title: Immunocytochemical evidence for the presence of histamine and GABA in photoreceptors of the barnacle (Balanus nubilus).
abstract: Biochemical evidence indicates that GABA and histamine may both be synthesized by barnacle photoreceptors (Koike & Tsuda, 1980; Timpe & Stuart, 1984; Callaway & Stuart, 1989b). We used antisera against GABA- and histamine-protein conjugates to determine whether the photoreceptors contain either or both of these antigens. Both antisera labeled all of the photoreceptors in each of the three ocelli. Histamine-like immunoreactivity was found throughout each photoreceptor cell but was most intense at their presynaptic terminals. Histamine-like immunoreactivity was blocked by preincubation of the antibody either with histamine or with a histamine-protein conjugate. GABA-like immunoreactivity was found in all parts of the photoreceptors including the cell body, axon, rhabdomeric dendrites, and presynaptic terminals. GABA-protein conjugates blocked the GABA-like labeling of the photoreceptors, while protein conjugates with histamine, L-glutamate, L-glutamine, beta-alanine, and taurine did not. Histamine-like immunoreactivity in the supraesophageal ganglion was confined to the photoreceptor terminals and a second, loose plexus of endings in the main neuropil. GABA-like immunoreactivity, in contrast, was found in approximately twenty-five pairs of neurons of this ganglion. In the cirral nerves, which are expected to contain inhibitory motoneurons, unidentified axons also labeled with the GABA antiserum.
authors.affiliation: Department of Zoology, University of Washington, Seattle.
authors.forename: J C
authors.initials: JC
authors.lastname: Callaway
authors.forename: A E
authors.initials: AE
authors.lastname: Stuart
authors.forename: J S
authors.initials: JS
authors.lastname: Edwards
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D003429:Cross Reactions; D005724:Ganglia / Q000737:chemistry; D006632:Histamine / Q000032:analysis*; D007124:Immunoenzyme Techniques; D009474:Neurons / Q000737:chemistry; D010786:Photoreceptor Cells / Q000737:chemistry*; D001468:Thoracica; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
chemical_list: D005680:gamma-Aminobutyric Acid; D006632:Histamine