scholarly journals Dehydration followed by sham rehydration contributes to reduced neuronal activation in vasopressinergic supraoptic neurons after water deprivation

2010 â—½  
Vol 299 (5) â—½  
pp. R1232-R1240 â—½  
Author(s):  
W. David Knight â—½  
Lisa L. Ji â—½  
Joel T. Little â—½  
J. Thomas Cunningham
Keyword(s):  
Supraoptic Nucleus â—½  
Water Deprivation â—½  
Isotonic Saline â—½  
Plasma Osmolality â—½  
Inhibitory Interneurons â—½  
Lamina Terminalis â—½  
Fos Expression â—½  
Supraoptic Neurons â—½  
Hypothalamic Activation

This experiment tested the role of oropharyngeal and gastric afferents on hypothalamic activation in dehydrated rats instrumented with gastric fistulas and allowed to drink water or isotonic saline compared with euhydrated controls (CON). Rats were water-deprived for 48 h (48 WD) or 46 h WD with 2 h rehydration with water (46+W) or isotonic saline (46+S). 46+W and 46+S rats were given water with fistulas open (46+WO/46+SO, sham) or closed (46+WC/46+SC). Compared with CON, water deprivation increased and water rehydration decreased plasma osmolality, while sham rehydration had no effect. Water deprivation increased c-Fos staining in the lamina terminalis. However, none of the sham or rehydration treatments normalized c-Fos staining in the lamina terminalis. Analysis of AVP and c-Fos-positive neurons in the supraoptic nucleus (SON) revealed reduced colocalization in 46+WO and 46+SC rats compared with 48 WD and 46+SO rats. However, 46+WO and 46+SC rats had higher c-Fos staining in the SON than 46+WC or CON rats. Examination of c-Fos in the perinuclear zone (PNZ) revealed that sham and rehydrated rats had increased c-Fos staining to CON, while 48 WD and 46+SO rats had little or no c-Fos staining in this region. Thus, preabsorptive reflexes contribute to the regulation of AVP neurons in a manner independent of c-Fos expression in the lamina terminalis. Further, this reflex pathway may include inhibitory interneurons in the PNZ region surrounding the SON.

Effects of water deprivation and rehydration on c-Fos and FosB staining in the rat supraoptic nucleus and lamina terminalis region

2005 â—½  
Vol 288 (1) â—½  
pp. R311-R321 â—½  
Author(s):  
Lisa L. Ji â—½  
Tiffany Fleming â—½  
Maurice L. Penny â—½  
Glenn M. Toney â—½  
J. Thomas Cunningham
Keyword(s):  
Plasma Proteins â—½  
Supraoptic Nucleus â—½  
Water Deprivation â—½  
Plasma Osmolality â—½  
Male Rats â—½  
Lamina Terminalis â—½  
Dependent Manner â—½  
Preoptic Nucleus â—½  
Plasma Measurements â—½  
Control Water

We studied cFos and FosB staining in the supraoptic nucleus (SON) the organum vasculosum of the lamina terminalis (OVLT) and the median preoptic nucleus (MnPO) in adult male rats after water deprivation (24 h, n = 11; 48 h, n = 12) and water deprivation with rehydration (22 h + water, n = 11; 46 h + water, n = 10). Control rats ( n = 15) had water available ad libitum. Separate sets of serial sections from each brain were processed for immunocytochemistry using primary antibodies against either c-Fos or FosB protein. Plasma osmolality, vasopressin, hematocrit, and plasma proteins were measured in separate groups ( n = 6–7). The number of c-Fos-positive cells in the SON was significantly increased after 24 and 48 h of water deprivation. In contrast, rehydrated groups were not different from control. Water deprivation significantly increased c-Fos staining in both the OVLT and the MnPO, but c-Fos staining was not altered by rehydration. FosB staining in the SON was significantly increased only by 48-h water deprivation, and this effect was significantly decreased by rehydration. In the MnPO and OVLT, FosB staining was significantly increased by water deprivation, and, like c-Fos staining, these increases were not affected by rehydration. Water deprivation significantly increased osmolality and hematocrit, as well as plasma protein and vasopressin concentrations. Plasma measurements from rehydrated rats were not different from control. We conclude that water deprivation and rehydration differentially affect c-Fos and FosB staining in a region-dependent manner.

scholarly journals Water deprivation-induced sodium appetite: humoral and cardiovascular mediators and immediate early genes

