The Role Of The Raphe Nuclei Of The Rostral Medulla Oblongata And Caudal Pons In Cardiovascular Regulation In The Rabbit (blood Pressure, Baroreceptor Reflex, Heart Rate, Stimulation, Defence Reaction)

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Doctor of Philosophy (Ph.D.)


The portions of the nuclei raphe obscurus, pallidus and magnus, which are located in the rostral medulla and caudal pons, were stimulated electrically while recording heart rate and blood pressure. Stimulation of the dorsal raphe obscurus led to a pressor response accompanied by tachycardia. A pressor/bradycardia response was elicited from the ventral nucelus raphe obscurus, pallidus and magnus. Chemical stimulation experiments provided evidence that cell bodies mediate the pressor/tachycardia response. The results of sino-aortic denervation experiments and chemical blockade experiments revealed the involvement of the vasomotor limb of the baroreflex in the pressor/bradycardia response and the cardiomotor limb of the baroreflex in the pressor/tachycardia response. Electrical stimulation of the raphe after a post-collicular transection suggested the involvement of neural structures rostral to the pons in the pressor/bradycardia response but not the pressor/tachycardia response.Histochemical and electrophysiological mapping studies indicate that the raphe nuclei project to the intermediolateral cell column of the spinal cord, and receive a projection from the periaqueductal grey of the midbrain.


Biology, Animal Physiology

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