West Coast Worm Meeting Abstracts - Caenorhabditis elegans ...

STATE-DEPENDENT LEARNING IN C. ELEGANS.
Jill C. Bettinger, Steven L. McIntire
Gallo Center and Program in Biological Sciences, Department of Neurology, UCSF
The execution of learned behaviors may be triggered by contextual information, consisting of
environmental cues or the internal state of the organism. State-dependent learning refers to the ability of
an organism to more effectively execute learned behaviors if the organism experiences internal contextual
influences similar to those experienced when the learning occurred. Such contexts can be
pharmacologically manipulated by treating with cholinergic compounds, opiates, cocaine and
amphetamines, and with neurodepressants such as ethanol and barbituates 1 . Worms become
intoxicated by ethanol in a manner similar to that of most other organisms tested (see abstracts by A.
Davies and H. Kim, this meeting). We have sought to study the mechanisms of ethanol-induced
state-dependent learning in worms.
Olfactory adaptation in C. elegans is a decrease in the chemotaxis response to an odorant as a result of
prior exposure to the odorant 2 . We demonstrate a form of state-dependent learning in worms by pairing
olfactory adaptation and ethanol administration. Ethanol does not interfere with olfactory adaptation,
however, worms exposed to an odorant while being treated with ethanol will only show subsequent
adaptation to the odorant if ethanol is again administered during chemotaxis testing. If the odorant is
presented without ethanol during testing, the animals behave as naïve animals and therefore fail to alter
their behavior based on their previous experience or prior exposure to the odorant.
Further, we demonstrate that the state-dependent effects of ethanol require normal dopaminergic
function. The dopamine-defective cat-1 4 and cat-2 5 mutants are able to adapt to volatile odorants,
however, they do not show state-dependency when they are adapted to volatile odorants while
intoxicated by ethanol. These results suggest that C. elegans is capable of a form of learning and indicate
a conserved role of dopamine in the modulation of behavioral responses to ethanol.
1 Izquierdo. in Neurobiology of Learning and Memory (eds Lynch, McGaugh, and Wienberger) 333
(Guilford, New York, 1984).
2 Shulz, Sosnik, Ego, Haidarliu and Ahissar (2000) Nature 403, 549, and references therein.
3 Colbert and Bargmann (1995) Neuron 14, 803.
4 Duerr et al. (1999) J. Neuroscience 19, 72.
West Coast Worm Meeting 2000
5 Lints and Emmons (1999) Development 126, 5819.
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