Lateral hypothalamic syndrome

Douglas Fitts dfitts at u.washington.edu
Sun Jan 19 03:47:33 EST 1997


flefever at ix.netcom.com(F. Frank LeFever) writes:

>Maybe if you're old enough to recognize this term you're too old to be
>surfing the internet, but...

>LHS was a hot item 30-35 years ago (e.g. in J. Comp. Physiol. Psychol.)
>but doubt a Medline search  (especially if limited to Ovid disk) would
>turn up much--wrong time, wrong journals.

>I'd welcome the most recent reference and/or the most through OLD
>reference, OR your personal experience as a brain surgeon on rats!

>I'm especially interested in the exact details of the anorexia and/or
>finickiness of the rats.  It was said that they COULD be coaxed to eat
>with a "palatable" diet (and then through graded steps to
>self-sustained eating with a "normal"  diet).

As I recall, you could get LH lesioned rats to recover just by feeding
them artificially for several weeks -- they'd finally begin eating enough
of the old chow to sustain themselves.  Adding a palatable diet was a way
of speeding up this process.  But see added comments below. 

>What EXACTLY is "palatable"?  Chocolate has been mentioned, and I
>coaxed one rat along with chocolate covered halvah, but do you know of
>systematic studies on the defining characteristics?  (sweetness?
>moistness? other??)

"Palatable" in this case is whatever a recovered lateral hypothalamic
animal will eat :)

Seriously, this is a real problem defining "palatable".  N.J. Kenney at
Univ of Wash has been arguing for several years that the lesion of the
area postrema, which also makes rats aphagic and lose weight, actually
creates a food aversion for the chow the rats were weaned on and ate all
their lives.  These AP lesioned rats, like LH lesioned rats, would readily
eat "palatable" foods but little of their own chow.  Kenney went to some
trouble trying to match palatability and found out that the rats seemed to
prefer something *different*, not just something palatable.  The old chow
now made them "sick".  A new chow of approximately equal palatability
to the old chow would do almost as well as a chocolate chip cookie. 

I have no idea whether this is relevant to the LH rat.  However, it's well
known that abdominal operations of several types (vagotomy, bile duct
ligation, etc.) can cause aversions for flavors consumed before the
operation. The avid intake of a different food then makes it look
"palatable".  Presumably, the flavor becomes associated with the GI
distress accompanying the surgery.  Similar aversions develop during
chemotherapy.

Also, there are specific appetites.  A salt solution of 0.3-0.5 molar is
bad enough tasting to a rat that it will drink very little if it has an
alternative fluid source.  After a depletion of sodium, however, rats
drink this stuff like soda pop. 

Preferences for foods can also be conditioned.  For instance, pairing a
neutral flavor with nutritious consequences can cause a preference for the
flavor.  Something that was neutral is now palatable.

I'm not too sure if any of this is really getting at the question you
asked.  If so, email for more info.

Doug




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