Antipsychotics potentiate LSD?

[Vader]

I have an abstract here (Murphree et al, 1961, "Threshold Doses of Lysergic Acid Diethylamide, a Method for Exploring Antagonism of this Drug by Other Agents"), that says that subjects trained to recognise LSD, who were ordinarily able to detect a dose of 20 ug, could detect 15ug when administered with 25mg of chlorpromazine.
What? This just makes no sense to me. How could a 5-HT2A antagonist increase the effects of LSD? Does anyone have any experience or theoretical knowledge that can shed some light?

 

[f1ct]

Link / DOI?

EDIT: "Digital Object Identifier..." heh.

 

[invert]

How could a 5-HT2A antagonist increase the effects of LSD?

Well, I suppose if the serotonergic activity it was suppressing had inhibitory effects on brain areas with a role in the perceptibility of near-threshold doses of LSD, that might do it. As to what those brain areas might be, I've no idea. Not my area, this, but something to do with inhibiting inhibition seems a plausible way for this to work.

By the way, from the point of view of the present, chlorpromazine isn't called atypical, indeed it's one of the oldest and most typical (of the ones that followed) antipsychotics.

 

[Vader]

I have a paper abstract, sorry. Federation Proceedings, 1961, 20(1) (part 1), 397.
The text of the abstract is:

Using a double blind technic, normal human subjects, trained to recognize the behavioral effects of lysergic acid diethylamide (LSD) and other drugs were tested for thresholds using a randomized schedule of LSD or placebo in small doses. Threshold for perception of LSD was 20ug/70kg. Chlorpromazine in a dose of 25mg given simultaneously did not raise this threshold (P less than 0.02) but increased the subjects' sensitivity to LSD, enabling them to recognize 15ug

By the way, from the point of view of the present, chlorpromazine isn't called atypical, indeed it's one of the oldest and most typical (of the ones that followed) antipsychotics.

Yeah my bad entirely, sorry. If a mod could retitle please, that'd be swell.