RT Journal Article
SR Electronic
T1 (R)-(-)-[77Br]4-bromo-2,5-dimethoxyamphetamine labels a novel 5-hydroxytryptamine binding site in brain membranes.
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 537
OP 542
VO 34
IS 4
A1 Peroutka, S J
A1 Hamik, A
A1 Harrington, M A
A1 Hoffman, A J
A1 Mathis, C A
A1 Pierce, P A
A1 Wang, S S
YR 1988
UL http://molpharm.aspetjournals.org/content/34/4/537.abstract
AB (R)-(-)-[77Br]4-Bromo-2,5-dimethoxyamphetamine [(R)-(-)-[77Br] DOB] was synthesized to a high specific activity (1875 +/- 50 Ci/mmol) and used to label membrane-associated recognition sites in rat brain. (R)-(-)-[77Br]DOB displayed high affinity (KD = 0.60 +/- 0.08 nM) for a relatively low density of binding sites (Bmax = 1.2 +/- 0.08 pmol/g of tissue) in rat cortical membranes as compared with [3H]ketanserin (KD = 0.65 +/- 0.1 nM; Bmax = 6.2 +/- 0.6 pmol/g of tissue). Guanine, but not adenine, nucleotides were found to inhibit specific (R)-(-)-[77Br]DOB binding. GTP (10(-4) M) did not eliminate specific (R)-(-)-[77Br]DOB binding but caused a competitive inhibition of the radioligand. Drug competition studies of 5-hydroxytryptamine (5-HT) and related agents indicate that both putative agonists and antagonists display nanomolar potency for these sites. A significant correlation (p less than 0.01) exists between drug potencies for (R)-(-)-[77Br]DOB-labeled sites and both 5-HT2 (r = 0.64) and 5-HT1C (r = 0.68) binding sites. However, the sites do not appear to be identical. Moreover, a significant correlation exists between drug potencies for (R)-(-)-[77Br]DOB-labeled sites and human hallucinogenic drug potencies (r = 0.89; p less than 0.01). We conclude that (R)-(-)-[77Br]DOB labels a unique 5-HT recognition site in rat brain that does not coincide with previously described 5-HT binding site subtypes. The (R)-(-)-[77Br]DOB site does not appear to be a high affinity "state" of the 5-HT2 receptor but may label a subset of heterogeneous 5-HT2 recognition sites.