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.
D006916:5-Hydroxytryptophan; D000818:Animals; D001622:Betaine / Q000494:pharmacology; D002217:Carbachol; D002628:Chemoreceptor Cells / Q000502:physiology; D002633:Chemotaxis; D002794:Choline / Q000031:analogs & derivatives; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine; D056890:Eukaryota / Q000502:physiology*; D005971:Glutamates; D005998:Glycine; D009638:Norepinephrine; D010649:Phenylalanine; D011700:Putrescine; D012701:Serotonin; D013654:Taurine; D014364:Tryptophan
D005971:Glutamates; D013654:Taurine; D012701:Serotonin; D001622:Betaine; D010649:Phenylalanine; D014364:Tryptophan; D002217:Carbachol; D006916:5-Hydroxytryptophan; D002794:Choline; D005998:Glycine; D011700:Putrescine; D009638:Norepinephrine; D004837:Epinephrine