Clozapine: Selective Labeling of Sites Resembling 5HT6 Serotonin Receptors May Reflect Psychoactive Profile

Table 3 Comparison of drug affinities for [ ³ H]clozapine binding sites in rat brain and cloned dopamine receptors

Ligand	D₁ nM^a,b	D₂ nM^c	D₃ nM^c	D₄ nM^d	[³H]Clozapine
SCH 23390	0.11	1,000	—	—	—
(+) Butaclamol	0.90	0.83	—	40	1,000
Ketanserin	190	>1,000	—	148	—
Spiperone	220	0.07	0.61	0.05	30
Apomorphine	210	24	20	4.1	50,000
Dopamine	2,500	474	25	28	500,000
Haloperidol	203	0.45	9.8	5.1	400
Bromocriptine	—	5.3	7.4	340	200
Domperidone	—	0.3	9.5	—	6,000
Thioridazine	—	3.3	7.8	12	30
Chlorpromazine	—	2.8	6.1	37	20
Raclopride	—	1.8	3.5	237	>10,000
Eticlopride	—	—	—	2.1	>10,000
Fluphenazine	—	—	—	46	20
Trifluoperazine	—	—	—	3	30
Clozapine	—	56	180	9	10

All numbers represent K_i values from the literature as noted or [³H]clozapine to rat brain membranes. Values for drug potencies at [³H]clozapine binding sites are means of two to three determinations that varied less than 20%.
^aDeary et al. (16)
^bZhou et al. (17)
^cSokoloff et al. (18)
^dVan Tol et al. (9)

ISSN: 1528-3658