2002 â—½  
Vol 282 (2) â—½  
pp. R552-R559 â—½  
Author(s):  
Laurival A. De Luca â—½  
Zhice Xu â—½  
Guus H. M. Schoorlemmer â—½  
Robert L. Thunhorst â—½  
Terry G. Beltz â—½  
...  
Keyword(s):  
Water Deprivation â—½  
Plasma Osmolality â—½  
Plasma Renin â—½  
Preoptic Nucleus â—½  
Adult Rats â—½  
Sodium Appetite â—½  
Arterial Blood â—½  
Fos Expression â—½  
Total Body â—½  
Operational Criteria

10.1152/ajpregu.00295.2000. Adult rats deprived of water for 24–30 h were allowed to rehydrate by ingesting only water for 1–2 h. Rats were then given access to both water and 1.8% NaCl. This procedure induced a sodium appetite defined by the operational criteria of a significant increase in 1.8% NaCl intake (3.8 ± 0.8 ml/2 h; n = 6). Expression of Fos (as assessed by immunohistochemistry) was increased in the organum vasculosum of the lamina terminalis (OVLT), median preoptic nucleus (MnPO), subfornical organ (SFO), and supraoptic nucleus (SON) after water deprivation. After rehydration with water but before consumption of 1.8% NaCl, Fos expression in the SON disappeared and was partially reduced in the OVLT and MnPO. However, Fos expression did not change in the SFO. Water deprivation also 1) increased plasma renin activity (PRA), osmolality, and plasma Na+; 2) decreased blood volume; and 3) reduced total body Na+; but 4) did not alter arterial blood pressure. Rehydration with water alone caused only plasma osmolality and plasma Na+concentration to revert to euhydrated levels. The changes in Fos expression and PRA are consistent with a proposed role for ANG II in the control of the sodium appetite produced by water deprivation followed by rehydration with only water.

Drinking-induced thermoregulatory panting in rehydrated sheep: influences of oropharyngeal/esophageal signals, core temperature, and thirst satiety

2009 â—½  
Vol 296 (6) â—½  
pp. R1881-R1888 â—½  
Author(s):  
M. J. McKinley â—½  
F. Weissenborn â—½  
M. L. Mathai
Keyword(s):  
Drinking Water â—½  
Body Temperature â—½  
Core Temperature â—½  
Heat Load â—½  
Water Deprivation â—½  
Saline Solution â—½  
Isotonic Saline â—½  
Cool Water â—½  
Rapid Fall

Dehydrated mammals conserve body water by reducing thermoregulatory evaporative cooling responses e.g., panting and sweating. Increased core temperature (Tc) may result. Following rehydration and correction of fluid deficits, panting and sweating commence. We investigated the role of oropharyngeal/esophageal, postabsorptive and thermal signals in the panting response, and reduced Tc that occurs when unshorn sheep drink water following water deprivation for 2 days (ambient temperature 20°C). Ingestion of water (at body temperature) resulted in increased respiratory rate (panting) and reduced Tc within 4 min that persisted for at least 90 min. Initially, a similar panting response and reduced Tc occurred following rehydration by drinking isotonic saline solution, but panting was not sustained after 20 min, and Tc began to rise again. Rehydration by intraruminal administration of water, without any drinking, resulted in delayed panting and fall in Tc. Intraruminal infusion of saline was ineffective. Rehydration by drinking cool water (20°C) resulted in a rapid fall in Tc without increased panting. Shorn sheep had lower basal Tc that did not increase during 2 days of water deprivation, and they did not pant on rehydration by drinking water. Our results indicate that signals from the oropharyngeal and/or esophageal region associated with the act of drinking play a crucial role in the initial 20–30 min of the panting response to rehydration. Postabsorptive factors most likely reduced plasma tonicity and cause continued panting and further reduction in Tc. Tc also influences rehydration-induced panting. It occurs only if sheep incur a heat load during bodily dehydration.

scholarly journals Intact osmoregulatory centers in the preterm ovine fetus: Fos induction after an osmotic challenge

2001 â—½  
Vol 281 (6) â—½  
pp. H2626-H2635 â—½  
Author(s):  
A. Caston-Balderrama â—½  
M. J. M. Nijland â—½  
T. J. McDonald â—½  
M. G. Ross
Keyword(s):  
Hypertonic Saline â—½  
Motor Neurons â—½  
Isotonic Saline â—½  
Plasma Osmolality â—½  
Neural Pathways â—½  
Neuronal Activation â—½  
Fetal Sheep â—½  
Osmotic Challenge â—½  
Fos Expression â—½  
Vasopressin Neurons

