Elsevier

Brain Research

Volume 650, Issue 2, 11 July 1994, Pages 181-204
Brain Research

Research report
Perikaryal and synaptic localization ofα2A-adrenergic receptor-like immunoreactivity

https://doi.org/10.1016/0006-8993(94)91782-5Get rights and content

Abstract

Through molecular cloning, the existence of three distinct subtypes ofα2-adrenergic receptors (α2AR) - A, B and C - has been established and are referred to asα2AAR, α2BAR andα2CAR. Due to limitations in pharmacological tools, it has been difficult to ascribe the role of each subtype to the central functions ofα2AR. In situ hybridization studies have provided valuable information regarding their distribution within brain. However, little is known about their subcellular distribution, and in particular, their pre- versus postsynaptic localization or their relation to noradrenergic neurons in the CNS. We used an antiserum that selectively recognizes the A-subtype ofα2AR to determine: (1) the regional distribution of the receptor within brains of rat and monkey; (2) the subcellular distribution of the receptor in locus coeruleus (LC) of rats and prefrontal cortex of monkeys; and (3) the ultrastructural relation of the receptor to noradrenergic processes in LC. Light microscopic immunocytochemistry revealed prominent immunoreactivity in LC, the brainstem regions modulating the baroreflex, the granule cell layer of the cerebellar cortex, the paraventricular and supraoptic nuclei of the hypothalamus (PVN, SON), the basal ganglia, all thalamic nuclei, the hippocampal formation and throughout cerebral cortical areas. Comparison of results obtained from rat and monkey brains revealed no apparent interspecies-differences in the regional distribution of immunoreactivity. Immunoreactivity occurred as small puncta, less than 1 μm in diameter, that cluster over neuronal perikarya. Besides these puncta, cell bodies, proximal dendrites and fine varicose processes - most likely to be axonal - of the PVN and SON and the hippocampal granule cells also exhibited homogeneously intense distribution of immunoreactivity. Subcellularly,α2AAR-ir in LC and prefrontal cortex were associated with synaptic and non-synaptic plasma membrane of dendrites and perikarya as well as perikaryal membranous organelles. In addition, cortical tissue, but not LC, exhibited prominent immunoreactivity within spine heads. Rat brainstem tissue immunolabeled dually forα2AAR and dopamine β-hydroxylase (DβH, the noradrenaline-synthesizing enzyme) revealed thatα2AAR-li occurs in catecholaminergic terminals but is also prevalent within non-catecholaminergic terminals. Terminals exhibitingα2AAR-li formed symmetric and asymmetric types of synapses onto dendrites with and without DβH-immunoreactivity. These results indicate that: (1) the A-subtype ofα2AR is distributed widely within brain; (2)α2AAR-li reflects the presence of newly synthesizedα2AAR in perikarya as well as those receptors along the plasma membrane of perikarya, dendritic trunks and spines; and (3)α2AAR in LC may operate as heteroreceptors on non-catecholaminergic terminals as well as autoreceptors on noradrenergic terminals.

References (79)

  • HarleyC.

    Noradrenergic and locus coeruleus modulation of the perforant path-evoked potential in rat dentate gyrus supports a role for the locus coeruleus in attentional memorial processes

    Prog. Brain Res.

    (1991)
  • HarrisonJ.K. et al.

    Molecular characterization of α1- and α2-adrenoceptors

    Trends Pharmacol.

    (1991)
  • HerkenhamM.

    Mismatches between neurotransmitter and receptor localization in brain: observations and implications

    Neuroscience

    (1987)
  • JonesB.E.

    Noradrenergic locus coeruleus neurons: their distant connections and their relationship to neighboring (including cholinergic and GABAergic) neurons of the central gray and reticular formation

    Prog. Brain Res.

    (1991)
  • JonesC.R. et al.

    Autoradiography of adrenoceptors in rat and human brain: α-adrenoceptor and idazoxan binding sites

    Prog. Brain Res.

    (1991)
  • McCabeJ.T. et al.

    Clonidine-induced feeding: analysis of central sites of action and fiber projections mediating this response

    Brain Res.

    (1984)
  • McCormickD.A. et al.

    Actions of norepinephrine in the cerebral cortex and thalamus: implications for function of the central noradrenergic system

    Prog. Brain Res.

    (1991)
  • MeeleyM.P. et al.

    An endogenous clonidine-displacing substance from bovine brain: receptor binding and hypotensive actions in the ventrolateral medulla

    Life Sci.

    (1986)
  • MesulamM.M. et al.

    Atlas of cholinergic neurons in the forebrain and upper brainstem of the macaque based on monoclonal choline acetyltransferase histochemistry

    Neuroscience

    (1984)
  • MilnerT.A. et al.

