[Effect of tyramine on the spinal cord afferent link of pressor reflexes]

In anesthetized cats, tyramine application on the dorsal surface of C6-TI spinal cord segments suppressed the pressor components of blood pressure reflexes evoked by radial nerve A sigma or A + C afferent stimulation. Tyramine application on L4-SI spinal cord segments suppressed pressor reflexes to tibial nerve stimulation. Both the degree and the rate of reflex suppression increased with the rise in tyramine concentration from I to 4%. Along with these local effects "distant" tyramine action was demonstrated: pressor reflexes to radial nerve stimulation increased when tyramine was applied on L4-SI segments, but after its application on C6-TI segments pressor reflexes to tibial nerve stimulation increased in some cats, decreased in the other ones, or remained practically unchanged.