Tyramine-binding by synaptosomes from rat brain: effect of centrally active drugs

Incubation of p-tyramine (TRM) with rat midbrain plus corpus striatum (MB+ CS) crude synaptosomal preparations, under conditions which reduce to a minimum amine uptake, results in appreciable binding of this amine by synaptosomes. This process is inhibited by preincubation with a number of drugs active in the CNS, e.g., chlorpromazine, desipramine, d-amphetamine, and diphenhydramine. Morphine, however, does not affect this binding. The Ki for each one of these compounds, as well as the K association constant and concentration of the binding sites of TRM, were determined. These results suggest a role for TRM in synaptic transmission mechanisms occurring in the nigrostriatal system, a function which could be regulated by a number of substances representing some of the major chemical classes of centrally active drugs (CD).