Histamine: a neurotransmitter candidate for Drosophila photoreceptors.
Recent experimental evidence suggests that histamine might be the synaptic transmitter used by invertebrate photoreceptors. In the present study, we have examined whether histamine is a transmitter candidate for Drosophila photoreceptors. Our findings are as follows: (a) Large amounts of histamine are synthesized by wild-type heads, whereas heads from the eye-deficient mutants, eyes absent and sine oculis, show reduced histamine synthesis. (b) Histidine decarboxylase activity is approximately 10-fold higher in extracts of normal heads compared with that in the mutants. (c) Histamine taken up by fly heads is metabolized into N-acetylhistamine and imidazole-4-acetic acid. (d) Immunostaining of normal and sevenless heads with histamine-specific antisera demonstrates that histamine is present in photoreceptors R1-6 and R8. (e) Histamine synthesized from exogenously supplied [3H]histidine can be released by depolarization with 50 mM K+, and the release is Ca2+ dependent. These observations strongly suggest that histamine is a major neurotransmitter used by Drosophila photoreceptors.
Sarthy
P V
PV
Department of Ophthalmology, Northwestern University Medical School, Chicago, IL 60611.
D000818:Animals; D001692:Biological Transport; D004296:Dopa Decarboxylase / Q000378:metabolism; D004331:Drosophila melanogaster / Q000502:physiology*; D006632:Histamine / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D006636:Histamine Release; D006640:Histidine Decarboxylase / Q000378:metabolism; D007700:Kinetics; D009420:Nervous System / Q000378:metabolism; D009424:Nervous System Physiological Phenomena; D018377:Neurotransmitter Agents / Q000502:physiology*; D010786:Photoreceptor Cells / Q000502:physiology*
D018377:Neurotransmitter Agents; D006632:Histamine; D004296:Dopa Decarboxylase; D006640:Histidine Decarboxylase