32 V. G. DETHIER 



dealing with two receptors and, to my way of thinking, the addition is taking 

 place in the central nervous system. In those vertebrates which have been 

 studied by electrical methods it has been shown that salt and sugar do not 

 interfere with each other at the peripheral level but at the central level. The 

 business of sweetening a sour drink by adding a lot of sugar to it seems un- 

 doubtedly to be a central nervous system phenomenon. 



Chairman Gerard: Let me toss in something. These two receptors, the two 

 hairs, are they specific, one for salt and one for sugar? Or can each one taste 

 either one? How does the central nervous system know which is being exposed 



to what? 

 Dr. Dethier: There are two fibers in each hair — one fiber for sugar and one 



for the other. 



Chairman Gerard: This is clear. 



Dr. Sidney A. Bernhard (Naval Medical Research Institute) : I would like 

 to question your enzymatic or activator or inhibitor hypothesis from your data 

 on the sugars. If first you examine the data on the salts alone that could equally 

 well be explained just on the basis of binding in itself. That is, all the data 

 indicate that you have an electrostatic binder phenomenon with the salt. 

 Let us assume that with the sugars all one had was a sort of Van der Waals 

 binding, then what one would expect would be that sugars with nearly comple- 

 mentary structures to the site would produce, or would give a positive sensa- 

 tion; whereas, sugars without the complementary site would not. Therefore, 

 you could never find an inhibitor under such a model. Everything which we 

 call a competitive inhibitor would, in fact, taste sweet. 



Dr. Dethier: Yes, I see your point. I think that the only answer would be 

 more experiments. 



Dr. Rich: Apropos of tests and apropos of these experiments, supposing 

 you took a very strongly labeled sugar, both an active one and an inactive one, 

 and put it on the taste bud, then washed it away, and then tested how much of 

 it was bound. It may be that the amount of sugar bound to the receptor sites 

 will be below the threshold of what you can detect with the tracers, but, if you 

 could detect it and you got a difference, then you could account for this par- 

 ticular phenomenon. 



Dr. Dethier: I think that the crucial thing is whether there would be 

 enough to detect. I would simply like to say, with regard to the sugar problem, 

 that aside from preparations in mammals where it may be possible to have a 

 single sugar receptor to play with, and I emphasize the "may"- -in all other 

 preparations we have to deal simultaneously with a receptor which is opposing 

 this in the central nervous system. If we put in, or attempt to put in inhibitors, 

 even if we did get an inhibited reaction we would never know whether the 

 inhibition was peripheral or whether it was in the central nervous system. So 

 that the most informative studies have been those which relate structure and 



