The Effect of Peripheral and Central Histamine Deficiency on Courtship Behavior in Drosophila melanogaster. Judith A. Ingles¹, Anthony Hage¹, Shelby Lemke^1,3, Martin G. Burg^1,2. 1) Biomedical Sciences, Grand Valley State University, Allendale, MI; 2) Cell & Molecular Biology, Grand Valley State University, Allendale, MI; 3) Univ. of Michigan Med. School, Univ. of Michigan, Ann Arbor, MI.

   Histamine is a biogenic amine synthesized from L-histidine via a decarboxylation step by the enzyme histidine decarboxylase (HDC). Mutations in the Hdc gene, which disrupt HDC function, have been used to identify the effects of histamine deficiency on a number of behaviors in Drosophila including visual, mechanosensory, and temperature preference behaviors. Histamine has been localized to peripheral sensory receptor cells (photoreceptor and mechanosensory receptor cells) and a small number of central brain neurons. Thus far, it has not been possible to separate the function of the histaminergic neurons in the CNS from that of the PNS, as Hdc mutations eliminate or severely reduce histamine levels in all cells through reducing Hdc transcript levels. Recently, we have characterized an Hdc transgene P[gHdc⁺;w⁺] in an Hdc null mutant background that rescues the Hdc mutant phenotype completely, restoring histamine in all cells and developmental stages. A set of deletions in the 5 noncoding region of the P[gHdc⁺;w⁺] transgene were made, some of which eliminate Hdc expression in adult central brain neurons. We are now using these gHdc transgene deletions to determine whether histamine deficiency in the central brain or peripheral tissues could disrupt a complex behavior, such as courtship. Virgin male and female flies were introduced into a small chamber to observe courtship behavior, and the time after introduction at which the various steps of courtship were exhibited was recorded. Results indicate that a total lack of histamine has a profound effect on the ability of flies to exhibit a normal courtship behavioral repertoire. Preliminary results also indicate that flies with only a CNS histamine deficiency appear to be disrupted in some aspects of courtship, although the precise effects are still being investigated.