Distribution of Fos-immunoreactivity in rat brain following a dipsogenic dose of captopril and effects of angiotensin receptor blockade

Immunohistochemical techniques were used to detect Fos in the brain following subcutaneous administration of the angiotensin converting enzyme inhibitors captopril or enalapril at 0.5 mg/kg to conscious rats. Increased Fos-like immunoreactivity was observed in many neurons in the lamina terminalis, and in regions of the hypothalamus. Captopril at this dose also caused water drinking in other rats. Pre-treatment with the angiotensin AT1 receptor antagonist ZD7155 (10 mg/kg) given subcutaneously prevented the captopril-induced increase in Fos in the lamina terminalis. This dose of ZD7155 also prevented captopril-induced drinking in other rats. With a higher dose (50 mg/kg) of captopril or enalapril, there was no increase in Fos in the lamina terminalis. This dose of captopril was not dipsogenic. The results are consistent with the proposal that the lower dose (0.5 mg/kg) of captopril or enalapril increases circulating angiotensin I levels which are then converted to angiotensin II in the organum vasculosum of the lamina terminalis and subfornical organ. Stimulation of neurons at these sites may subserve water drinking and sodium appetite.

Centrally administered losartan inhibits the reduction in plasma renin concentration caused by intracerebroventricular hypertonic saline in Na-depleted sheep

Infusions (at 1 ml/h) of two different hypertonic solutions were made into the lateral cerebral ventricle of Na-depleted sheep and the effect on plasma renin concentration (PRC) was investigated. Intracerebroventricular (i.c.v.) infusion of 0.75 mol/l NaCl caused a large reduction in plasma renin concentration whereas i.c.v. infusions of hypertonic 1.2 mol/l sorbitol in 0.15 mol/l NaCl or isotonic artificial cerebrospinal fluid did not. An i.c.v. infusion of the angiotensin AT1 receptor antagonist losartan (1 mg/ml per h for 2.5 h) commencing 1 h prior to i.c.v. 0.75 mol/l NaCl prevented the reduction in PRC induced by i.c.v. hypertonic NaCl. No change in arterial pressure occurred with any of these i.c.v. infusions in Na-depleted sheep. The results suggest that a central angiotensinergic mechanism may be involved in central pathways inhibiting renin secretion by the kidney.

The role of angiotensin II in ingestive behaviour: a brief review of angiotensin II, thirst and Na appetite

From the outset, the study of angiotensin II (Ang II) in body fluid homeostasis has been both complicated and intriguing. Since the publication of an early report of the dipsogenic action of this peptide, the pursuit of the role of Ang II in thirst and Na appetite has continued for the last 25 years. This pursuit captured the attention of all workers interested in the behavioural/physiological regulation of body fluid balance, with major contributions being made by James T. Fitzsimons and his colleagues. In spite of its powerful dipsogenic actions, delineation of its precise role in physiological thirst has been elusive and difficult to demonstrate. The influence of Ang II on Na intake took longer to show convincingly. However, in contrast to thirst, the role of Ang II in physiological Na appetite has been demonstrated clearly. The technological advances made during the recent years have greatly increased our ability to delineate the neurobiological context of Ang II-mediated responses. Thus, the future is promising in regard to illuminating the subtleties of the role of Ang II in body fluid balance.

Increased oxidative stress and decreased antioxidant defenses in mucosa of inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by chronic intestinal inflammation whose cellular components are capable of oxidative respiratory bursts that may result in tissue injury. Mucosal biopsies were analyzed for protein carbonyl content (POPs), DNA oxidation products [8-hydroxy-2'-deoxyguanosine (8-OHdG)], reactive oxygen intermediates (ROIs), trace metals (copper, zinc, and iron) and superoxide dismutase (Cu-Zn SOD). In Crohn's disease biopsies, there was an increase in ROIs, POPs, 8-OHdG, and iron, while decreased copper and Cu-Zn SOD activity were found in inflamed tissues compared to controls. For ulcerative colitis, there was an increase in ROIs, POPs, and iron in inflamed tissue compared to controls, while decreased zinc and copper were observed. An imbalance in the formation of reactive oxygen species and antioxidant micronutrients may be important in the pathogenesis and/or perpetuation of the tissue injury in IBD and may provide a rationale for therapeutic modulation with antioxidants.

