The determination of histamine in the Drosophila head

Histamine is a neurotransmitter at arthropod photoreceptors. Even though th e fruit fly, Drosophila melanogaster, is a widely used model in neuroscienc e research, the histamine content of its nervous system has not so far been reported. We have developed a high performance liquid chromatography (HPLC ) method with pre-column o-phtaldialdehyde-mercaptoethanol (OPA-ME) derivat ization and electrochemical detection, to determine this amine in Drosophil a. The histamine content of the fly's head averages about 2.0 ng per head. In heads of the mutant hdc(JK910), a presumed null for the gene encoding th e enzyme that synthesizes histamine, histamine was not detected in measurab le amounts. In heads of the mutant sine oculis, which lacks compound eyes, only 28% of this amine was found compared with wild type flies, so histamin e is mainly present in the compound eye photoreceptors. Also observed in hi stamine-deficient mutants was a decrease in the peak which contains a subst ance having the same retention time as carcinine (beta -alanyl-histamine). Our method was not able to detect compounds previously reported as histamin e metabolites in insects. In spite of this, the method we have developed en ables the fast and accurate measurement of histamine in the heads of Drosop hila, suitable for screening mutants. (C) 2000 Elsevier Science B.V. All ri ghts reserved.