Abstract
The wasp Ampulex compressa injects venom directly into the prothoracic ganglion of its cockroach host to induce a transient paralysis of the front legs. To identify the biochemical basis for this paralysis, we separated venom components according to molecular size and tested fractions for inhibition of synaptic transmission at the cockroach cercal-giant synapse. Only fractions in the low molecular weight range (<2 kDa) caused synaptic block. Dabsylation of venom components and analysis by HPLC and MALDI-TOF-MS revealed high levels of GABA (25 mM), and its receptor agonists beta-alanine (18 mM), and taurine (9 mM) in the active fractions. Each component produces transient block of synaptic transmission at the cercal-giant synapse and block of efferent motor output from the prothoracic ganglion, which mimics effects produced by injection of whole venom. Whole venom evokes picrotoxin-sensitive chloride currents in cockroach central neurons, consistent with a GABAergic action. Together these data demonstrate that Ampulex utilizes GABAergic chloride channel activation as a strategy for central synaptic block to induce transient and focal leg paralysis in its host.
Copyright 2006 Wiley Periodicals, Inc.
Publication types
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Animals
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Cells, Cultured
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Central Nervous System / cytology
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Central Nervous System / drug effects*
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Central Nervous System / metabolism
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Chloride Channel Agonists*
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Chloride Channels / metabolism
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Extremities / innervation
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Extremities / physiopathology
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Female
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GABA Antagonists / pharmacology
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Ganglia, Invertebrate / cytology
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Ganglia, Invertebrate / drug effects
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Ganglia, Invertebrate / metabolism
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Host-Parasite Interactions / physiology
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Interneurons / cytology
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Interneurons / drug effects
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Interneurons / metabolism
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Mechanoreceptors / cytology
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Mechanoreceptors / drug effects
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Mechanoreceptors / physiology
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Neural Inhibition / drug effects
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Neural Inhibition / physiology
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Neurons, Afferent / cytology
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Neurons, Afferent / drug effects
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Neurons, Afferent / metabolism
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Paralysis / chemically induced*
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Paralysis / metabolism
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Paralysis / physiopathology
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Parasites / physiology
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Periplaneta / cytology
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Periplaneta / drug effects*
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Periplaneta / metabolism
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Synapses / drug effects
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Synapses / metabolism
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Synaptic Transmission / drug effects*
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Synaptic Transmission / physiology
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Taurine / metabolism
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Taurine / pharmacology
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Wasp Venoms / chemistry
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Wasp Venoms / pharmacology*
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Wasps / physiology
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beta-Alanine / metabolism
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beta-Alanine / pharmacology
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gamma-Aminobutyric Acid / metabolism
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gamma-Aminobutyric Acid / pharmacology
Substances
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Chloride Channel Agonists
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Chloride Channels
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GABA Antagonists
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Wasp Venoms
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beta-Alanine
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Taurine
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gamma-Aminobutyric Acid