AJP - Heart and Circulatory Physiology, Vol 249, Issue 3 685-H689, Copyright © 1985 by American Physiological Society
Prejunctional adrenergic inhibition by aggregating platelets in canine blood vessels
R. R. Lorenz and P. M. Vanhoutte
Experiments were performed to determine the effect of aggregating platelets
on adrenergic neurotransmission. Rings of canine saphenous veins and left
circumflex coronary arteries were incubated with [3H]norepinephrine and
suspended for superfusion. Aggregating platelets and exogenous
5-hydroxytryptamine decreased the overflow of [3H]norepinephrine evoked by
electrical stimulation of the adrenergic nerve endings. The reduction of
transmitter overflow caused by 5-hydroxytryptamine was prevented by the
serotonergic antagonist methiothepin in a concentration that did not
significantly affect the release of 5-hydroxytryptamine or thromboxane B2
from the aggregating platelets. Methiothepin decreased but did not abolish
the inhibitory effect of aggregating platelets on neurotransmitter
overflow. These experiments demonstrate that 5-hydroxytryptamine and other
substances released from aggregating platelets can exert prejunctional
inhibition of adrenergic neurotransmission in isolated blood vessels.