Hypothalamic integration of body fluid regulation

The progression of animal life from the paleozoic ocean to rivers and diverse econiches on the planet's surface, as well as the subsequent reinvasion of the ocean, involved many different stresses on ionic pattern, osmotic pressure, and volume of the extracellular fluid bathing body cells. The relatively constant ionic pattern of vertebrates reflects a genetic "set" of many regulatory mechanisms--particularly renal regulation. Renal regulation of ionic pattern when loss of fluid from the body is disproportionate relative to the extracellular fluid composition (e.g., gastric juice with vomiting and pancreatic secretion with diarrhea) makes manifest that a mechanism to produce a biologically relatively inactive extracellular anion HCO3- exists, whereas no comparable mechanism to produce a biologically inactive cation has evolved. Life in the ocean, which has three times the sodium concentration of extracellular fluid, involves quite different osmoregulatory stress to that in freshwater. Terrestrial life involves risk of desiccation and, in large areas of the planet, salt deficiency. Mechanisms integrated in the hypothalamus (the evolutionary ancient midbrain) control water retention and facilitate excretion of sodium, and also control the secretion of renin by the kidney. Over and above the multifactorial processes of excretion, hypothalamic sensors reacting to sodium concentration, as well as circumventricular organs sensors reacting to osmotic pressure and angiotensin II, subserve genesis of sodium hunger and thirst. These behaviors spectacularly augment the adaptive capacities of animals. Instinct (genotypic memory) and learning (phenotypic memory) are melded to give specific behavior apt to the metabolic status of the animal. The sensations, compelling emotions, and intentions generated by these vegetative systems focus the issue of the phylogenetic emergence of consciousness and whether primal awareness initially came from the interoreceptors and vegetative systems rather than the distance receptors.

Identification of osmoresponsive neurons in the forebrain of the rat: a Fos study at the ultrastructural level

The aims of this study are twofold. The first is to describe the ultrastructural morphology of putative osmoreceptors concentrated in the ventral aspect of the lamina terminalis in the rat forebrain. The second is to determine whether or not these neurons lie within an area which lacks a blood-brain barrier, i.e. the organum vasculosum lamina terminalis. The results describe a compact population of neurons in the ventral part of the lamina terminalis which both respond to an osmotic challenge and project directly to the supraoptic nucleus. Injection of horseradish peroxidase into the circulation, as a marker to define areas of the brain without a blood-brain barrier, indicates that these neurons are in the dorsal aspect of the organum vasculosum of the lamina terminalis. An ultrastructural analysis of the neurons in this area, which respond to an osmotic challenge with an elevation of Fos protein, show them to have no specific morphological characteristics which differentiate them from other, non-responsive neurons in the organum vasculosum of the lamina terminalis. However, one possible exception is that osmotically sensitive neurons have a less indented nucleus, suggesting that they are in a more active state than their non-osmotically sensitive neighbours. It is concluded that neurons in this region of the brain are candidate structures for the "receptors" which mediate vasopressin release in response to an osmotic challenge. The response of only a subset of neurons in the organum vasculosum of the lamina terminalis to an osmotic stimulus, despite an apparent morphological homogeneity and the ability of blood borne agents to reach all parts of the structure suggests that osmoresponsiveness is conferred by unique membrane properties or intracellular processing events. The presence of synaptic input to osmoresponsive cells indicates a potential for integration of other inputs at this level.

Anteroventral wall of the third ventricle and dorsal lamina terminalis: headquarters for control of body fluid homeostasis?

