Differential pharmacology between the guinea‐pig and the gorilla 5‐HT_1D receptor as probed with isochromans (5‐HT_1D‐selective ligands)

Abstract

1 Both the 5-HT 1D and 5-HT 1B receptors are implicated in migraine pathophysiology. Recently isochromans have been discovered to bind primate 5-HT 1D receptors with much higher a nity than 5-HT 1B receptors. In the guinea-pig, a primary animal model for anti-migraine drug testing, however, isochromans bound the 5-HT 1D receptor with lower a nity than the gorilla receptor. 2 This species-speci®c pharmacology was investigated, using site-directed mutagenesis on cloned guinea-pig receptors heterologously expressed in human embryonic kidney 293 cells. Mutations of threonine 100 and arginine 102 at the extracellular side of transmembrane II of the guinea-pig 5-HT 1D receptor to the corresponding primate residues, isoleucine and histidine, respectively, enhanced its a nity for isochromans to that of the gorilla receptor, with little e ects on its a nities for serotonin, sumatriptan and metergoline. Free energy change from the R102H mutation was about twice as much as that from the T100I mutation. 3 For G protein-coupling, serotonin marginally enhanced GTPg 35 S binding in membranes expressing the guinea-pig 5-HT 1D receptor and its mutants, but robustly in membranes expressing the gorilla receptor. Sumatriptan enhanced GTPg 35 S binding in the latter nearly as much as serotonin, and several isochromans by 30 ± 60% of serotonin. 4 We discovered key di erences in the function and binding properties of guinea-pig and gorilla 5-HT 1D receptors, and identi®ed contributions of I100 and H102 of primate 5-HT 1D receptors to isochroman binding. Among common experimental animals, only the rabbit shares I100 and H102 with primates, and could be useful for studying isochroman actions in vivo.

Neurogenic inflammation in the context of migraine

“…It is, however, notable that PNU-142633F was discovered by screening efforts utilizing gorilla cloned 5-HT 1D receptors, which have similar pharmacology to human receptors (Pregenzer et al, 1997). In this model system, PNU-142633F had only 33% of the efficacy of 5-HT as measured using GTP␥ 35 S binding whereas sumatriptan had an efficacy of 93% (Pregenzer et al, 1999). Since 5-HT 1D receptors are found on trigeminal nerve terminals and their ability to shut down firing is both drug-efficacy and firingfrequency dependent, the failure of PNU-142,633F may simply be because it does not have sufficient efficacy at 5-HT 1D receptors.…”

Molecular cloning, sequence analysis and pharmacological properties of the porcine 5‐HT1D receptor

“…Indeed, this is also the case with ketanserin, which has a moderate selectivity for the 5-HT 1D over the 5-HT 1B receptors in the human (Zgombick et al, 1995;, rabbit (Harwood et al, 1995;Bard et al, 1996), rat (Bach et al, 1993;Wurch et al, 1997) and guinea-pig , but not in the dog (Zgombick et al, 1991). Similarly, certain isochroman derivatives show a di erential pharmacology at the guineapig and gorilla 5-HT 1D receptors (Pregenzer et al, 1999). Such species di erences in the pharmacology of homologue receptors can be used to explore the role of divergent amino acid residues in the receptor-ligand interaction as well as the validation of animal models with respect to drug discovery for human diseases.…”

Clozapine and glycinamide prevent MK-801-induced deficits in the novel object recognition (NOR) test in the domestic rabbit (Oryctolagus cuniculus)

“…First, it involves a non-rodent species, the European rabbit (O. cuniculus), that has to our knowledge never before been studied in the context of modeling schizophrenia. Although in recent years the rabbit has become a somewhat unconventional laboratory species, in the present context it offers several potential advantages: its presynaptic serotonin autoreceptors are of the 5-HT1D subtype and highly homologous to those of the human, which are also 5-HT1D (unlike those of the rodent, which are of the 5-HT1B subtype [16,38,52]); the pharmacology of rabbit 5-HT2A and 5-HT2C receptors is also similar to the human (as determined by binding studies using the antagonists MDL100,907 and mesulergine [2]). Rabbits are more comparable to humans with respect to the staging of their brain development during the perinatal period, which has made them attractive for modeling human Fig.…”