Pulp,
Yes, take a look through TiHKAL. Look at #6 (DMT) and #46 (5-MES-DMT) (among other things.)
The DMT entry is a fine list of the most practical procedures for dequaternization. The possibilities seem to fall into three categories: demethylation by brute force via pyrolysis, reduction with a strongly nucleophilic reducing agent, and treating the quat salt with a strong nucleophile (and a little heat.)
Pyrolysis is used by Shulgin in TiHKAL#6, but also (among other places): Org RxN's 7, 142; 1953 (Review), and
Org RxN's 11, 317; 1960 (another review).
For reducing reagents, the extremely nucleophilic reagent LiEt3BH ("Superhydride(R)") has been demonstrated by Shulgin in his DMT entry, and it makes perfect sense that it would be the reducing agent of choice for this situation. Also, LiAlH4 has been used, such as in the case of Bull. Korean Chem. Soc., 20(4), 466-468; 1999, and J. Am. Chem. Soc. 82, 4651; 1960, and J. Chem. Soc. 1729; 1965. Lithium metal is used in C. R. Acad. Sci., Ser. II: Mec., Phys., Chim., Astron., 320(10), 539-43; 1995.
As for examples of strong base, there's the refrences from TiHKAL listed, as well as J.Labelled Compd.Radiopharm. 41(12), 1127 - 1144; 1998 -- where 1,4-diazabicyclo[2.2.2]octane (a.k.a. Dabco(tm), TED, triethylenediamine) is used with great success, and again in J. Org. Chem., 50(25), 5440-1; 1985. Triethylamine is also used in Collect. Czech. Chem. Commun., 50(6), 1415-21; 1985. Sodium thiophenol is used in J. Chem. Soc. 1729; 1965, and Tet. Lett. 1375; 1966, and Hoppe-Seyler's Z.Physiol.Chem. 352, 1058-1064; 1971. The classic example of ethanolamine being used in this manner is Ber. 90, 395, 403; 1957.
Yet another approach is to treat the quaternary amine as a leaving group, and replace it with another dialkyated amine. This is nice since you can use your quaternary salt to make whatever disulstituted tryptamine you want! Here are a few references on that topic:
J. Fluorine Chem., 90(1), 29-38; 1998
Chem. Lett., (9), 893-894; 1997
J. Org. Chem., 61(10), 3228-9; 1996
Tetrahedron Lett., 36(40), 7267-70; 1995
Synlett, (5), 353-4; 1993
I hope you enjoy.
"Freebase emulsions: spot on!"