We previously demonstrated a functional systemic dipsogenic response in the near-term fetal sheep (128–130 days; 145 days = full-term) with swallowing activity stimulated in response to central and systemic hypertonic saline. Preterm fetal sheep (110–115 days) do not consistently demonstrate swallowing in response to hypertonic stimuli, and it is unclear whether this is due to immaturity of osmoreceptor mechanisms or neuronal pathways activating swallowing motor neurons. To determine whether osmoreceptive regions in the preterm fetus are activated by changes in plasma tonicity, we examined Fos expression with immunostaining in these neurons in response to an osmotic challenge. Nine preterm fetal sheep [five hypertonic saline-treated fetuses (Hyp) and four isotonic saline-treated fetuses (Iso)] were prepared with vascular and intraperitoneal catheters. Seventy-five minutes before tissue collection, hypertonic (1.5 M) or isotonic saline was infused (12 ml/kg) via an intraperitoneal catheter to fetuses. Brains were examined for patterns of neuronal activation (demonstrated by Fos protein expression). Hyp demonstrated increases in plasma osmolality (∼10 mosmol/kg H2O) and Na concentrations (5 meq/l). Increased Fos expression was detected in Hyp in the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), median preoptic nucleus (MnPO), supraoptic (SON), and paraventricular nuclei (PVN) compared with Iso animals. Neuronal activation within the OVLT, SFO, and MnPO indicates intact osmoregulatory mechanisms, whereas activation of the SON and PVN suggests intact fetal neural pathways to arginine vasopressin neurons. These results suggest that preterm fetal swallowing insensitivity to osmotic stimuli may be due to immaturity of integrated motor neuron pathways.

Osmotic stimulation of vasopressin mRNA content in the supraoptic nucleus requires synaptic activation

1995 â—½  
Vol 268 (4) â—½  
pp. R1034-R1039 â—½  
Author(s):  
C. D. Sladek â—½  
K. Y. Fisher â—½  
H. E. Sidorowicz â—½  
J. R. Mathiasen
Keyword(s):  
Synaptic Input â—½  
Supraoptic Nucleus â—½  
Kynurenic Acid â—½  
Excitatory Amino Acid â—½  
Vasopressin Release â—½  
Amino Acid Receptors â—½  
Mrna Content â—½  
Supraoptic Neurons â—½  
Vasopressin Neurons

The role of synaptic input to the vasopressin neurons in hypertonicity-induced increase in vasopressin mRNA content was evaluated. Synaptic connection with the anterior hypothalamus is required for hypertonicity to increase vasopressin release. However, the potential for other mechanisms to induce the increase in vasopressin mRNA content is suggested by the fact that hypertonicity induces depolarization of supraoptic neurons independently of synaptic input. Explants of the hypothalamoneurohypophysial system were used to study the effect of depolarization and hypertonicity in the presence and absence of nonspecific synaptic blockade by 15 mM MgSO4 or blockade of excitatory amino acid receptors with kynurenic acid. Vasopressin release and mRNA content were increased by depolarization with 40 mM KCl and by exposure to hypertonicity (P < 0.05). Basal and osmotically stimulated vasopressin release was decreased by MgSO4 and by kynurenic acid. Both agents prevented the hypertonicity-induced increase in vasopressin mRNA content. Thus either synaptic input or increased VP release is required for hypertonicity to increase vasopressin mRNA, and excitatory amino acids are implicated in this response.

Effect of progesterone on the activation of neurones of the supraoptic nucleus during parturition

Reproduction â—½  
2000 â—½  
pp. 367-376 â—½  
Author(s):  
IA Antonijevic â—½  
JA Russell â—½  
RJ Bicknell â—½  
G Leng â—½  
AJ Douglas
Keyword(s):  
Progesterone Receptor â—½  
Supraoptic Nucleus â—½  
Late Pregnancy â—½  
Endogenous Opioids â—½  
Opioid Antagonist â—½  
Endogenous Opioid â—½  
Fos Expression â—½  
Oxytocin Neurones â—½  
Supraoptic Nuclei

