[CH] Dinosaurs, Toads, and Chiles

peter g (peter.g@telus.net)
Fri, 01 Mar 2002 21:04:20 -0800 

Hey HotHeads ...
    here's an abbreviated version of an online item from BioMedNet.
more in-depth info, including ... receptor fragments, transmembrane
domains, and cytoplasmic loops ... may be found by registering at
www.bmn.com , then checking the magazine section for the full article.
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 "           *** Some like it hot ***
by Karin Römisch
How come birds (and toads!) can eat the most fiery jalapenos?
It turns out that the pain-producing substance in hot peppers, the
 vanilloid capsaicin, can only be sensed by mammals.
The vanilloid receptor is a non-selective cation channel, formed by the
polytopic membrane protein VR1, which can also be activated by
heat; thus VR1 acts as an integrator of noxious stimuli in mammals.
       ( etc. etc. etc.)
Jordt and Julius assumed that birds express a capsaicin-insensitive
version of VR1.
            ( another snip, snip ... )
So what’s in it for the chili? The original function of any fruit
- including hot peppers - is to attract animal consumers to eat the fruit
and thus disperse the seeds. If chili plants take precautions to
selectively deter mammals, that must mean that mammals are not
adequate for seed dispersal, possibly because they digest the seeds.
A recent study by Tewksbury and Nabhan confirms this suspicion:
they found that seeds of mild chilis no longer germinated after
ingestion by rodents, but germination was unaffected if the seeds had
been eaten by birds. These feeding experiments also confirmed that
rats and mice are cautious in their approach to chilis - they will nibble
on mild ones, but only if they have never had a hot one - whereas birds
show no such inhibitions. It would be interesting to investigate whether
mammals and capsaicin evolved at the same time. Did dinosaurs only
know mild peppers, or is it simply that the chili plants that produce
capsaicin survived better when mammals became their dominant
predators? "
---------------------------------

    ...  wish there was more about the toad thing ...
    anyone having problems with roaming gangs of chile-chomping,
post-dinosauric, predatory pepper toads in their garden ??
    i get all wobbly-legged just pondering those steely-eyed amphibians
plotting their next raid on my habaneros !!!

riiibbbitt
peter g
( dominant predator. for sure. )