title: Neurotransmitters, receptors, and neuropeptides in the accessory optic system: an immunohistochemical survey in the pigeon (Columba livia).
abstract: Immunohistochemical techniques were used to survey the distribution of several conventional transmitters, receptors, and neuropeptides in the pigeon nucleus of the basal optic root (nBOR), a component of the accessory optic system. Amongst the conventional neurotransmitters/modulators, the most intense labeling of fibers/terminals within the nBOR was obtained with antisera directed against glutamic acid decarboxylase (GAD) and serotonin (5-HT). Moderately dense fiber plexuses were seen to label with antibodies directed against tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT). GAD-like immunoreactivity (GAD-LI) was found in many small and medium-sized perikarya within the nBOR. Some of the medium-sized cells were occasionally positive for ChAT-LI. Cell body and dendritic staining was also commonly seen with the two tested antisera against receptors-anti-GABA-A receptor and anti-nicotinic acetylcholine receptor. The antisera directed against various neuropeptides produced only fiber labeling within the nBOR. The densest fiber plexus staining was observed with antiserum against neuropeptide Y (NPY-LI), while intermediate fiber densities were seen for substance P (SP-LI) and cholecystokinin (CCK-LI). A few varicose fibers were labeled with antisera against neurotensin (NT), leucine-enkephalin (L-ENK), and the vasoactive intestinal polypeptide (VIP). Unilateral enucleation produced an almost complete elimination of TH-LI in the contralateral nBOR. SP-LI and CCK-LI were also decreased after enucleation. No apparent changes were seen for all other substances. These results indicate that a wide variety of chemically-specific systems arborize within the nBOR. Three of the immunohistochemically defined fiber systems (TH-LI, SP-LI, and CCK-LI fibers) were reduced after removal of the retina, which may indicate the presence of these substances in retinal ganglion cells. In contrast, the fibers exhibiting ChAT-LI, GAD-LI, 5-HT-LI, NPY-LI, NT-LI, L-ENK-LI, and VIP-LI appear to be of nonretinal origin. Two different populations of nBOR neurons exhibited GAD-LI and ChAT-LI. However, these two populations together constituted only about 20% of the nBOR neurons.
authors.affiliation: Department of Physiology and Biophysics, São Paulo State University (USP), Brazil.
authors.forename: L R
authors.initials: LR
authors.lastname: Britto
authors.forename: D E
authors.initials: DE
authors.lastname: Hamassaki
authors.forename: K T
authors.initials: KT
authors.lastname: Keyser
authors.forename: H J
authors.initials: HJ
authors.lastname: Karten
mesh_terms: D000818:Animals; D010856:Columbidae; D015353:Eye Enucleation; D005455:Fluorescent Antibody Technique; D007124:Immunoenzyme Techniques; D009479:Neuropeptides / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011950:Receptors, Cholinergic / Q000378:metabolism; D011963:Receptors, GABA-A / Q000378:metabolism; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000378:metabolism*; D014795:Visual Pathways / Q000166:cytology / Q000378:metabolism*
chemical_list: D009479:Neuropeptides; D018377:Neurotransmitter Agents; D011950:Receptors, Cholinergic; D011963:Receptors, GABA-A; D017981:Receptors, Neurotransmitter