Histamine is a biogenic amine synthesized by the enzyme histidine decarboxylase (Hdc) and used as a neurotransmitter in the central nervous system of Drosophila melanogaster. We are interested in understanding how tissuespecific expression of Hdc is controlled by examining the function of both the Hdc 5’-UTR (Untranslated region) and 3’-UTR through the regulation of the expression of the reporter gene, eGFP. Initial studies reported here examine the function of the 5’-UTR of the Hdc gene by determining whether eGFP expression can be demonstrated in histaminergic cells of transformant flies containing the pHdc-5’- UTR-eGFP transgene. To determine if all cells expressing eGFP in these transformants are also histaminergic, examination of histamine- stained CNS preparations from various developmental stages of transformant flies was conducted and analyzed using fluorescence microscopy. Results indicate that many histaminergic cells appear to express eGFP as well. These results indicate that the 5’-UTR region of Hdc can induce expression of eGFP in centrally located histamine-containing neurons. Differences in the level of expression of eGFP observed between cell types and developmental stages suggest that the 3’-UTR of Hdc may still be required for complete expression. Since the co-localization of eGFP and histamine in cells has been achieved, new areas of research may now be conducted to investigate the function of histaminergic cells in culture, leading to a better understanding of the role that histamine cells play in the central nervous system.