CHEMORECEPTOR MECHANISMS 31 



With regard to the use of the tracers, we have also considered the possibility 

 that we are somewhat pessimistic in our outlook, maybe unjustifiably so, be- 

 cause frankly, I do not know very much about the technique involved. I have 

 wondered in my own mind whether it would be possible to get the answer from 

 tracers as to whether it washes away or not. Maybe you can tell us whether 

 in small preparations of this sort, where we are working in micron dimensions, 

 this method would help us in telling whether the stimulating substance is part 

 of the receptor or can be washed away. 



Dr. Morales: I do not know anything about tracer technique, either. I 

 would propose this as a logical point because, you see, if you start from the 

 premise that you want a very small amount of something to do a lot then the 

 idea of having this be an activator or inhibitor is much more attractive than 

 to have a substrate. If the thing is incorporated and cannot be washed away, 

 then the chances are that this is really participating and being used up in the 

 reaction. 



Dr. Dethier: I agree fully and it is just a question of whether it is technically 

 possible or not. If it is, then, we shall sometime get going on it. 



Dr. Alex Rich (National Institute of Mental Health) : I was a little puzzled 

 by your statement about the fact that salts could reach a threshold concen- 

 tration whereby sugars would not elicit a response. Can you do vice versa, or 

 not? Apparently one of these fibers is the fiber which is responding to the salt 

 and one to the sugar; isn't it rather bizarre that the two are in such unbalance? 



The second question has to do with the fact that there is no competitive in- 

 hibition with sugars. Now, this puts the sugars, as you mentioned, in a class 

 quite by themselves. Does this literally mean that if you have a large amount 

 of sugar which has no response at all and put it into a solution with a small 

 amount of sugar which has a response that you will still get a response? Is it 

 that type of experiment? 



Dr. Dethier: If I may answer your second question first; when we put a 

 small amount of the stimulating sugar with a large amount of the non-stimu- 

 lating sugar, the only effect we get is one which can be satisfactorily accounted 

 for on a dilution basis. 



Dr. Rich: You mean the response is the same as the non-responding sugar, 

 perhaps? 



Dr. Dethier: Yes, unless the small amount of stimulating sugar which is 

 incorporated is present in threshold quantities. We have been unable to demon- 

 strate any competitive inhibitions. 



Now in answer to your first question, one can prevent the salt response by 

 adding sugar and the sugar response by adding salt. However, a concentration 

 of salt can be reached beyond which no amount of sugar can stop it. In other 

 words, when one is working with maxima of the two available compounds the 

 salt takes over. Now, this is not as strange as it may seem, because we are 



