Juan M. García-Andrade’s scientific contributions

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Fig. 1. Effect of glutamate agonists bath perfusion on the response of Z. guanensis neurons to microiontophoretic glutamate application. Responses to microiontophoretically applied Glutamate (1 M, 1.5 µA, 200 ms) before (A) and after (B) bath perfusion of kainic acid (KA, 5 mM), quisqualic acid (QA, 0.4 mM) or N-methyl-D-aspartic acid (NMDA, 1 mM). The point indicates the application of glutamate. Calibration: vertical bar = 50 mV, horizontal bar = 2 s.
Fig. 2. Effect of fraction D on a glutamate-induced response of a Z guanensis neuron. Intracellular recordings of the response to microiontophoretically applied glutamate (1 M, 1.5 µA, 200 ms) before (A) and 7 minutes after exposure (B) to fraction D (8 mg/ml). (C) Response to glutamate after 15 min washing recovers up to 60% of control value. The point indicates the application of glutamate. Calibration: vertical bar = 50 mV, horizontal bar = 2 s. (D) Dose-response curve for fraction D on the excitatory phase of the glutamate responses in Z. guanensis neurons. Circles represent the mean values of 2-4 experiments ± SE.
Fig. 3. Fraction D diminishes the basal and mechanical responses of the semicircular canal afferent fibers. (A) Frequency-time plots of the basal and mechanically evoked discharge of semicircular canal afferent neurons. (B) After ejection of 20 µl, 2 mg/ml of fraction D. Gray bars indicate the time during which the preparation is sinusoidally stimulated at 0.2 Hz. (C) Dose-response relationship between fraction D concentration and semicircular canal afferent fibers basal and mechanically evoked electrical activity. Each point represents the mean of at least three tests of a given concentration ± SE. T I M E (min) FRAC. D (mg/ml) 
Fig. 4. Fraction D reduced the excitatory effects of kainic acid (KA) and α-amino-3-hydroxy-5methylisoxasole-4-propionic acid (AMPA) upon the semicircular canal afferent fibers. (A, B) Responses of semicircular canal afferent neurons to the ejection of KA (30 µM, 20 µl) in control conditions and in the presence of fraction D (2 mg/ml) respectively. (C, D) Similar experiment using AMPA (300 µM, 20 µl). 
Antagonism of glutamate receptors by a chromatographic fraction from the exudate of the sea anemone Phyllactis flosculifera
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May 1996

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Juan M. García-Andrade

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In the search for new glutamate antagonists it seems promising to characterize the effects of venom from invertebrates that prey mainly on crustaceans. In this work, the exudate of the sea anemone Phyllactis flosculifera was used as a source of this type of compound. The action of chromatographic fraction D from P. flosculifera was tested upon microion-tophoretically evoked glutamate responses in intracellular recordings from central neurons of the land snail Zachrysia guanensis. Bath application of fraction D (2-8 mg/ml, n = 13) diminished both the excitatory and the inhibitory components of glutamate agonists in Z. guanensis neurons; this action was dose-dependent and partially reversible. Fraction D actions were also tested in the multiunit spontaneous and mechanically evoked responses of the glutamatergic junction between hair cells and afferent neurons of the axolotl Ambystoma tigrinum. Pressure ejection of fraction D in concentrations ranging from 0.5 to 2 mg/ml (n = 9) decreased the spontaneous and mechanically evoked activity of semicircular canal afferent neurons and the responses evoked by kainic acid and alpha-amino-3-hydroxy-5-methylisoxasole-4-propionic acid. This action was also dose-dependent and partially reversible. These results indicate that fraction D acts as a glutamate receptor antagonist in snail and amphibian neurons. Further studies are required to characterize the active compounds responsible for this action and its specificity upon the subtypes of glutamate receptors.

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... Over the past several decades, various impacts of sea anemone venoms on glutamate have been documented. It was reported that the application of fraction D, derived from the sea anemone Actinostella flosculifera (Le Sueur, 1817) = (Phyllactis flosculifera), led to a reduction in the glutamatergic response (at concentrations of 2-8 mg/mL) in neurons of Z. guanensis [27]. This effect was found to be dose-dependent and could be partially reversed within approximately 30 min after washing. ...

Reference:

Effect of Crude Extract from the Sea Anemone Bunodeopsis globulifera on Voltage-Gated Ion Channels from Central and Peripheral Murine Nervous Systems
Antagonism of glutamate receptors by a chromatographic fraction from the exudate of the sea anemone Phyllactis flosculifera

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