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Functional characterisation of the human cloned 5‐HT 7 receptor (long form); antagonist profile of SB‐258719
Author(s) -
Thomas David R.,
Gittins Susan A.,
Collin Lissa L.,
Middlemiss Derek N.,
Riley Graham,
Hagan Jim,
Gloger Israel,
Ellis Catherine E.,
Forbes Ian T.,
Brown Anthony M.
Publication year - 1998
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0701946
Subject(s) - adenylyl cyclase , competitive antagonist , ketanserin , agonist , ritanserin , receptor , inverse agonist , partial agonist , receptor antagonist , adcy9 , chemistry , pharmacology , medicine , antagonist , endocrinology , biology , 5 ht receptor , biochemistry , serotonin
1 The functional profile of the long form of the human cloned 5‐HT 7 receptor (designated h5‐HT 7(a) ) was investigated using a number of 5‐HT receptor agonists and antagonists and compared with its binding profile. Receptor function was measured using adenylyl cyclase activity in washed membranes from HEK293 cells stably expressing the recombinant h5‐HT 7(a) receptor. 2 The receptor binding profile, determined by competition with [ 3 H]‐5‐CT, was consistent with that previously reported for the h5‐HT 7(a) receptor. The selective 5‐HT 7 receptor antagonist SB‐258719 ((R)‐3, N ‐Dimethyl‐ N ‐[1‐methyl‐3‐(4‐methylpiperidin‐1‐yl)propyl]benzene sulfonamide) displayed high affinity ( p K i 7.5) for the receptor. 3 In the adenylyl cyclase functional assay, 5‐CT and 8‐OH‐DPAT were both full agonists compared to 5‐HT and the rank order of potency for agonists (5‐CT>5‐HT>8‐OH‐DPAT) was the same in functional and binding studies. 4 Risperidone, methiothepin, mesulergine, clozapine, olanzapine, ketanserin and SB‐258719 antagonised surmountably 5‐CT‐stimulated adenylyl cyclase activity. Schild analysis of the antagonism by SB‐258719 gave a pA 2 of 7.2±0.2 and slope not significantly different from 1, consistent with competitive antagonism. 5 The same antagonists also inhibited basal adenylyl cyclase activity with a rank order of potency in agreement with those for antagonist potency and binding affinity. Both SB‐258719 and mesulergine displayed apparent partial inverse agonist profiles compared to the other antagonists tested. These inhibitory effects of antagonists appear to be 5‐HT 7 receptor‐mediated and to reflect inverse agonism. 6 It is concluded that in this expression system, the h5‐HT 7(a) receptor shows the expected binding and functional profile and displays constitutive activity, revealing inverse agonist activity for a range of antagonists.British Journal of Pharmacology (1998) 124 , 1300–1306; doi: 10.1038/sj.bjp.0701946