title: Cellular and subcellular localization of alpha-1 adrenoceptors in the rat visual cortex.
abstract: Noradrenaline is thought to play modulatory roles in a number of physiological, behavioral, and cellular processes. Although many of these modulatory effects are mediated through alpha-1 adrenoceptors, basic knowledge of the cellular and subcellular distributions of these receptors is limited. We investigated the laminar distribution pattern of alpha-1 adrenoceptors in rat visual cortex, using immunohistochemistry at both light and electron microscopic levels. Affinity-purified anti-alpha-1 antibody was confirmed to react only with a single band of about 70-80 kDa in total proteins prepared from rat visual cortex. Alpha-1 adrenoceptors were widely distributed though all cortical layers, but relatively high in density in layers I, II/III, and V. Immunoreactivity was observed in both neuronal perikarya and processes including apical dendrites. In double-labeling experiments with anti-microtubule-associated protein 2, anti-neurofilament, anti-glial fibrillary acidic protein, anti-glutamic acid decarboxylase 65/67, anti-2-3-cyclic nucleotide 3-phosphodiesterase, and anti-tyrosine hydroxylase antibodies, alpha-1 adrenoceptors were found mainly in dendrites and somata of microtubule-associated protein 2-immunopositive neurons. About 20% of alpha-1 adrenoceptors were in GABAergic neurons. A small number of alpha-1 adrenoceptors were also distributed in axons of excitatory neurons, astrocytes, oligodendrocytes and noradrenergic fibers. Using an immunoelectron microscopic technique, numerous regions of alpha-1 adrenoceptor immunoreactivity were found in cell somata, on membranes of dendrites, and in postsynaptic regions. Moreover, a small number of immunoreaction products were also detected in axons and presynaptic sites. These findings provide the first quantitative evidence regarding the cellular and subcellular localization of alpha-1 adrenoceptor immunoreactivity in visual cortex. Moreover, the ultrastructural distribution of alpha-1 adrenoceptor immunoreactivity suggests that alpha-1 adrenoceptors are transported mainly into dendrites and that they exert effects at postsynaptic sites of neurons.
authors.affiliation: Department of Histology and Neurobiology, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu-machi, Tochigi 321-0293, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakadate
authors.forename: K
authors.initials: K
authors.lastname: Imamura
authors.forename: Y
authors.initials: Y
authors.lastname: Watanabe
mesh_terms: D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western / Q000379:methods; D003952:Diagnostic Imaging / Q000379:methods; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D016253:Microscopy, Immunoelectron / Q000379:methods; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure*; D051381:Rats; D020318:Rats, Long-Evans; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism / Q000648:ultrastructure; D014793:Visual Cortex / Q000166:cytology* / Q000378:metabolism*
chemical_list: C489787:MAP2 protein, rat; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D018340:Receptors, Adrenergic, alpha-1; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases