Irreversible blockade of central 5-HT1A receptor binding sites by the photoaffinity probe 8-methoxy-3'-NAP-amino-PAT.
A new photoaffinity ligand derived from the potent 5-HT agonist, 8-OH-DPAT, has been synthesized. In the dark, this compound, 8-methoxy-2-(N-n-propyl,N-3-(2-nitro-4-azidophenyl)aminopropyl) aminotetralin or 8-methoxy-3'-NAP-amino-PAT, displaced [3H]8-OH-DPAT and [3H]5-HT bound to 5-HT1A and 5-HT1 sites in hippocampal membranes with IC50 values of 6.6 and 18.1 nM respectively. The apparent affinity of 8-methoxy-3'-NAP-amino-PAT for the 5-HT1A binding sites was at least 20 times higher than for the other 5-HT receptor sites (5-HT2 and 5-HT3) or the dopamine-related [3H]spiperone and [3H]7-OH-DPAT binding sites. Under UV irradiation (lambda = 366 nm), 8-methoxy-3'-NAP-amino-PAT produced an irreversible blockade of 5-HT1A sites which could be prevented by prior site occupancy by a saturating concentration (10 microM) of reversible 5-HT ligands such as 5-HT itself, 8-OH-DPAT or LSD. The blockade of 5-HT1A binding sites was concentration-dependent, and two successive irradiations of rat brain membranes in the presence of 30 nM 8-methoxy-3'-NAP-amino-PAT were found to be more efficient that a single exposure to 100 nM of the photosensitive ligand. Thus, a 55-60% irreversible blockade of 5-HT1A binding sites was achieved following 2 cumulative irradiations of hippocampal membranes with 30 nM 8-methoxy-3'-NAP-amino-PAT. Under such conditions, cortical 5-HT2 receptor binding sites as well as striatal 5-HT3 and dopamine-related binding sites remained unaltered.
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000345:Affinity Labels / Q000138:chemical synthesis / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008027:Light; D008297:Male; D009281:Naphthalenes / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000378:metabolism* / Q000528:radiation effects; D012701:Serotonin / Q000378:metabolism; D013764:Tetrahydronaphthalenes / Q000138:chemical synthesis / Q000378:metabolism*
D000345:Affinity Labels; D009281:Naphthalenes; D011985:Receptors, Serotonin; D013764:Tetrahydronaphthalenes; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin