The Effect of Reserpine on Aggregation of Avian Thrombocytes

Avian nucleated thrombocytes are aggregated by acid-soluble collagen, and serotonin (5-hydroxytryptamine) is released from the thrombocytes during the process of aggregation. The action of collagen is inhibited by aspirin and methysergide, a serotonin antagonist. Exogenous serotonin can also induce aggregation. These observations suggest that serotonin, which has been shown to be stored in avian thrombocytes, acts similar to released ADP in mammalian platelets.

Measurement of serotonin content in the blood of Peking ducks (Anas platyrhynchos) which had been given reserpine (3 mg/kg, blood withdrawn 20 hours after injection) showed that the serotonin content of whole blood and thrombocyte-rich-plasma fell to approximately 90 percent of the control level. Analysis of aggregation of thrombocytes from control and reserpinized ducks showed that reserpinization markedly decreased aggregation induced by collagen, while it enhanced aggregation induced by serotonin. These results are consistent with the concept of released serotonin playing a role in thrombocyte aggregation.

(Supported by a grant from National Heart and Lung Institute HE 10002.)