Histamine-like immunoreactivity in the visual system and brain of Drosophila melanogaster

In this study, immunohistochemistry on cryostat sections is used to demonstrate anti-histamine immunoreactivity in the Drosophila brain. The results support earlier findings that histamine is probably a transmitter of insect photoreceptors. It is further shown that, in Drosophila, all imaginal photoreceptors including receptor type R7 are anti-histamine immunoreactive, whereas the larval photoreceptors do not seem to contain histamine. In addition to the photoreceptors, fibres in the antennal nerve and approximately 12 neurons in each brain hemisphere show strong histamine-like immunoreactivity. These cells arborize extensively in large parts of the central brain.