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From: B. Harris)
Subject: Re: Fat  cholesterol and exercise  health
Date: 6 Sep 1998 09:19:50 GMT

In <RcrI1.2128$> "David Lloyd-Jones"
<> writes:

>My question for Greg, however, is When has he heard of fats crossing the
>blood brain barrier?

    FYI, fats cross the blood-brain barrier, and they do it quite
rapidly.  One of the fastest acting surgical anaesthetics, a drug
called Diprivan/propofol (aka "milk of amnesia") looks like milk
because the drug is disolved in plain old Intralipid-- the same
soybean-lecithin fat emulsion they give you intravenously when you're
in need of long term feeding parenterally.  One good bolus of Diprivan
and you're out in 30 seconds-- that's how fast fats cross the blood
brain barrier.

   And it's not simply that the drug crosses the BBB, and the fat
doesn't, for fat-soluble drugs in water alone don't have the same
properties.  For example, disolve melatonin likewise into a stabalized
emulsion of fatty substances suitable for IV use, and you will find
that an IV injection will put an experimental animal into an
incontinent stupor in a few minutes.  Not what you'd expect of
melatonin, but that's because you don't usually see it get into the
brain that fast, and in those quantities.  Melatonin is not terribly
soluble in water, but it goes into saline well enough that you can
verify that injecting comparable amounts of melatonin into the blood
directly doesn't have anything like the pharmaceutical effect that
injecting melatonin disolved on fat micelles does.  Fat soluble drugs
get across the BBB, but remember that fats too are fat-soluble.

   Did you think your brain makes all those complex fats it's made up
of, out of sugar?  Omega-3's (DHA) and all?  Nope.

                                        Steve Harris, M.D.

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