Association of dopaminergic fibers with corticotropin releasing hormone (CRH)-synthesizing neurons in the paraventricular nucleus of the rat hypothalamus

Z. Liposits, W. K. Paull

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42 Citations (Scopus)

Abstract

Catecholamines are known to exert a central influence on the hypothalamo-hypophyseal-adrenal neuroendocrine system. The selective dopaminergic innervation of the hypothalamic paraventricular nucleus (PVN) and putative relationships between dopaminergic fibers and corticotropin releasing hormone (CRH)-synthesizing neurons were studied in the male rat by means of immunocytochemistry following the elimination of noradrenergic and adrenergic inputs to the hypothalamus. A 3.0-mm-wide coronal cut was placed unilaterally in the brain at the rostral level of the mesencephalon. All neuronal structures from the cortex to the ventral surface of the brainstem, including the ascending catecholaminergic fiber bundles were transected. This surgical intervention resulted in the accumulation of dopamine-β-hydroxylase (DBH)-immunoreactivity in axons proximal to the cut, and an almost complete disappearance of DBH activity in those located distal to the lesion. Two weeks following the operation, DBH immunoreactivity was significantly diminished in the PVN located on the side of lesion, while tyrosine hydroxylase (TH)-immunoreactivity was present in a substantial number of fibers in the same nucleus. Both DBH- and TH-immunoreactive axons were preserved in the contralateral PVN. Simultaneous immunocytochemical localization of either DBH- or TH-IR fibers and corticotropin releasing hormone-synthesizing neurons in the hypothalami from brainstem-lesioned, colchicine treated animals revealed that the distribution of catecholaminergic fibers and CRH neurons is homologous within the PVN of the intact side. Only a few scattered DBH-immunoreactive axons were detected among CRH-producing neurons in the PVN on the side of the lesion. In contrast, many tyrosine hydroxylase containing neurons and neuronal processes were observed on the lesioned side and the TH-IR fibers established juxtapositions with CRH-synthesizing neurons. These morphological data demonstrate that following the surgical ablation of noradrenergic and adrenergic afferents to the PVN, a substantial number of tyrosine hydroxylase-IR fibers remained in the nucleus and they were associated with corticotropin releasing hormone synthesizing neurons. Therefore, it is hypothesized that the paraventricular nucleus receives a selective dopaminergic innervation and these dopaminergic axons might influence the function of the pituitary and adrenal glands via the hypothalamic CRH system.

Original languageEnglish
Pages (from-to)119-127
Number of pages9
JournalHistochemistry
Volume93
Issue number2
DOIs
Publication statusPublished - Dec 1989

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Paraventricular Hypothalamic Nucleus
Corticotropin-Releasing Hormone
Tyrosine 3-Monooxygenase
Hypothalamus
Neurons
Axons
Adrenergic Agents
Brain Stem
Pituitary Hormone-Releasing Hormones
Neurosecretory Systems
Colchicine
Pituitary Gland
Adrenal Glands
Mesencephalon
Mixed Function Oxygenases
Catecholamines
Dopamine
Immunohistochemistry
Brain

ASJC Scopus subject areas

  • Anatomy

Cite this

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title = "Association of dopaminergic fibers with corticotropin releasing hormone (CRH)-synthesizing neurons in the paraventricular nucleus of the rat hypothalamus",
abstract = "Catecholamines are known to exert a central influence on the hypothalamo-hypophyseal-adrenal neuroendocrine system. The selective dopaminergic innervation of the hypothalamic paraventricular nucleus (PVN) and putative relationships between dopaminergic fibers and corticotropin releasing hormone (CRH)-synthesizing neurons were studied in the male rat by means of immunocytochemistry following the elimination of noradrenergic and adrenergic inputs to the hypothalamus. A 3.0-mm-wide coronal cut was placed unilaterally in the brain at the rostral level of the mesencephalon. All neuronal structures from the cortex to the ventral surface of the brainstem, including the ascending catecholaminergic fiber bundles were transected. This surgical intervention resulted in the accumulation of dopamine-β-hydroxylase (DBH)-immunoreactivity in axons proximal to the cut, and an almost complete disappearance of DBH activity in those located distal to the lesion. Two weeks following the operation, DBH immunoreactivity was significantly diminished in the PVN located on the side of lesion, while tyrosine hydroxylase (TH)-immunoreactivity was present in a substantial number of fibers in the same nucleus. Both DBH- and TH-immunoreactive axons were preserved in the contralateral PVN. Simultaneous immunocytochemical localization of either DBH- or TH-IR fibers and corticotropin releasing hormone-synthesizing neurons in the hypothalami from brainstem-lesioned, colchicine treated animals revealed that the distribution of catecholaminergic fibers and CRH neurons is homologous within the PVN of the intact side. Only a few scattered DBH-immunoreactive axons were detected among CRH-producing neurons in the PVN on the side of the lesion. In contrast, many tyrosine hydroxylase containing neurons and neuronal processes were observed on the lesioned side and the TH-IR fibers established juxtapositions with CRH-synthesizing neurons. These morphological data demonstrate that following the surgical ablation of noradrenergic and adrenergic afferents to the PVN, a substantial number of tyrosine hydroxylase-IR fibers remained in the nucleus and they were associated with corticotropin releasing hormone synthesizing neurons. Therefore, it is hypothesized that the paraventricular nucleus receives a selective dopaminergic innervation and these dopaminergic axons might influence the function of the pituitary and adrenal glands via the hypothalamic CRH system.",
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N2 - Catecholamines are known to exert a central influence on the hypothalamo-hypophyseal-adrenal neuroendocrine system. The selective dopaminergic innervation of the hypothalamic paraventricular nucleus (PVN) and putative relationships between dopaminergic fibers and corticotropin releasing hormone (CRH)-synthesizing neurons were studied in the male rat by means of immunocytochemistry following the elimination of noradrenergic and adrenergic inputs to the hypothalamus. A 3.0-mm-wide coronal cut was placed unilaterally in the brain at the rostral level of the mesencephalon. All neuronal structures from the cortex to the ventral surface of the brainstem, including the ascending catecholaminergic fiber bundles were transected. This surgical intervention resulted in the accumulation of dopamine-β-hydroxylase (DBH)-immunoreactivity in axons proximal to the cut, and an almost complete disappearance of DBH activity in those located distal to the lesion. Two weeks following the operation, DBH immunoreactivity was significantly diminished in the PVN located on the side of lesion, while tyrosine hydroxylase (TH)-immunoreactivity was present in a substantial number of fibers in the same nucleus. Both DBH- and TH-immunoreactive axons were preserved in the contralateral PVN. Simultaneous immunocytochemical localization of either DBH- or TH-IR fibers and corticotropin releasing hormone-synthesizing neurons in the hypothalami from brainstem-lesioned, colchicine treated animals revealed that the distribution of catecholaminergic fibers and CRH neurons is homologous within the PVN of the intact side. Only a few scattered DBH-immunoreactive axons were detected among CRH-producing neurons in the PVN on the side of the lesion. In contrast, many tyrosine hydroxylase containing neurons and neuronal processes were observed on the lesioned side and the TH-IR fibers established juxtapositions with CRH-synthesizing neurons. These morphological data demonstrate that following the surgical ablation of noradrenergic and adrenergic afferents to the PVN, a substantial number of tyrosine hydroxylase-IR fibers remained in the nucleus and they were associated with corticotropin releasing hormone synthesizing neurons. Therefore, it is hypothesized that the paraventricular nucleus receives a selective dopaminergic innervation and these dopaminergic axons might influence the function of the pituitary and adrenal glands via the hypothalamic CRH system.

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