Abstract: Slowdown in heart rate and rising of arterial blood pressure were successfully induced by stimulating the nasal mucous membrane with ammonia vapour in rabbits with its respiration kept artificially and immobilized by the use of relaxant. For convenience, cardiovascular responses to ammonia is abbreviated to CVRA. In one experiment, bilateral cervical vagotomy reduced markedly the extent of the bradycardiac reaction of CVRA, while the hypertensive change of CVRA remained unaltered after the same operation. The fact indicates that in CVRA, change of the heart rate and that of blood pressure are originally on their own and resulted from a specific integration action of vagal and sympathetic systems. In another experiment, it was found that stimulation of the cent- ral end of the cervical or subdiaphragmatic vagus give rise to an inhibitory effect on CVRA. But differing from this, enhacement of CVRA could be attende with stimulatin the depressot nerve. No effects on CVRA were observed, whend the superior or recurrent laryngeal nerves were stimulated. Thus, different afferent components of vagal system are varied in relation to CVRA. As to the action of general anesthesia. It has been found that anesthetic effects on CVR A differ from that on the depressor reflex, While both the cardiac and vascular reactions in the former were weakened conspicuously under the action of urethan, only the cardiac reaction in the latter was affected. The study has led to the conclusion that different components of the vagal and sympathetic systems have different susceptibility to general anesthesia, and their substantial effects are flexible, determined by their exciting functional states.

Key words: vagus nerve, ammonia stimulation, heart rate, blood pressure, rabbit