1. The subfornical organ, median preoptic nucleus and the organum vasculosum of the lamina terminalis (OVLT) are a series of structures situated in the anterior wall of the third ventricle and form the lamina terminalis. The OVLT and ventral part of the median preoptic nucleus are part of a region known as the anteroventral third ventricle region. 2. Data from many laboratories, using techniques ranging from lesions, electrophysiology, neuropharmacology, Fos expression, immunohistochemistry and receptor localization, indicate that the tissue in the lamina terminalis plays a major role in many aspects of body fluid and electrolyte balance. 3. The subfornical organ and OVLT lack the blood-brain barrier and detect alterations in plasma tonicity and the concentrations of circulating hormones such as angiotensin II and possibly atrial natriuretic peptide and relaxin. 4. This information is then integrated within the lamina terminalis (probably in the median preoptic nucleus) with neural signals from other brain regions. The neural output from the lamina terminalis is distributed to a number of effector sites including the paraventricular (both parvo- and magno-cellular parts) and supraoptic nuclei and influences vasopressin secretion, water drinking, salt intake, renin secretion, renal sodium excretion and cardiovascular regulation.

Localization of angiotensin IV binding sites to motor and sensory neurons in the sheep spinal cord and hindbrain

In the sheep spinal cord, a high density of [125I]angiotensin IV binding sites was localized to the perikaryon and processes of all somatic motor neurons, the autonomic motor neurons in the lateral horns of thoracic and lumbar segments and all dorsal root ganglia, but was low in lamina II of all dorsal horns. At supraspinal levels, [125I]angiotensin IV binding was abundant in numerous motor associated regions, with weaker binding observed in the sensory regions. This wide distribution pattern suggests an important role for the binding site in the central nervous system.

Localization of angiotensin converting enzyme by in vitro autoradiography in the rabbit brain

The distribution of angiotensin converting enzyme was examined in the rabbit brain by in vitro autoradiography with the specific radiolabelled inhibitor 125I-351A. In the rabbit, the highest concentrations of radioligand binding were found in the choroid plexus, blood vessels, subfornical organ, vascular organ of the lamina terminalis, area postrema and inferior olive. High levels of binding were found throughout the basal ganglia, consistent with the results in all other species studied. In the midbrain the central gray and the superior colliculus displayed high levels of binding. In the medulla oblongata high levels of binding were associated with the nucleus of the solitary tract and dorsal motor nucleus of vagus, consistent with the pattern in other species. There was moderate labelling throughout both the cerebral and cerebellar cortices, which contrasts to the rat but is consistent with the situation in primates. Angiotensin converting enzyme (ACE) is more widely distributed in rabbit brain that in rat, human and Macaca fascicularis, and the results suggest ACE has a very general role in the metabolism of neuropeptides. Inhibitors of converting enzyme are very widely used in the treatment of hypertension and heart disease, and the rabbit should provide a useful model for examining the effects of these drugs in the brain.

Comparison of c-fos expression in the lamina terminalis of conscious rats after intravenous or intracerebroventricular angiotensin

Fos immunoreactivity in the rat brain after intracerebroventricular (ICV) angiotensin II (ANG II) was compared with that induced by intravenous ANG II. ANG II was infused into the lateral ventricle (at 1 ng/min) or femoral vein (at 5 micrograms/h) of conscious rats. After 90 min, rats were killed and Fos was detected by immunohistochemistry. Both infusions caused Fos immunoreactivity to be present in the lamina terminalis, hypothalamic supraoptic, and paraventricular nuclei, bed nucleus of the stria terminalis, and central amygdaloid nucleus. However, distributions of Fos immunoreactivity within the lamina terminalis differed with the different routes of infusion. Intravenous ANG II caused intense Fos immunoreactivity mainly in the subfornical organ (SFO) and organum vasculosum of the lamina terminalis (OVLT). By contrast, ICV ANG II caused intense Fos immunoreactivity predominantly in the median preoptic nucleus and juxtaventricular neurons of the SFO and OVLT. These results suggest that IV ANG II induces behavioural and endocrine responses by direct actions on the SFO and OVLT, whereas ICV ANG II directly stimulates neurons in the median preoptic nucleus as well neurons in the SFO and OVLT.

