ON THE ROLE OF VAGI AND SINUS NERVES IN THE REFLEXOGENIC INHIBITION OF SYMPATHETIC DISCHARGES INDUCED BY STROSPESIDE IN CATS

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Abstract
The role of vagi and sinus nerves on the inhibi- tory action of strospeside upon efferent discharges in sympathetic cardiac fibers, were investigated using cats anesthetized with pentobarbital sodium. In vagotomized cats, 20[long dash]30% LD of strospeside produced a bradycardia and an inhibition of efferent discharges in the left postgang-lionic stellate fibers. In cats in which both vagi and both sinus nerves were severed, strospeside neither produced bradycardia, nor inhibited efferent discharges in the left postganglionic stellate fibers. In cats in which only both sinus nerves were severed, 20[long dash]40% LD of strospeside produced a marked bradycardia and an inhibition of efferent discharges in the left postganglionic stellate fibers. From the foregoing results, it is concluded that sinus nerves and vagi are both afferent routes of reflexes by which an inhibition of efferent sympathetic cardiac discharges by strospeside is induced and that the inhibition of sympathetic discharges is considered to be an important extravagal factor of bradycardia produced by strospeside.