MONOAMINE UPTAKE IN INSECT SYNAPTOSOMAL PREPARATIONS

Biochemical studies of mammalian synaptosomal nerve fractions indicate the existence of multiple transporter proteins important for the term ination of synaptic transmission by each of several monoamines. In ins ects, however, data on monoamine uptake has been limited to the study of whole tissue preparations, making it unclear whether neuronal (as o pposed to glial) uptake is a significant mechanism in the insect. The present experiments elucidate the difficulties that have limited the u se of insect synaptosomal preparations for characterizing amine reupta ke. Key procedural improvements, including the utilization of carrier protein for tracer separation and the use of receptor antagonists to d ecrease non-specific membrane binding are described. With these and ot her modifications, reproducible sodium-dependent and cocaine-inhibitab le dopamine and octopamine uptake are described in synaptosomal-contai ning preparations from insect brain and ganglia. These studies therefo re support the existence of specific Na+-dependent uptake mechanisms i n insect neurons.