Physiological Evidence for the Discrimination of L-Arginine From Structural Analogues by the Zebrafish Olfactory System

• Published in: Journal of neurophysiology Vol. 82; no. 6; pp. 3160 - 3167
• Main Authors: Lipschitz, D. L, Michel, W. C
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01.12.1999
• Subjects: Adaptation, Physiological - physiology; Animals; Arginine - analogs & derivatives; Arginine - pharmacology; Danio rerio; Discrimination (Psychology) - physiology; Electrophysiology; Female; Freshwater; Image Processing, Computer-Assisted; Immunohistochemistry; Male; Odorants; Olfactory Receptor Neurons - physiology; Smell - physiology; Structure-Activity Relationship; Zebrafish
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.1999.82.6.3160

Department of Physiology, University of Utah School of Medicine, Salt Lake City, Utah 84108-1270 Lipschitz, D. L. and W. C. Michel. Physiological Evidence for the Discrimination of L- Arginine From Structural Analogues by the Zebrafish Olfactory System. J. Neurophysiol. 82: 3160-3167, 1999. Although it is generally assumed that fish are capable of discriminating amino acid odorants on the basis of differences in side-chain structure, less is known about their ability to discriminate amino acids with modifications to -carboxyl and -amino groups. In this study, the ability of the zebrafish olfactory system to detect and presumably discriminate analogues of the basic amino acid Arg was assessed, by using cross-adaptation and activity-dependent labeling techniques. Electrophysiological recordings established that esterification ( L- arginine methyl ester; AME) or deletion (agmatine or amino-4-guanidobutane; AGB) of the -carboxyl group yielded odorants more potent than Arg, whereas deletion of the -amino group ( L- argininic acid; AA) yielded a less potent analogue. In cross-adaptation experiments, no test-competitor odorant combination yielded complete cross-adaptation, suggesting the detection of these Arg analogues by multiple odorant receptors (ORs) with partially nonoverlapping specificities. Activity-dependent immunocytochemical labeling of olfactory receptor neurons supported this conclusion. AGB, an ion-channel-permeant probe (and odorant), labeled 4.9   ± 0.4% ( n = 24) of sensory epithelium, whereas the addition of Arg, 1-ethylguanidine sulfate, L - -amino- -guanidinopropionate, or AME to AGB resulted in a significant elevation of labeling (8-14%). This study provides evidence that the olfactory system has the potential to discriminate among amino acid odorants with modified -carboxyl and -amino groups.