Sex-specific risk of cardiovascular disease and cognitive decline: pregnancy and menopause
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.