ISSN:
1432-0878
Keywords:
Key words: Suprachiasmatic nucleus
;
Catecholamines
;
Dopamine
;
Electron microscopy
;
Vasoactive intestinal peptide
;
Vasopressin
;
Rat (Sprague Dawley)
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract. Catecholaminergic fibers in the suprachiasmatic nucleus of adult rats were investigated by use of light- and electron-microscopic immunocytochemistry. The suprachiasmatic nucleus receives a modest density of tyrosine hydroxylase-containing axons, homogeneously distributed in the nucleus and forming varicosities throughout its entire rostro-caudal extension. Immunolabeling with antibodies against dopamine showed that this catecholamine input comprises a dopaminergic component. Many tyrosine hydroxylase-positive cells were localized at the immediate periphery of the suprachiasmatic nucleus. With electron-microscopic examination, dendrites of these neurons were found within the limits of the nucleus as well as at a border zone between the suprachiasmatic nucleus proper and the optic tract where they received unlabeled synapses, providing a morphological support for a possible role of dopaminergic neurons in the integration and/or transfer of light-related signals. More than 91% of catecholaminergic axonal varicosities were found to establish morphologically defined synapses with dendrites. To investigate whether these synapses might be shared with neurons of one or both of the two main peptidergic populations of the nucleus, namely vasoactive intestinal peptide- and vasopressin-containing neurons, we carried out double-labeling experiments combining immunoperoxidase and immunogold-silver labeling. Results showed only a few cases of direct association of the catecholaminergic termin als with these peptidergic categories. In both types of dually stained sections, catecholaminergic synapses were preferentially made with unlabeled dendrites. The homogeneous distribution of tyrosine hydroxylase-immunoreactive fibers in the suprachiasmatic nucleus could therefore reflect a lack of significant catecholaminergic innervation of both vasoactive intestinal peptide- and vasopressin-synthesizing neurons.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00304514
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