RESPONSES TO ODORANTS 67 



contrast, a small olfactory response to decyl alcohol is usually present. 

 Prominent reflex responses of autonomic fibers distributed to the nose 

 occur in parallehsm with the trigeminal receptor responses, provided that 

 the animal is not too depressed with urethane anesthesia. Trigeminal 

 twigs are obtained from the ethmoidal nerve, which arises from the naso- 

 ciliary nerve within the orbit. At the nasal level the branches of the 

 ethmoidal nerve contain a rich complement of autonomic fibers. There- 

 fore, one may record trigeminal sensory activity from a peripherally directed 

 twig and autonomic motor activity from a centrally directed twig. 



Autonomic Effectors 



We know very little about the autonomic eff'ectors and their role in nasal 

 physiology. Electrical stimulation of the cervical sympathetic nerve 

 commonly causes enhancement of the olfactory response to an odorant 

 (Tucker and Beidler, 1956). In a preparation suitable for viewing the nasal 

 interior, sympathetic stimulation causes blanching of the nasal mucosa 

 and an increase in width of the slit-like passage between the septum and 

 the ethmoturbinates. The widening undoubtedly increases accessibility of 

 odorant to the olfactory receptors. Parasympathetic activation by stimu- 

 lation of the greater superficial petrosal nerve seems to cause more profuse 

 flow of nasal secretions. If the cervical sympathetic nerve is sectioned 

 to prevent sympathetic activity of central origin from appearing at the 

 nasal recording electrodes, presentation of alcohols causes marked increases 

 of parasympathetic activity with trigeminal activation (Fig. 20). 



We had long wondered about the basis for synchronization with respira- 

 tion of the automic activity to the nose. The ongoing level tends to 

 increase with depth of anesthesia and to become more synchronized. With 

 very deep anesthesia the parasympathetic component is highly depressed. 

 We now know that a mucous rattle in the throat can cause autonomic 

 activity synchronized with respiration, thus is indicated a reflex mechanism. 



The ethmoidal nerve site should be of especial interest to students of 

 autonomic nervous system function. Let us suggest, for example, the 

 application of electrophysiological techniques to the study of drug eff*ects. 

 Small branches of the ethmoidal nerve can easily be dissected free and 

 from them may be recorded action potential spikes of individual fibers 

 belonging to both divisions of the autonomic system. The wealth of 

 motor innervation is demonstrated by the oscilloscope tracings shown in 

 Fig. 21, although the records are of inferior quahty. Unfortunately, the 

 film driving mechanism in the camera did not maintain constant speed. 

 The responses shown are far from the maxima, rather the stimulus was 

 adjusted for approximately equal postganglionic bursts from the superior 

 cervical sympathetic ganglion and the sphenopalatine ganglion. The 

 stimulus sites were the cervical sympathetic nerve and the greater super- 



