Inhalational and local anesthetics reduce tactile and thermal responses in mimosa pudica.

PURPOSE: In reaction to a variety of stimuli, the sensitive plant mimosa pudica closes its leaflets and drops its stems. The objective was to investigate the effects of anaesthetics on the reaction of mimosa pudica to a variety of stimuli.
METHODS: The ability of the plants leaflets to close (n=4, Q5min.) was tested after exposure to halothane 4% and 6L x min(-1) O2, or 6L x min(-1) O2. Lidocaine 2% or vehicle were administered through the roots, cut stems, or sprayed on the leaves (n=4). The test consisted of stimulating the leaves, by burning their tips (lidocaine experiments) or touching them with a metal rod (halothane); the closing of the leaflets, or the lack thereof was then observed.
RESULTS: After 15 min exposure to halothane, the mimosas had slow and incomplete reactions to tactile stimulation. Following 20 min exposure, the plants had no visible reaction to touch, a stimulus which would normally cause the collapse of the entire leaf. After one minute, mimosa leaves sprayed with lidocaine had no reaction to a lit match being touched to the tips of the leaves, contrary to the control in which the leaves collapsed completely. After exposure to lidocaine 2% through the roots and cut stems, the mimosa's reactivity gradually decreased; after four hours the leaves were insensitive or had slow reaction to tactile stimuli.
CONCLUSIONS: Inhalational and local anesthetics inhibited motor mechanisms of the mimosa plant. This may be a model to elucidate the mechanisms of action of anesthetics.