    Ultrastructural localization of phenylethanolamineN-methyltransferase-like immunoreactivity in the rat locus coeruleus

    Brain Res.

    (1989)
  • PariniA. et al.

    Characterisation of an imidazoline/guanidinium receptive site distinct from the α2-adrenergic receptor

    J. Biol. Chem.

    (1989)
  • Pera¨la¨M. et al.

    Differential expression of two α2-adrenergic receptor subtype mRNAs in human tissues

    Mol. Brain Res.

    (1992)
  • PieriboneV.A. et al.

    Adrenergic and non-adrenergic neurons of the C1 and C2 areas project to locus coeruleus: a fluorescent double labeling study

    Neurosci. Lett.

    (1988)
  • RuggieroD.A. et al.

    Central control of the circulation by the rostral ventrolateral reticular nucleus: anatomical substrates

    Prog. Brain Res.

    (1989)
  • SakaiK. et al.

    Afferent projections to the cat locus coeruleus as visualized by the horseradish peroxidase technique

    Brain Res.

    (1977)
  • SalmA.K. et al.

    The evidence for astrocytes as a target for central noradrenergic activity: expression of adrenergic receptors

    Brain Res. Bull.

    (1992)
  • SawchenkoP.E. et al.

    The organization of noradrenergic pathways from the brainstem to the paraventricular and supraoptic nuclei in the rat

    Brain Res. Rev.

    (1982)
  • SegalM. et al.

    Actions of norepinephrine in the rat hippocampus

    Prog. Brain Res.

    (1991)
  • UnnerstallJ.R. et al.

    Distribution of α2-agonist binding sites in the rat and human central nervous system: analysis of some functional, anatomic correlates of the pharmacologic effects of clonidine and related adrenergic agents

    Brain Res. Rev.

    (1984)
  • WilliamsJ.T. et al.

    Synaptic potentials in locus coeruleus neurons in brain slices

    Prog. Brain Res.

    (1991)
  • ZonnenscheinR. et al.

    Imidazoline receptors in rat liver cells: a novel receptor or a subtype of α2-adrenergic receptors?

    Eur. J. Pharmacol.

    (1990)
  • AokiC.

    β-Adrenergic receptors: astrocytic localization in the adult visual cortex and their relation to catecholamine axon terminals as revealed by electron microscopic immunocytochemistry

    J. Neurosci.

    (1992)
  • AokiC. et al.

    Cholinergic terminals in the cat visual cortex: ultrastructural basis for interaction with glutamate-immunoreactive neurons and other cells

    Vis. Neurosci.

    (1992)
  • ArnstenA.F.R. et al.

    α2-Adrenergic mechanisms in prefrontal cortex associated with cognitive decline in aged nonhuman primates

    Science

    (1985)
  • BerodA. et al.

    Catecholaminergic and GABAergic anatomical relationship in the rat substantia nigra, locus coeruleus and hypothalamic median eminence: Immunocytochemical visualization of biosynthetic enzymes on serial semithin plastic-embedded sections

    J. Histochem. Cytochem.

    (1984)
  • Bjo¨rklundA. et al.

    Catecholaminergic brainstem regulatory system

  • BoyajianC.L. et al.

    Anatomical evidence for alpha-2 adrenoceptor heterogeneity: differential autoradiographic distribution of [3H]rauwolscine and [3H]idazoxan in rat brain

    J. Pharmacol. Exp. Ther.

    (1987)
  • BylundD.B.

    Subtype of α1- and α2-adrenergic receptors

    FASEB J.

    (1992)
  • CederbaumJ.M. et al.

    Afferent projections to the rat locus coeruleus as determined by a retrograde tracing technique

    J. Comp. Neurol.

    (1978)
  • Cited by (188)

    • The Locus Coeruleus – Noradrenaline system: Looking into Alzheimer's therapeutics with rose coloured glasses

      2022, Biomedicine and Pharmacotherapy
      Citation Excerpt :

      The circulation as well as affinity of the adrenergic receptors vary greatly. For instance, the prefrontal cortex mainly comprises of α2 adrenergic receptors, due to which NA in this region exhibits elevated proximity towards α2 adrenoreceptors as well as alleviated proximity towards α1 and β adrenoreceptors [119,120]. Under the conditions of arousal, the noradrenergic processes (specifically beta adrenoreceptors) are associated with elevated selectivity.

    View all citing articles on Scopus
    **

    Present address: University of Tokyo, Dept. Toxicology and Pharmacology, Faculty of Pharmaceutical Sciences, Hongo 7-3-1, Bunkyoku, Tokyo 113, Japan.

    View full text