Differential effects of local anesthetics and propranolol on arachidonic acid and adenosine 5'-diphosphate-induced...

The effects of several local anesthetics and propranolol, a beta receptor antagonist with local anesthetic activity, on adenosine 5'-diphosphate (ADP) and arachidonic acid (AA)-induced aggregation were studied in rabbit platelets. Platelet-rich plasma (PRP) was obtained from rabbits anesthetized with pentobarbital and changes in turbidity of PRP were measured with an aggregometer. Inhibition of platelet aggregation by the local anesthetics was expressed as the percent change in rate of aggregation from control value. Dibucaine was the most potent inhibitor of both AA- and ADP-induced aggregation. This inhibition was sensitive to external calcium concentration. In terms of potency dibucane > tetracine > lidocaine in inhibiting AA- and ADP-induced aggregation. Procaine was more effective against AA- than ADP-induced aggregation. Propanolol was comparable to the more potent local anesthetics. These data show that local anesthetics and propranolol inhibit both AA- and ADP-induced platelet aggregation and suggest that the mechanism of action is non-specific in nature.