title: Prejunctional adrenergic inhibition by aggregating platelets in canine blood vessels.
abstract: 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.
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D003331:Coronary Vessels / Q000502:physiology*; D004285:Dogs; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008719:Methiothepin / Q000494:pharmacology; D009119:Muscle Contraction; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects*; D012501:Saphenous Vein / Q000502:physiology*; D012701:Serotonin / Q000097:blood / Q000494:pharmacology*; D013929:Thromboxane B2 / Q000097:blood
chemical_list: D012701:Serotonin; D013929:Thromboxane B2; D008719:Methiothepin; D009638:Norepinephrine; D010646:Phentolamine