Electrophysiological and Behavioral Mechanisms of Caenorhabditis Elegans Feeding

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Title: Electrophysiological and Behavioral Mechanisms of Caenorhabditis Elegans Feeding
Author: Shtonda, Boris Borisovich
Abstract: The nematode (roundworm ) Caenorhabditis elegans lives in soil and eats bacteria . Its feeding organ is a neuromuscular pump called the pharynx . First , I developed a voltage clamp preparation for the pharynx and recorded native ionic current in the pharyngeal muscle . I showed that a T -type Ca channel CCA -1 , an L -type Ca channel EGL -19 and a potassium channel EXP -2 shape pharyngeal action potentials . CCA -1 works in the pharyngeal muscle to boost its response to neurotransmission from the MC pharyngeal neuron . Next , EXP -2 is not an inward rectifier in the pharynx ; it generates large currents upon hyperpolarization and has nearly linear voltage dependence . Finally , the pharynx adapts to the loss of MC excitatory inputs by raising its resting membrane potential , which makes it more excitable . Second , I studied food seeking and food preference behaviors in C .elegans . In the laboratory , C .elegans is routinely kept on plates seeded with E .coli , and it is not known how worms behave in an environment where diverse food is available . I identified additional food sources , such as Bacillus megaterium , Comamonas sp . , and Bacillus simplex , and showed that bacterial food varies in quality . C .elegans hunts for the food of higher quality , the one that better supports growth . This seeking activity is further enhanced in animals that have already experienced good food . Next , the food regulates C .elegans locomotion , particularly the equilibrium between two locomotion modes , known as roaming and dwelling . On good food , dwelling is more common , on poor food , roaming is predominant . The normal balance between these states is essential for the food seeking behavior . In ttx -3 and osm -6 mutants the food -dependent equilibrium between locomotion states is impaired : worms tend to spend less time roaming on poor food . ttx -3 defects are partially reproduced by laser ablation of AIY interneurons , suggesting that AIY functions to inhibit the roaming -to -dwelling transition and to extend food -seeking periods . On the other hand , tax -6 mutants show increased roaming even on high quality food . tax -6 , osm -6 and ttx -3 mutants are defective in food choice behavior . C .elegans may serve as a new system to uncover mechanisms that enable animals to find high quality food in diverse environments .
URI: http : / /hdl .handle .net /2152 .5 /532
Date: 2004-12-15


Electrophysiological and Behavioral Mechanisms of Caenorhabditis Elegans Feeding. Graduate School of Biomedical Sciences. Available electronically from http : / /hdl .handle .net /2152 .5 /532 .

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