binding studies with [3H]-LSD and [3H]-5-HT and compared the affinity of a range of compounds in competition binding experiments with either [3H]-LSD or [3H]-5-HT as radioligand. A variety of tryptamine derivatives were tested and showed a significantly higher affinity when the 5-HT6 receptor was labelled with [3H]-5-HT, whereas ergoline compounds and several antagonists had higher affinities when [3H]-LSD was used as radioligand. Subsequently we examined the ability of LSD, 5-HT and a number of tryptamine derivatives to stimulate cAMP accumulation in order to determine their agonist potency and efficacy.

Identification of 5-hydroxytryptamine7 receptor binding sites in rat hypothalamus: sensitivity to chronic antidepressant treatment.

Due to the high level of expression of mRNA for the 5-hydroxytrytamine (5-ht7) receptor in the hypothalamus and the high affinity of 5-HT for this receptor, [3H]5-HT binding was performed in rat hypothalamus to determine whether 5-ht7 receptor binding sites are present in animal tissue. [3H]5-HT binding was performed in the presence of 100 nM pindolol, which is inactive at 5-ht7 receptors but prevents the binding of [3H]5-HT to 5-HT1A and 5-HT1B receptor binding sites. Under these conditions, [3H]5-HT bound to a binding site with an affinity of 1.