An electrophilic affinity ligand based on (+)-MK801 distinguishes PCP site 1 from PCP site 2.
The electrophilic affinity ligand, (+)-3-isothiocyanato-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cycl ohepten-5,10 - imine hydrochloride [(+)-MK801-NCS] was characterized for its ability to acrylate phencyclidine (PCP) and sigma binding sites in vivo. Initial studies, conducted with mouse brain membranes, characterized the binding sites labeled by [3H]1-[1-(2-thienyl)cyclohexyl]piperidine ([3H]TCP). The Kd values of [3H]TCP for PCP site 1 (MK801-sensitive) and PCP site 2 (MK801-insensitive) were 12 nM and 68 nM, with Bmax values of 1442 and 734 fmol/mg protein, respectively. Mice were sacrificed 18-24 hours following intracerebroventricular administration of the acylator. The administration of (+)-MK801-NCS increased [3H]TCP binding to site 2, but not to site 1. Although (+)-MK801-NCS decreased [3H](+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d; ccyclohepten-5,10-imine maleate ([3H](+)-MK801) binding to site 1, it had no effect on [3H]TCP binding to site 1. Viewed collectively with other published data, these data support the hypothesis that PCP sites 1 and 2 are distinct binding sites, and that [3H]TCP and [3H](+)-MK801 label different domains of the PCP binding site associated with the NMDA receptor.
Akunne
H C
HC
Clinical Psychopharmacology Section, NIDA/NIH Addiction Research Center, Baltimore, MD 21224.
Monn
J A
JA
Thurkauf
A
A
Jacobson
A E
AE
Rice
K C
KC
Linders
J T
JT
Jiang
Q
Q
Porreca
F
F
Rothman
R B
RB
D000345:Affinity Labels; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology*; D016291:Dizocilpine Maleate / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology*; D013287:Illicit Drugs / Q000378:metabolism; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D010622:Phencyclidine / Q000031:analogs & derivatives* / Q000378:metabolism*; D017478:Receptors, Phencyclidine / Q000187:drug effects / Q000378:metabolism*
D000345:Affinity Labels; D013287:Illicit Drugs; D017478:Receptors, Phencyclidine; C082821:3-isothiocyanato-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine; D016291:Dizocilpine Maleate; C012058:tenocyclidine; D010622:Phencyclidine