| The vestibular system is composed of vestibular receptors, vestibular nerve, vestibular nuclei and the relative projection pathway. The vestibular receptors include the otoliths organ that recept the gravity and the liner accelerative motion, and the crista ampullaris which recept the information of the angle accelerative movement. The vestibular nuclei is the located site of the second neurons which in the upper transmit pathway, and is the key of receiving the vestibular primary afferent, integrating information and projecting efferent to regulate body motions. Altereing velocity of motion, gravity change and the variety of posture or head position, all of these could excite vestibular receptor, modulate body posture, eye-movement, muscle strain so as to maintain the body balance, and as the same time those can rapidly modulating the circulation, respiration and other visceral activity which could keep the stabilization of internal environment. Car sickness, nausea, airsickness and space motion sickness are due to the vestibular system abnormality activity leading the disorder of visceral function. So, it has become one of the focuses that the mechanism of the vestibular system in modulating the cardiovascular activity. The illumination of the mechanism has important academic and practicality significance that to defend and treat various motionsickness, Miniers' syndrome, astronauts' postflight orthostatic intolerance and to the life maintenance of the pilot and the astronaut.Previously research which of vestibular system modulating the cardiovascular activity, find that electronic or natural vestibular stimulate could induce the change of the blood pressure and the pattern of sympathetic nerve discharge. These results indicate that the sympathetic nerve activity were influenced by the vestibular afferent signal, through some pathway. BJ.Yates has brought forward the neural pathway of the vestibular system regulating cardiovascular activity, according to summarize the temporal investigation results respectively in 1992,1995,1996 and 1998. The pathway brought forward in 1998 was that: the otoliths organ - the vestibular nuclei the medulla lateral reticular formation - rVLM - IML- sympathetic nerves. Foundation of the pathway was based on the influence of the vestibular signal to the activity of baroreceptor reflex, and emphasized the effects of the otoliths afferent to the cardiovascular activity. According to the analysis of the former data and the results of the primary experiments, the author considered that there were some problems in the researches of the nerve pathway that the vestibular afferent regulated the cardiovascular activity: (1) Because the sympathetic nerve activity could also be made by the altering velocity rotation obviously. The effect of otoliths afferent to the cardiovascular was emphasized excessively these years, and the effect of semicircular canals ampullae afferent was neglected. (2) The modulation of the vestibular system to cardiovascular activity maybe not only one pathway through baroreceptor reflex, because integrating body exercise and viscera activity to adapt the body temporal requirement , there should be several central parts to participate in, especially the upper center. (3)There is not enough evidence to deny the impact of the vestibular afferent to the parasympathetic nerve activity. (4) Cat was the experimental material in all of above experiments. Animal in different species maybe have different regulating pathway. Therefore, the following pathways were investigated by using tract tracing techniques, immunohistochemist technique and other technique inSprague-Dawley rat in present study. (1) The direct projection from MVe, SpVe to the brainstem cardiovascular regulatory area; (2) The indirect projection from SpVe and MVe to the IML of spinal cord through DPGi in rostral medulla. The result are as follows.l.The direct projection from MVe, SpVe to the brainstem cardiovascular regulatory area.After Phaseolus vulgaris leucoagglutinin (PHA-L) was injected in...
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