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Tyrosine hydroxylase in vasopressinergic axons of the pituitary posterior lobe of rats under salt-loading as a manifestation of neurochemical plasticity.

Abstract：

:In this study, we attempted to test whether tyrosine hydroxylase (TH), the first rate-limiting enzyme of catecholamine synthesis, is confined to the perikarya of activated magnocellular vasopressinergic (VPergic) neurons or is also present in their distal axons in the pituitary posterior lobe (PL). In addition, we evaluated the possible correlation between TH and VP turnover in the axons of rats drinking 2% NaCl for 1, 2, and 3 weeks. To this aim, we examined the large swellings of VPergic axons, the so-called Herring bodies, using the double-immunofluorescent technique and the avidinbiotin technique, combined with image analysis. Here we have demonstrated for the first time a colocalization of TH and VP in Herring bodies, which is a strong argument in favor of TH transport from the perikarya of VPergic neurons via axons toward their terminals. TH-immunoreactive (IR) and VP-IR materials were distributed in Herring bodies with seeming zonality. The number of VP-IR Herring bodies decreased by a factor of four over the first week of osmotic stimulation, remaining at almost the same low level until the end of the experiment. Conversely, the content of the VP-IR material within the individual Herring bodies fell gradually during the three weeks of salt-loading. The results suggest that VP depletion from Herring bodies prevails in its transport into these structures during the whole period of osmotic stimulation. In contrast to VP-IR Herring bodies, the number of TH-IR Herring bodies and the content of TH-IR material within the individual Herring bodies increased progressively during the entire experiment. The synchronization of the VP depletion and TH accumulation in Herring bodies during long-term osmotic stimulation raised the question about a possible functional interaction between both substances.

journal_name

Neural Plast

journal_title

Neural plasticity

authors

Abramova M,Calas A,Thibault J,Ugrumov M

doi

10.1155/NP.2000.179

keywords:

subject

Has Abstract

pub_date

2000-01-01 00:00:00

pages

179-91

issue

eissn

2090-5904

issn

1687-5443

journal_volume

pub_type

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Tyrosine hydroxylase in vasopressinergic axons of the pituitary posterior lobe of rats under salt-loading as a manifestation of neurochemical plasticity.