Blood pressure reflexes to stimulation of tibial nerve a fibers in mesencephalic and bulbar cats

Autor: V. M. Khayutin, E. V. Lukoshkova, Yu. B. Gailans
Rok vydání: 1977
Předmět:
Zdroj: Bulletin of Experimental Biology and Medicine. 84:1381-1385
ISSN: 1573-8221
0007-4888
Popis: The role of the various subgroups of A fibers of the tibial nerve (pulse frequency of electrical stimulation 10/sec) in the formation of reflex changes in blood pressure (BP) was investigated in unanesthetized cats with total transection of the brain stem at the level of the pontomedullary junction (bulbar animals) or at the rostral border of the mesencephalon (mesencaphalic animals), and also in anesthetized cats with an intact brain. The lowest thresholds for the reflexes were found in anesthetized animals with an intact brain, the highest in bulbar cats. Excitation of A fibers in anesthetized cats with an intact brain evoked only depressor reflexes. In some bulbar and mesencephalic animals only pressor reflexes appeared. In the experiments of this group excitation of fibers with a conduction velocity of over 15 m/sec in mesencephalic cats evoked reflexes of near maximal strengths, whereas in bulbar cats excitation of thinner A fibers also was necessary. In unanesthetized animals disconnection of the suprabulbar structures thus lowers the sensitivity of the central mechanisms of vasomotor regulation to impulses in lowthreshold A fibers. No such effect was found in another group of experiments in which depressor reflexes appeard in response to stimulation of fast-conducting A fibers only. In these experiments, if slower A fibers also were stimulated, the reflexes became pressor but the difference between their magnitude in the bulbar and mesencephalic cats was not signicant.
Databáze: OpenAIRE
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