Arginine Vasopressin mRNA Levels Research Articles

Differential hypothalamic arginine vasopressin response to glucocorticoid receptor antagonism in lean and obese Zucker rats.

The obese Zucker rat (fa/fa) is an animal model for genetic obesity characterized by hyperphagia, hyperinsulinemia, and severe insulin resistance in peripheral tissues. Adrenal steroids seem to play an important role in the onset of fatty syndrome in these animals. There is strong evidence of abnormal regulation of the hypothalamic-pituitary-adrenal axis in obese Zucker rats. Considering the physiological function of arginine vasopressin (AVP) as an adrenocorticotropic hormone secretagogue, the present study was carried out to investigate the role of glucocorticoids in the control of hypothalamic AVP systems in lean and obese Zucker rats. In the first experiment, mifepristone (RU 38486), a glucocorticoid receptor antagonist, was administered for 4 days (10 mg/kg orally twice daily), and the expression of AVP mRNA in hypothalamic paraventricular and supraoptic nuclei was measured using in situ hybridization, and the concentrations of AVP in the pituitary gland and in the median eminence were quantified. Plasma corticosterone levels were also analyzed. Mifepristone treatment resulted in a threefold increase in plasma corticosterone levels in lean Zucker rats, but it did not change corticosterone secretion in obese animals. Mifepristone treatment decreased AVP mRNA levels in lean animals in the supraoptic nuclei, while in obese animals the AVP mRNA content was increased in the paraventricular nuclei. Mifepristone treatment significantly increased the concentration of AVP in the median eminence in lean rats and decreased it in obese animals. Mifepristone treatment did not change concentrations of AVP in the pituitary gland. In the second experiment, mifepristone was given for 4 days (10 mg/kg orally twice daily), and its effects on 24-hour food intake and plasma AVP concentrations were measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Food deprivation decreases vasopressin mRNA in the supraoptic and paraventricular nuclei of the hypothalamus in rats.

We examined the effect of food deprivation for three days on hypothalamic arginine vasopressin (AVP) mRNA in rats. Simultaneously the effect of water deprivation for the same period was examined as a model of dehydration. Levels of AVP mRNA in the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) were determined by semiquantitative in situ hybridization histochemistry. Water deprivation increased AVP mRNA in both nuclei as previously reported. In contrast, food deprivation decreased AVP mRNA in these nuclei. The changes in AVP mRNA levels in the PVN were observed in the magnocellular subdivision of the nucleus. Plasma levels of ACTH and corticosterone were greatly increased in both treated groups of rats. Plasma AVP and osmolality levels were significantly elevated in water-deprived rats but not in food-deprived rats. These observations indicated that both food deprivation and water deprivation stimulated the pituitary-adrenal axis and that a reduction in AVP mRNA levels in food-deprived rats was caused by food deprivation but not by glucocorticoid feedback suppression nor by altered plasma osmolality.

Genomic Effects of Cold and Isolation Stress on Magnocellular Vasopressin mRNA‐Containing Cells in the Hypothalamus of the Rat

We assessed the effects of cold and isolation stress on arginine vasopressin (AVP) mRNA in the paraventricular (PVN) and supraoptic (SON) nuclei of the hypothalamus. Vasopressin mRNA levels were determined by in situ hybridization histochemistry at the cellular level. In posterior magnocellular neurons of the PVN isolation stress for 7 or 14 days increased vasopressin mRNA levels 28 and 29%, respectively, compared to group-housed controls. No significant alterations in vasopressin gene expression were observed in the SON after 7 or 14 days of isolation stress. Scattered magnocellular AVP mRNA-expressing cells of the medial parvocellular PVN showed increases of 19 and 34% after 7 and 14 days of isolation, respectively. We also studied the effect of cold or combined cold and isolation stress on vasopressin gene expression in the PVN and SON. Cold stress for 3 h daily for 4 consecutive days increased AVP mRNA levels in the posterior magnocellular PVN by 15%. Cold-isolated animals showed an increase of 21%. No significant effect on AVP mRNA levels in the SON was observed. In contrast to the posterior magnocellular PVN, cold or cold-isolation stress increased AVP mRNA in magnocellular neurons of the medial parvocellular region of the PVN by 25 and 43%, respectively, relative to control rats. These results suggest that psychological and metabolic stress may be added to the list of stressors that activate the hypothalamo-neurohypophysial system.

Effects of hyperosmotic stimulation and adrenalectomy on vasopressin mRNA levels in the paraventricular and supraoptic nuclei of the hypothalamus: in situ hybridization histochemical analysis using a synthetic oligonucleotide probe.

The effects of salt loading and adrenalectomy on arginine vasopressin (AVP) mRNA levels in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) of the hypothalamus were studied by semiquantitative in situ hybridization histochemistry, using a synthetic oligonucleotide probe and a computer-assisted image analysis system. Salt loading (2% NaCl) for 7 days produced marked increases in AVP mRNA levels in the magnocellular neurons of the PVN, SON, and accessory nuclei. Adrenalectomy caused an increase in AVP mRNA expression in the magnocellular part of the PVN and the expansion of hybridization signals into its medial parvocellular region, where the cell bodies of corticotropin-releasing hormone (CRH) neurons are located. No apparent alteration of AVP mRNA levels was observed in the SON following adrenalectomy. These results indicate that hyperosmotic stimulation and the loss of circulating glucocorticoids had differential effects on AVP gene expression in the PVN and SON, and that the magnocellular PVN and SON neurons responded in different manners to the loss of feedback signals.

Developmental expression of corticotropin releasing hormone messenger RNA and peptide in rat hypothalamus

We have examined corticotropin releasing hormone (CRH), arginine vasopressin (AVP) and somatostatin (SOM) mRNA expression and peptide content in the rat hypothalamus from day 20 of fetal life (F20) to the fifteenth day of postnatal life (P15). During this time, hypothalamic CRH mRNA levels did not change significantly, whereas there was a gradual six-fold rise in CRH peptide levels. AVP mRNA levels fell three-fold between F20 and P1 and increased six-fold between P1 and P15. AVP peptide levels increased three-fold, with most of the rise occurring between P1 and P15. From F20 to P15, SOM mRNA and peptide levels rose four- and eight-fold, respectively. The changes in the levels of these three hypothalamic gene products correlate with the previously described alterations in the responsiveness of the HPA axis observed in fetal and early postnatal rats, suggesting a role for these neuropeptides in the modulation of the HPA axis during this developmental period.

Independent Regulation of Neuropeptide mRNA Level and Poly(A) Tail Length

Osmotic stimulation increases arginine-vasopressin (AVP) and oxytocin (OT) mRNA levels and poly(A) tail size concurrently. We now show that these changes are independently regulated. Whereas depletion of serotonin with p-chlorophenylalanine (PCPA) blocked the increase in hypothalamic levels of AVP and OT mRNA following osmotic stimuli in rats (2% saline drinking or dehydration), the increase in mRNA size was similar in PCPA and control animals. PCPA alone did not modify mRNA size. In addition to demonstrating an apparent obligatory role for serotonin in osmotically induced AVP and OT mRNA accumulation, the results provide evidence for different signaling pathways mediating transcript abundance and poly(A) tail length. Direct investigation of the regulatory mechanisms should be amenable to study in this system.