Gustatory and olfactory sensitivity to extracts of jack mackerel muscle inyoung yellowtail Seriola quinqueradiata

The stimulatory effects of extract fractions of jack mackerel muscle, obtai ned using anion exchange chromatography, and their components on the gustat ory and olfactory receptors of young yellowtail were investigated by record ing electrical responses from the palatal taste nerve and the olfactory bul b. Ultrafiltrate (mol. wt. cut-off, 10,000 Da) of the muscle extract (FE) s timulated both chemosensory systems. FE was treated with a DEAE-Sephadex A- 25 column (pH 5.5). The olfactory receptors showed a high sensitivity to bo th the adsorbate and non-adsorbate from the DEAE-Sephadex column. Their thr esholds in the olfactory bulb response were around 10(-5) and 10(-8) of the original concentration, respectively. Those in the gustatory nerve respons e were 10(-4) and 10(-2). Amino acids were highly effective for the olfacto ry receptors. The threshold of L-glutamine was around 10(-8) M. 5'-Inosinic acid and L-lactic acid were more effective for the gustatory receptors tha n for the olfactory receptors; their thresholds for the former were 10(-4) M and 10(-6) M, while those for the latter were 10(-3) M and above 10(-3) M . These findings suggest that the gustatory receptors are involved in discr iminating food items during feeding and that the olfactory receptors may de tect foods at some distance. (C) 2000 Elsevier Science B.V. All rights rese rved.