Fresh-water Fish Chemoreceptors Responsive to Dilute Solutions of Electrolytes

I N T R O D U C T I O N The palatal chemoreceptors of the carp display a rather peculiar type of response to varying concentrations of electrolytes (Konishi and Niwa, 1964). Dilute solutions of salts, especially those with polyvalent anions such as Na3citrate and Na 2 HP04 , produced strong responses. However, an increase in concentration depressed receptor activity, although the activity increased again at much higher concentrations. The response vs. concentration curve (concentration curve) obtained by recording an integrated response therefore displayed an inverse S-shape. The application of distilled water, immediately after the receptor had been irrigated by a salt solution at the concentration at which chemoreceptor activity was depressed, elicited a remarkable stimulatory response (distilled water effect (DWE)). Such an effect was not observed