Parturition is driven by a pulsatile pattern of oxytocin secretion, resulting from burst firing activity of supraoptic oxytocin neurones and reflected by induction of Fos expression. Rats were injected with progesterone on day 20 of pregnancy to investigate the role of the decreasing progesterone:ratio oestrogen ratio, which precedes delivery, in the activation of supraoptic neurones. Progesterone delayed the onset of birth by 28 h compared with vehicle (control) and prolonged the duration of delivery, which was overcome by pulsatile injections of oxytocin, indicating that the slow delivery may reflect impaired oxytocin secretion. Parturient rats pretreated with progesterone had fewer Fos immunoreactive nuclei in the supraoptic nucleus than did parturient rats pretreated with vehicle. The number of Fos immunoreactive nuclei was not restored after oxytocin injection, indicating that appropriate activation of oxytocin neurones is impaired by progesterone and also that there is a lack of stimulatory afferent drive. Fos expression increased in the nucleus of the tractus solitarius during parturition in rats pretreated with either vehicle or progesterone, but not in rats that had been pretreated with progesterone and induced with oxytocin, indicating that this input was inhibited. Endogenous opioids inhibit oxytocin neurones in late pregnancy and the opioid antagonist, naloxone, increases Fos expression in supraoptic nuclei by preventing inhibition. However, progesterone attenuated naloxone-induced Fos expression in the supraoptic nucleus in late pregnancy and naloxone administered during parturition did not accelerate the duration of births delayed by progesterone administration, indicating that progesterone does not act by hyperactivation of endogenous opioid tone. RU486, a progesterone receptor antagonist, enhanced supraoptic neurone Fos expression in late pregnancy, indicating progesterone receptor-mediated actions. Thus, progesterone withdrawal is necessary for appropriate activation of supraoptic and tractus solitarius neurones during parturition.

Central Fos expression in fetal and adult sheep after intraperitoneal hypertonic saline

1999 â—½  
Vol 276 (2) â—½  
pp. H725-H735 â—½  
Author(s):  
A. Caston-Balderrama â—½  
M. J. M. Nijland â—½  
T. J. McDonald â—½  
M. G. Ross
Keyword(s):  
Hypertonic Saline â—½  
Isotonic Saline â—½  
Plasma Osmolality â—½  
Fluid Composition â—½  
Fetal Sheep â—½  
Adult Sheep â—½  
Fos Protein â—½  
Osmotic Challenge â—½  
Fos Expression â—½  
Near Term

We hypothesized that neural structures, involved in sensing extracellular body fluid composition in adult animals during an osmotic challenge, would show similar patterns of activation in fetal sheep. Eight adult sheep [4 hypertonic saline-treated adults (HYP-A), 4 isotonic saline-treated adults] and six near-term fetal sheep [3 hypertonic saline-treated fetuses (HYP-F), 3 isotonic saline-treated fetuses; 130 days gestation] were prepared with vascular and intraperitoneal catheters. Seventy-five minutes before tissue collection, hypertonic (1.5 M) or isotonic saline was infused via an intraperitoneal catheter to adult (18 ml/kg) or fetal sheep (6 ml/kg). Brains were examined for patterns of neuronal activation (demonstrated by Fos protein expression). HYP-A and HYP-F demonstrated similar acute increases in plasma osmolality (∼10 mosmol/kgH2O) and comparable patterns of Fos expression within the organum vasculosum of the lamina terminalis (HYP-A, 67 ± 2 vs. HYP-F, 63 ± 6; means ± SE) and hypothalamic supraoptic (SON; HYP-A, 107 ± 8 vs. HYP-F, 102 ± 7) and paraventricular nuclei (PVN; HYP-A, 71 ± 18 vs. HYP-F, 124 ± 19). Fewer activated neurons were detected in HYP-A vs. HYP-F within the subfornical organ (HYP-A, 33 ± 8 vs. HYP-F, 91 ± 17) and median preoptic nucleus (HYP-A, 33 ± 5 vs. HYP-F, 70 ± 6). In adults and fetuses, counterstaining for arginine vasopressin revealed that neurons within the SON and PVN respond to osmotic challenge. These findings demonstrate that central osmoregulatory centers in adult and near-term fetal sheep are similarly activated by osmotic challenge.

Fos expression following isotonic volume expansion of the unanesthetized male rat

1998 â—½  
Vol 274 (5) â—½  
pp. R1345-R1352 â—½  
Author(s):  
R. R. Randolph â—½  
Q. Li â—½  
K. S. Curtis â—½  
M. J. Sullivan â—½  
J. T. Cunningham
Keyword(s):  
Volume Expansion â—½  
Supraoptic Nucleus â—½  
Venous Pressure â—½  
Isotonic Saline â—½  
Brain Regions â—½  
Ventrolateral Medulla â—½  
Male Rat â—½  
Double Labeling â—½  
Vasopressin Release â—½  
Fos Expression

Cardiopulmonary afferents, baroreceptor afferents, or atrial natriuretic peptide binding to circumventricular organs may mediate the central response to volume expansion, a condition common to pregnancy, exercise training, and congestive heart failure. This study used Fos immunocytochemistry to examine brain regions activated by volume expansion. Male Sprague-Dawley rats were infused with isotonic saline equal to 10% of their body weight in 10 min followed by a maintenance infusion of 0.5 ml/min for 110 min. Control animals received 2-h infusions at 0.01 ml/min. Five minutes after the start of volume expansion, central venous pressure of expanded animals was significantly greater than control animals. The volume-expanded group exhibited significantly greater Fos activation ( P < 0.05) in the area postrema, nucleus of the solitary tract, caudal ventrolateral medulla, paraventricular nucleus, supraoptic nucleus, and perinuclear zone of the supraoptic nucleus. Double labeling indicates that oxytocinergic neurons in the supraoptic nucleus are activated. Neurons in brain regions known to inhibit both sympathetic activity and vasopressin release show increased Fos expression following isotonic volume expansion.

