Histamine is known to be the neurotransmitter of insect photoreceptors. Histamine-like immunoreactivity is also found in a number of interneurons in the central nervous system of various insects. Here, we demonstrate by immunohistochemical techniques that, inDrosophila melanogaster(Acalypterae), most or all mechanosensory neurons of imaginal hair sensilla selectively bind antibodies directed against histamine. The histamine-like staining includes the cell bodies of these neurons as well as their axons, which form prominent fibre bundles in peripheral nerves, and their terminal projections in the central neuropil of head and thoracic ganglia. The specificity of the immunostaining is demonstrated by investigating aDrosophilamutant unable to synthesize histamine. Other mechanosensory organs, such as campaniform sensilla or scolopidial organs, do not stain. In the calypteran flies,MuscaandCalliphora, we find no comparable immunoreactivity associated with either hair sensilla or the nerves entering the central nervous system, observations in agreement with earlier studies onCalliphora. Thus, histamine seems to be a major mechanosensory transmitter candidate of the adult nervous system ofDrosophila, but apparently not ofMuscaorCalliphora.
展开▼
