Figure 2. Amino acid-induced changes in calcium-dependent fluorescence of three individual ORNs in a mucosa slice.

A, time course of [Ca²⁺]_i transients of ORN 1 (see Fig. 1B) evoked by the application of amino acids. The traces show responses to the

mixture of 19 amino acids (AA), to the mixture of short chain neutral amino acids (SCN) and to L-glycine. No response to the mixtures of the long chain neutral (LCN), the basic (BAS), the aromatic (AROM) and the acidic (ACID) amino acids. No response to the remaining single amino acids of the SCN mixture. B, ORN 2 (see Fig. 1B) responded to the mixture of AA, the mixture of LCN, to L-methionine and, though slightly weaker, to L-isoleucine, the mixture of SCN, to L-alanine, the mixture of BAS and to L-arginine. No response to the mixtures AROM or ACID, nor to the remaining single amino acids of the responsive groups. C, ORN 3 (see Fig. 1B) responded to the mixtures of AA and LCN; to L-leucine and L-methionine the mixture of SCN; to L-cysteine, L-alanine and L-threonine the mixture of BAS; to L-arginine and, though slightly weaker, to L-histidine the mixture of AROM and to L-tryptophan. No response to the ACID mixture, nor to the remaining single amino acids of the responsive mixtures. All amino acids were applied at a concentration of 200 μM.