Bret,

We once used the solution you do, and have changed to the one below because
we now save sections for in situ hybridization.  It substitutes glycerol
for sucrose and is more expensive (especially if you use molecular biology
grade reagents) but well worth it for our purposes.
One feature is that it does not freeze at -30C or even at -40C, but does
freeze at -70C or on dry ice. That makes it useful and convenient for
shipping free floating sections stored in 24 well tissue culture trays.
Even though the solution with tissue freezes, the cryoprotectant prevents
ice crystal artefact and loss of antigenicity or mRNA.  We've not tested
between -40 and -70, so I don't know the exact freezing point.

20% glycerol
30% ethylene glycol
50% 0.1M phosphate buffer
Any good reagent grade chemicals will do, if you are not concerned about
proteases or RNAases.  I keep a bottle of it on hand in the freezer to use
in trays that receive sections as they are cut.  If you don't use it enough
to warrant a stock supply, its quite easy to make quickly in small amounts.

If you need a reference, I described its use in a Journal of
Histotechnology paper:
	Simmons, et al.  A complete protocol for
	in situ hybridization of messenger RNAs
	in brain and other tissues with radiolabeled
	single stranded RNA probes.
	J. Histotech., 12(3):169-181, 1989.

Good luck!  -Donna