IV 

 SUMMARY 



Robert G. Grenell 



Psychiatric Institute, Medical School, University of Maryland, Baltimore, Md. 



We have attempted in the short course of this symposium to cover 

 several complex and fundamental areas of consideration at various 

 levels of function and integration in the nervous system. To sum- 

 marize all of this material, its implications and the questions to which it gives 

 rise, would be impossible at this time. However, I am somewhat startled to 

 realize how much information and suggestion for future experimentation are 

 revealed by the material presented and discussed in this short day and a half. 



In general, the problems being examined were those at the molecular and 

 grosser biochemical levels which must be considered in an effort to understand 

 the mechanisms — membranal, intraneuronal and interneuronal — whereby 

 stimuli are received, interpreted and transformed into meaningful information- 

 carrying nervous messages which lead to the behavioral responses of the organ- 

 ism. 



The first two papers dealt respectively with "chemical" and "physical" re- 

 ceptors. Dr. Dethier described experiments dealing with the concept of the 

 general action of chemical stimuli. This type of investigation is at one end of the 

 continuum from chemical source to electrical output. Dr. MacNichol, in dis- 

 cussing the electrophysiology of photoreceptors, showed how another type of 

 approach can begin at the electrical output end and work back in the direction 

 of the chemical. These approaches are brought closer together by consideration 

 of, "how in a given receptor, the energy released by the initial mechanical, chem- 

 ical or thermal event is amplified and converted into the kind of information 

 carried by all nerve fibers." This is the "transduction" problem about which we 

 are trying to assess what we know and what leads exist to what we do not know. 

 Several points have been brought out here, however, which would appear to 

 lead to a general hypothesis. It has been demonstrated that very small changes 

 in molecular structure are reflected in pronounced physiological changes. Stereo- 

 isomers have, as Dr. Dethier pointed out, different tastes. It might be added 

 that more recently it has become apparent that steric properties play a funda- 

 mental role in olfaction, as well as in the responses of cerebral motor neurons 



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