OLFACTORY, VOMERONASAL AND TRIGEMINAL 

 RECEPTOR RESPONSES TO ODORANTS 



Don Tucker* 



Several years ago Beidler and Tucker (1955) discovered that one could 

 record activity from the primary olfactory nerve in response to odorous 

 stimuli. Typically, a small strand of the nerve is freed and cut centrally so 

 as to form a peripherally directed twig, which is then placed on two Pt-Ir 

 wire electrodes. Ringer's solution is replaced with mineral oil and dif- 

 ferential recording employed. It is true that considerable practice is 

 required for successful dissection. But for those who use electrical record- 

 ing techniques there is an easier method that will demonstrate the nature 

 of the activity recorded. One must remove the investing membranes from 

 a small portion of the bulk of the nerve in a location that permits the 

 physiological solution to be drained off and replaced with oil. Contacting 

 the exposed surface of the nerve with a small electrode often yields sur- 

 prisingly good records. Alternatively, the conducting solution may be left 

 in place and the surface of the nerve contacted or penetrated with a small 

 wire that is insulated except at the tip (Mozell, 1961). As might be expected, 

 however, twigs raised up into oil give a higher signal-to-noise ratio and are 

 stable over long periods of time. 



I would like to mention questions that our research has raised and to 

 submit incidental observations rather than to concentrate on polished 

 results. My hope is that we can encourage electrophysiologists who 

 specialize on the bulb or the nerve or the mucosa to examine the other 

 recording sites, for general familiarity on the part of all will surely work 

 toward our collective benefit. We may note that the major part of this 

 symposium is devoted to gustation and that the taste receptor cell is dis- 

 tinct from the synapsing nerve fiber. There is a tendency to regard the 

 olfactory receptor and nerve fiber as being unique because they are part 

 and parcel of the same cell. But this is also true of the vomeronasal and 

 trigeminal sensory systems. These three nasal sensory systems will be 

 discussed for the domestic rabbit and a land tortoise known as Gopherus 

 polyphenms. 



*This investigation was carried out during successive tenures of a Predoctoral Fellowship 

 (BF-7977) from the National Institute of Neurological Diseases and Blindness and Pre- 

 doctoral (2G-436) and Postdoctoral (2B-5258) Traineeships from the United States Public 

 Health Service. 



45 



