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ArticlesCopyright © 1975 by American Association for the Advancement of Science
Ultrasensitive chemosensory responses by a protozoan to epinephrine and other neurochemicals
A behavioral assay was developed based on differential tendency of a protozoan to attach to an agar gel containing the test substance. The heterotrophic marine dinoflagellate Crypthecodinium (Gyrodinium) cohnii responded negatively (less tendency to attach) to epinephrine at concentrations above 5 X 10(-15)M and to norepinephrine at concentrations above 5 X 10(-9)M. Response to choline as choline H2 citrate, choline bitartrate, and choline chloride was negative above 10(-7)M, but response to the choline analog carbachol was positve (greater tendency to attach) in the range 5 X 10(-6) to 5 X 10(-4)M. Other responses to neurochemicals at comparable concentrations were: dopa, betaine, and glycine--positive; L-glutamic acid, tryptophan, putrescine, and taurine--negative. Serotonin was inert, responses to tyrosine and gamma-aminobutyric acid were variable, and phenylalanine (6 X 10(-3)M) and 5-hydroxytryptophan (5 X 10(-4)M) were negative only at the highest concentrations tested.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)
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