Estrogen receptor-α expression in osmosensitive elements of the lamina terminalis: regulation by hypertonicity

2004 â—½  
Vol 287 (3) â—½  
pp. R661-R669 â—½  
Author(s):  
Suwit J. Somponpun â—½  
Alan Kim Johnson â—½  
Terry Beltz â—½  
Celia D. Sladek
Keyword(s):  
Estrogen Receptor â—½  
Body Fluid â—½  
Water Deprivation â—½  
Plasma Osmolality â—½  
Significant Degree â—½  
Estrogen Receptor Α â—½  
Male Rats â—½  
Moderate Increase â—½  
Lamina Terminalis â—½  
Double Label

The subfornical organ (SFO), median preoptic nucleus (MnPO), and organum vasculosum lamina terminalis (OVLT), which are associated with the lamina terminalis, are important in the control of body fluid balance. Neurons in these regions express estrogen receptor (ER)-α, but whether the ER-α neurons are activated by hypertonicity and whether hypertonicity regulates ER-α expression are not known. Using fluorescent, double-label immunocytochemistry, we examined the expression of ER-α-immunoreactivity (ir) and Fos-ir in control and water-deprived male rats. In control animals, numerous ER-α-positive neurons were expressed in the periphery of the SFO, in both the dorsal and ventral MnPO, and in the dorsal cap of the OVLT. Fos-positive neurons were sparse in euhydrated rats but were numerous in the SFO, MnPO, and the dorsal cap of the OVLT after 48-h water deprivation. Most ER-α-ir neurons in these areas were positive for Fos, indicating a significant degree of colocalization. To examine the effect of dehydration on ER-α expression, animals with and without lesions surrounding the anterior and ventral portion of the 3rd ventricle (AV3V) were water deprived for 48 h. Water deprivation resulted in a moderate increase in ER-α-ir in the SFO of sham-lesioned rats ( P = 0.03) and a dramatic elevation in AV3V-lesioned animals ( P < 0.05). This was probably induced by the significant increase in plasma osmolality in both dehydrated groups ( P < 0.001) rather than a decrease in blood volume, because hematocrit was significantly increased only in the dehydrated sham-lesioned animals. Thus these studies implicate the osmosensitive regions of the lamina terminalis as possible targets for sex steroid effects on body fluid homeostasis.

Role of vasopressin in cardiovascular responses to acute and chronic hyperosmolality

1992 â—½  
Vol 262 (1) â—½  
pp. R25-R32 â—½  
Author(s):  
R. D. Russ â—½  
B. L. Brizzee â—½  
B. R. Walker
Keyword(s):  
Hypertonic Saline â—½  
Water Deprivation â—½  
Peripheral Resistance â—½  
Plasma Osmolality â—½  
Cardiovascular Responses â—½  
Saline Infusion â—½  
Minor Role â—½  
Arterial Blood â—½  
Hypertonic Saline Infusion

Experiments were performed in conscious chronically instrumented rats to determine the role of arginine vasopressin (AVP) in the cardiovascular adjustments to acute and chronic increases in plasma osmolality. Animals were implanted with pulsed Doppler flow probes and arterial and venous catheters for the determination of cardiac output, mean arterial blood pressure (MABP), and heart rate and for the calculation of total peripheral resistance and baroreflex sensitivity (BRS). Before and after raising plasma osmolality by either 48-h water deprivation or acute hypertonic saline infusion, specific V1- or V2-vasopressinergic receptor antagonists or vehicle were administered to the animals, and the cardiovascular responses were noted. MABP was significantly elevated in water-deprived animals. These animals also exhibited significantly increased BRS, which was further increased by administration of the V1-receptor antagonist. Animals subjected to acute hypertonic saline infusion also demonstrated increased MABP, although the infusion, unlike water deprivation, did not affect BRS. We observed no significant effects on any other variable measured. We conclude that AVP plays a relatively minor role in the cardiovascular adjustments to acute and chronic hyperosmolality.

Sign in / Sign up

Export Citation Format

Share Document