A bioactive peptide from the transmembrane 5-intracellular loop 3 region of the human 5HT1a receptor.

15 amino acid peptide from the transmembrane 5-intracellular loop 3 region of the human 5HT1a receptor produced concentration-dependent decreases in agonist binding. This result is consistent with a competitive interaction between peptide, receptor, and G protein at the receptor-G protein interface. Bombesin and a 13 amino acid peptide from the carboxyl terminus region of the receptor were inactive.

Activity of Parthenolide at 5HT2A receptors.

Parthenolide displaces [3H]ketanserin from 5HT2A receptors from rat and rabbit brain and cloned 5HT2A receptors. Ki's are in the 100-250 microM range. These results suggest that parthenolide may be a low-affinity antagonist at 5HT receptors; it is unlikely that the entire mechanism of action can be explained by its modest 5HT2A receptor affinity.

Rabbit cerebral cortex 5HT1a receptors.

Selective 5HT1a agonist binding to membranes from rabbit cerebral cortex was concentration-dependent and saturable; the Kd was 1.1 nM and Bmax of 480 fmols/mg protein. Scatchard as well as Hill plots were linear; the Hill coefficient was 0.