In addition to mentioning research on 5-MeO-T as a guard against radiation, Shulgin also mentions it was investigated as "a potentiator to centrally active drugs" in TiHKAL.
There is also a very interesting statement made in:
"Binding of Indolylalkylamines at 5-HT2 Serotonin Receptors: Examination of a Hydrophobic Binding Region"
Richard A. Glennon et al
J. Med. Chem. 1990,33, pg. 2777-2784
"[3H]Ketanserin labels both the high- and low-affinity states of 5-HT2 receptors whereas [3H]DOB labels only the high-affinity state; thus, for an anticipated agonist, the use of [3H]DOB as radioligand may give more meaningful information. For this reason, the affinities of [3f-3i] were determined for [3H]DOB-labeled 5-HT2 receptors and compared with the affinities of 5-methoxy-[alpha]-methyl-tryptamine and its desmethyl derivative 5-methoxy-tryptamine."
"Typically, 5-HT2A agonists [[ psychedelics ]] bind with about a 50-fold higher affinity at [3H]DOB-labeled receptors relative to their affinity at [3H]ketanserin-labeled receptors; whereas antagonists show little difference in affinity regardless of which radioligand is employed.
Both 5-methoxy-alpha-methyltryptamine (Ki = 7 nM) and 5-methoxytryptamine (Ki = 5 nM) bind at tritiated DOB-labeled receptors with about a 50-fold higher affinity than they display for [3H] ketanserin-labeled 5-HT2 receptors. A similar result is noted for the 5-methoxy-1-propyl derivative (Ki = 12 nM), suggesting that it too is most likely an agonist."
According to those numbers, 5-MeO-T should be an active psychedelic, slightly more potent than 5-MeO-
aMT
. Maybe 5-MeO-T can't cross the blood brain barrier well enough to be active ... maybe it's metabolized too quickly to be active ... or perhaps nobody has tried IV'ing enough of it to check!