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Whitaker PM, Seeman P. 
“Hallucinogen binding to dopamine/neuroleptic receptors”. 
J.Pharm.Pharmacol.. 1977;29(8):506-07.
The binding of hallucinogens to dopamine/neuroleptic receptors was investigated. Crude homogenates of calf caudate were incubated with 3Hhaloperidol or 3H-apomorphine. The stereoselective component of binding was defined as the amount of either compound bound in the presence of (-)-butaclamol minus that bound in the presence of (+)-butaclamol (Ayers"). Hallucinogens tested were N,N-diethyltryptamine (DET), ibogaine, bufotenin, N,N-dimethyltryptamine (DMT), mianserin (Organon), 2,5-dimethoxy-4-methylamphetamine (STP), mescaline, methysergide (Sandoz), (+)-LSD, 5-methoxy-NN-dimethyltryptamine and 5-HT. Unless otherwise stated all drugs were from Sigma-Chem. DMT, DET, bufotenin and ibogaine were all active on the neuroleptic center (3H-haloperidol) in the nM region. Methysergide and STP were active in the 30-50 nM range while mescaline and LSD blocked in the 100-500 nM range. Tryptamine derivatives which were more potent in blocking the binding haloperidol were much weaker in blocking the binding of apomorphine. LSD had a very low IC50 against apomorphine binding but was less active against haloperidol binding. Tryptamine derivatives may reciprocally affect both the antagonist as well as the agonist state of the dopamine receptor. Conformational similarities with dopamine are discussed. Conclusion There may be a tryptaminergic as well as dopaminergic component of haloperidol binding.
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