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(b)(3)

I am enclosing copies of the followlng reports which I thtnk will Interest ycu:

1. ComporIson of ALD-52 and LSD-25,

2. Comparison of MLD-41 and LSD-25,

3. Attempted Blocking of LSD-Reactlon by Pretreatment wlth BCL.

As you will note, MiD Is a psychotomlmetic agznt whlch, however, Is considerably less potent than LSD, whereas AlD is at least as potent as LSD. We were again unsuccessful in obtaining any slgnificant degree of blocking of the LSD-reactlon by pretreatment with BOL. I am, therefore, dropping this line of investigation unless you feel that I should study some other dosage schedule.

Aftempted blocking of the LSD-react lon with dibenzyline, the adrenolytic drug, is now ln the preliminary stage. Alt l can say at the moment Is that we have had no untoward effects when O.5. megm./kg. of, LSD was given two hours after I mg./kg. of dibenzyline.

I too am sorry that I wlll not be going to Europe, but my work schedule Is so heavy that I cannot sparz the time.

Very sincerely,

0 Lill Harris Isbell, M. D. Director

Enclosures

4371

Depamof HEALTH, EDUCATION, AND , ELFARE . Public Health Service NATIONAL INSTITUTES OFHEALTH

IN REPLYING ADGRESS THE NATIONAL INSTITOTE OF MENTAL HTALTM ADOICTSON RESTARCH CENTER U.S. PUsLIe HeaLTH SEnviCt HosPTs P. O. Box zaae LE“

25 June 1957