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Conditioned Taste Aversion
Kevin Nahler Kevin Nahler
Tony Norton National Geographic
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I. Conditioned Taste Aversion (CTA)
A. Definition
B. Evolutionary Basis
II. CTA at the Organ System Level
A. Brain Stem Activity
B. Role of the Amygdala
III. Molecular Processes Behind CTA
A. CREB
B. c-FosC.Metabotropic Glutamate Receptors
IV. Substances that produce CTA
A. Lithium Chloride
B. Estrogen
C. Thiabendazole
V. Practical Application of CTA
A. Reduction of Livestock and Crop Losses
B. Conservation of Endangered Species and Other Wildlife
C. Drug and Radiation Therapies for Humans
VI. References
Tony Norton
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Conditioned Taste Aversion (CTA) is a form of
associative learning and classical conditioning
in which an animal avoids and acts aversivelyto the taste of a food that has previously been
paired with illness. (Houpt)
Why would such a phenomenon exist innature?
University of FloridaKevin Nahler
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CTA in the Brain Stem (Short Term Memory and Physiological Response)
Brain stem receives input regarding internalconditions in the body; controls involuntary functions
such as digestion, respiration, and circulation; food
preference learning takes place at least partially in the
brain stem
The Nucleus of the Solitary Tract in the medulla
(emetic center) junction of nerves from tongue thatbring taste sensations with the vagus nerve that
brings sensory impulses from the upper GI tract
If digestion and absorption results in nutrients being
replenished in the body, the brain remembers that
food choice as a good one; if food contains poison of
some kind, the brain stem receives signals from thedigestive tract and send signals back that result in
vomiting and other detoxifying processes
The brain remembers the external cues surrounding
the food that produced the illness and will not
tolerate the scent and taste of that food in the future
(taste-illness pairing also results in association of non-taste cues such as scent or appearance of food)
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CTA in the Amygdala and Gustatory Cortex
(Long Term Memory and Behavioral Response)
The gustatory cortex (in the
cerebrum) processes and retains
memory of taste while the amygdala
plays a crucial role in the integration
and expression of CTA behavior (i.e.the formation of long term memories
and patterns of behavior of CTA)
The memory of CTA produced in the
brain stem only remains effective if
certain genes are expressed in theamygdala
The amygdala has been shown to be
responsible for many types of aversive
and emotional learning
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Molecular Mechanisms of CTA cAMP Response Element-Binding Protein (CREB)
cAMP = second messenger that regulates ion channels(Ca2+) (among other functions)
CREB = transcription factor that binds to cAMP responseelements on DNA to increase or decrease transcription
Genes regulated by cAMP Response Elements (CRE-regulated genes) produce long term changes in theamygdala that enable retention of CTA-relevantinformation
Must be functioning properly for long term CTA memoryto be produced (does not affect short term memory orretrieval of long term memory once it has been formed)
c-Fos Proto-oncogene; transcription factor; immediate early
gene family
Among other functions, c-Fos controls genes that controlsome immune responses (c-Fos genes are expressed aftersensory stimulation, such as light exposure, food intake, ortoxin intake)
c-Fos-like immune (c-FLI) proteins were used todemonstrate the relationship between c-Fos and CTA (i.e.ingestion of LiCl resulted in expression of c-Fos)
c-Fos is found in brain tissue during all CTA responses
Metabotropic Glutamate Receptors (mGluRs) Affect second messengers and ion channels via G-proteins
mGluR7 (one of eight subtypes of mGluRs) is expressed inthe amygdala, among other areas of the central nervoussystem (localized at presynaptic axon terminals); plays arole in amygdala-dependent averse responses; coupledwith inhibition of cAMP cascade
mGluR7 must be functioning properly for CTA to occur
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Some CTA-inducing CompoundsLithium Chloride (LiCl)Naturally occuring salt
Produces a strong, long-lasting CTA
EPA has found some potentially negative environmental
impacts associated with use in untargeted baits
Estrogen (estradiol) (C18H24O2)Includes both naturally occurring and synthetic hormones
Produces the strongest, longest-lasting CTA
Because it is a hormone, its use may affect development
and reproduction in some vertebrates
Thiabendazole (TBZ) (C10H7N3S)Has also been used as an anti-fungal, a preservative food
additive, and a chelating agent to treat heavy metal
poisoning
Produces moderate CTA with minimal side effects
May be a safe alternative to other compounds but more
testing is needed
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Practical Applications of CTA
Reduction of Livestock and Crop Losses
Economic impact
Socio-political impact
Human health impact
Conservation of Endangered Species and OtherWildlife
Reduced depredation and crop destructionresult in greater survival and reproductive ratesfor wildlife (particularly critical for endangeredand threatened species)
Drug and Radiation Therapies for Humans
Understanding CTA could lead to improvedtreatments for a variety of diseases whosetreatments currently involve debilitating sideeffects
Tony Norton
afssa.fr
fluofarma.com
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References "Amygdala." Wikipedia, The Free Encyclopedia. 5 Dec 2008, 08:29 UTC. 10 Dec 2008
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Gill, Elaine L., Anne Whiterow, and David P. Cowan. A Comparative Assessment of Potential Conditioned Taste
Aversion Agents for Vertebrate Management. Applied Animal Behaviour Science. Volume 67, Issue 3, April 3,
2000, pp. 229-240.
Houpt, Thomas A., et al. Increased c-fos Expression in Nucleus of the Solitary Tract Correlated with Conditioned
Taste Aversion to Sucrose in Rats. Neuroscience Letters. Issue 172, February 18, 1994, pp. 1-5.
Lamprecht, Raphael, and Yadin Dudai. Transient Expression of c-fos in Rat Amygdala During Training is Required
for Encoding Conditioned Taste Aversion Memory. Learning Memory. Volume 3, 1996, pp. 31-41.
Lamprecht, Raphael, Shoshi Hazvi, and Yadin Dudai. cAMP Response Element-Binding Protein in the Amygdala is
Required for Long- but not Short-Term Conditioned Taste Aversion Memory. The Journal of Neuroscience.
Volume 17, Number 21, Issue of November 1, 1997, pp. 8443-8450.
Massei, Giovanna, and David P. Cowan. Strength and Persistence of Conditioned Taste Aversion in Rats:
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pp. 249-260.
Masugi, Miwako, et al. Metabotropic Glutamate Receptor Subtype 7 Ablation Causes Deficit in Fear Response
and Conditioned Taste Aversion. The Journal of Neuroscience. Volume 19, Number 3, Issue of February 1, 1999,
pp. 955-963.
Nicolaus, Lowell. Predation Politics: The Sad Story of Wolves, Conditioned Taste Aversion, and the Wildlife
Management Hierarchy. [Online] Available http://www.conditionedtasteaversion.net/index.html, March 2008.
"Solitary nucleus." Wikipedia, The Free Encyclopedia. 20 Aug 2008, 05:25 UTC. 10 Dec 2008
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Ternent, M.A., and D.L. Garshelis. Taste Aversion Conditioning to Reduce Nuisance Activity by Black Bears in a
Minnesota Military Reservation. Wildlife Society Bulletin. Volume 27, Number 3, 1999, pp. 720-728.
Images of CTA-inducing compounds and cAMP downloaded from Wikipedia; images of brain found using Google
image search