A fundamental characteristic of the nervous system is the modification of function in response to a number of stimuli. Neurotransmitters are molecules responsible for communication in the nervous system; therefore, regulation of neurotransmitter synthesis is an important aspect of neural modification. Examples of short- and long-term regulation of neurotransmitter synthesis are numerous, but in many cases the underlying mechanisms are not understood. Tyramine-beta-hydroxylase is the decisive enzyme required for the synthesis of octopamine, a transmitter of insects. In insects that undergo diurnal as well as developmental changes of their nervous system, octopamine and Tyramine-beta-hydroxylase are not static but vary in both short- and long-term cycles. The aim of this study is to investigate the mechanism of these changes in a simple, model nervous system. Molecular probes of Tyramine-beta-hydroxylase will be developed by purifying and sequencing the enzyme for the development of antibodies to the enzyme. The molecular basis of its regulation will be determined by biochemical kinetic analysis, enzyme activity and changes that occur during the diurnal cycle and during development. The results of these studies will contribute to our understanding of the mechanism that regulate neurotransmitter synthesis.