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Kräuchi K, Feer H, Lichtsteiner M, Wirz-Justice A. 
“Specific in vivo Binding of d-LSD in Rat Brain”. 
Experientia. 1978;34(6):761-62.
A reproducible in vivo d-LSD binding method in rat brain is described. Methods Adult male Wistar 180-220 g rats were i v. injected with 3H d-LSD (1.5 mcg/kg in 200 mcl 0.1% ascorbic acid), 30 min prior to sacrifice. Brains were removed and the cerebellum (CE), cortex, striatum (ST), medulla and pons, thalamus and hypothala mus, and hippocampus dissected out. Eachregion was homogeni" red and aliquots shaken with Soluene and Instagel. Samples were counted for 10 min in a scintillation counter. Increasing doses of cold d- or 1-LSD (both Sandoz) were simultaneously i.v. injected with 3H-d -LSD in displacement experiments.In further experiments, the following were i.p. injected in 500mcl saline at different times before i.v. injection of 3H-d-LSD: apomorphine (5 mg/kg, 60 mix before d-LSD); 1-5HTP-ethylester (Roche; 100 mg/kg, 120 min before); haloperidol (1.25 mg/kg 90 min before) and methiothepin (Roche, 20 mg/kg, 120 min before). Results Total 3H-d:-LS D binding showed reproducible regional differences, being highest in ST and lowest in CE. Dose dependent displacement by unlabeled d-LSD was found in vivo, this being most prominent in the ST. Maximally, 20 pmole/g wet weight could be bound in the ST with a dissociation constant Kd of 5 pmole/g. In the CE, a negligible amount of saturable d-LSD binding was found. Stereospecificity of d-LSD was shown by the fact that specific binding could be reduced by the d- but not the 1-enantiomer of unlabeled LSD injected simultaneously even at a high dose of 150 mcg/kg. In the ST, neither apomorphine nor 1-5HTP-ethylester had a noticeable effect whereas haloperidol and methiothepin markedly reduced 3H-d-LSD binding. Conclusion d LSD binding to dopaminergic and serotoninergic receptors in vivo is characterized by high affinity, stereospecificity and regional selectivity.
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