Effect of hypoosmolality on the abundance, poly(A) tail length and axonal targeting of arginine vasopressin and oxytocin mRNAs in rat hypothalamic magnocellular neurons

Abstract

Arginine vasopressin (AVP) and oxytocin (OT) mRNAs are targeted to the axonal compartment of rat hypothalamic magnocellular neurons. Salt-loading results in a considerable rise in hypothalamic and axonal AVP mRNA but only a moderate increase for axonal OT mRNA. Here we report that hypoosmolality gives rise to a rapid decrease of axonal AVP encoding transcripts to undetectable levels after 2 weeks. The levels of OT mRNA in the axonal compartment did not change significantly. In the hypothalamus the mRNA for AVP also decreased. The size of the poly(A) tract of AVP encoding transcripts appeared to be strictly correlated with plasma osmolality. In contrast, the amount and size of OT encoding mRNAs were only moderately or not influenced by hypoosmolar stimuli.infusion of the AVP V2-receptor agonist 1-deamino-[8-D-arginine] vasopressin (DDAVP) by use of subcutaneously implanted osmotic minipumps combined with a liquid diet to induce overhydration. In the hypothalamus hypoosmolality induced a reduction in both the abundance of AVP mRNA and the length of its poly(A) tract; the latter appears to be strictly correlated with plasma osmolality. In addition, a rapid and steady depletion of the axonal AVP mRNA pool was observed with undetectable levels after 2 weeks of overhydration. Surprisingly, the oxytocinergic system was considerably less affected by this treatment. Materials and methods

The Effect of Acute and Chronic Social Stress on the Hippocampal Transcriptome in Mice

“…AVP innervation to hippocampus originates mainly from the paraventricular nucleus of hypothalamus (PVN) [ 96 ] controlling the release of stress hormones. A possible source of increased level of Avp transcripts in the hippocampal tissue may be the axonal transport of mRNA from the PVN because Avp mRNA is up-regulated by stress in PVN [ 97 ] and is transported into axons [ 98 ]. Fabp7 gene encodes the brain fatty acid binding protein that regulates hippocampal functions such as neurogenesis and behavior [ 99 ] and may be associated with psychiatric disorders [ 100 , 101 ].…”

Endoplasmic reticulum stress in vasopressin neurons of familial diabetes insipidus model mice: aggregate formation and mRNA poly(A) tail shortening

“…The mRNA poly(A) tail length of some secreted or transmembrane proteins is reported to change in several conditions. This is also true for neurohypophysial hormones, as follows: osmotic stimulus induced elongation of AVP and OT mRNA poly(A) tails, accompanied by increases in the mRNA expression in the SON (Carrazana et al 1988; Zigg et al 1988; Carter & Murphy, 1991); hyponatraemia induced shortening of the AVP and OT mRNA poly(A) tail (Chooi et al 1992; Svane et al 1995); and the circadian peak of AVP mRNA expression in the suprachiasmatic nucleus was accompanied by elongation of the AVP mRNA poly(A) tail length (Robinson et al 1988). These data suggest that the length of the poly(A) tail is a crucial determinant of AVP and OT mRNA stability.…”

Selective Inhibition of Magnocellular Vasopressin Neurons by Hypoosmolality: Effect on Histamine- and Stress-Induced Secretion of Adrenocorticotropin and Prolactin

“…Furthermore, AVP synthesis in magnocellular neurons as indicated by AVP mRNA levels is virtually turned off after 7 days of DDAVP treatment [16]. In addition, it has recently been found that also the axonal content of AVP mRNA is reduced in parallel [10]. However, basal plasma levels of AVP remain unchanged in hypoosmolar rats [8].…”

“…The control group consisted of rats implanted with vehicle-loaded pumps and submitted to the same diet as the DDAVP-treated rats plus water ad libitum. The hypoosmolality protocol used by us has been thoroughly evaluated elsewhere [10] including demonstration of a continuous weight gain after surgery similar to that observed in control rats.…”