For quinolizidine alkaloids (QA) the major molecular targets and the likely modes of action were identified. These alkaloids modulate nicotinic and muscarinic acetylcholine receptors and inhibit Na+/K+ channels. These findings can explain the toxic and pharmacological effects of QA in insects, vertebrates and other organisms. The experimental data provide a solid base to infer the function of QA as defense compounds against herbivores, microorganisms and competing plants. Field data with alkaloid-rich and alkaloid-free lupins clearly show that quinolizidine alkaloids are, indeed, the crucial factor controlling herbivory under natural conditions.

© 2004 by CRC Press LLC

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