Effects of central losartan on plasma renin and centrally mediated natriuresis

Because intracerebroventricular (ICV) infusion of hypertonic saline or angiotensin II (Ang II) both induce water drinking, vasopressin secretion, natriuresis and increased arterial pressure, the possibility that common neural pathways mediate responses to ICV Ang II and hypertonic saline has been investigated. This was done by testing the effect of ICV infusion of the Ang II antagonist losartan on the natriuretic and pressor responses to ICV hypertonic NaCl in sheep. The effect of ICV losartan on plasma renin concentration (PRC) was also investigated. Infusion of losartan (1 mg/hr) into a lateral ventricle prevented both natriuretic and pressor responses to infusion of 0.6 mol/liter NaCl into a lateral ventricle at 1 ml/hr. In another experiment, ICV losartan at 1 mg/hr caused a pronounced increase in the PRC of Na-depleted sheep, while ICV Ang II at 3 micrograms/hr decreased PRC. The results suggest that: (i) a central angiotensinergic pathway may mediate osmoregulatory responses to centrally administered hypertonic saline, and (ii) a central angiotensinergic pathway may have a tonic inhibitory influence on renin secretion in Na-depleted animals.

Distribution of Fos in rat brain resulting from endogenously-generated angiotensin II

The beta adrenergic agonist isoproterenol has been used in these studies to elevate circulating levels of angiotensin II. Neurons in the brain responsive to the subcutaneous infusion of isoproterenol were identified using an antibody to Fos, the protein product of c-fos which is now used extensively as a marker of activated neurons. Fos-positive neurons were present in a range of specific forebrain and hind brain regions. Infusion of losartan (an angiotensin II type receptor antagonist) showed that neurons in the lamina terminalis were activated directly or indirectly by angiotensin II, whereas other neurons in the hypothalamus and brain stem were responsive as a consequence of the peripheral vasodilation caused by isoproterenol. The distribution of activated neurons in the lamina terminalis was consistent with that of neurons thought to be involved in water drinking.

Cerebral osmoregulatory reduction of plasma renin concentration in sheep

A centrally mediated inhibitory influence of plasma hypertonicity on renin secretion was investigated in conscious, Na-depleted sheep. Infusions of hypertonic solutions were made into the carotid artery or jugular vein, and the effects on plasma renin concentration (PRC) compared. Intracarotid infusion of 1.65 M NaCl significantly reduced PRC (to 74% of the pre-infusion value) within 15 min of the commencement of the infusion whereas corresponding intrajugular infusion did not. Intracarotid infusion of 3 M sorbitol for 45 min also reduced PRC (to 64% of the pre-infusion level) significantly after 15 min of infusion. By contrast, neither intrajugular infusion of 3 M sorbitol, nor intracarotid infusion of isotonic 0.15 M NaCl for 45 min significantly reduced PRC. Intracarotid infusion of hypertonic sorbitol for 45 min did not inhibit PRC in sheep with cerebral lesions of the lamina terminalis. These results show that plasma hypertonicity may have an inhibitory influence on renin secretion. The inhibition is probably mediated by an effect of hypertonicity on the CNS, rather than a direct effect on the kidney.

Localization of barosensitive neurons in the caudal ventrolateral medulla which project to the rostral ventrolateral medulla

A population of depressor neurons in the caudal ventrolateral medulla that project to the rostral ventrolateral medulla may mediate the baroreceptor reflex. The aim of the present study was to determine the anatomical distribution of the population of neurons in the caudal ventrolateral medulla that mediate the baroreceptor reflex. Injection of the retrogradely transported tracer, rhodamine-labelled latex beads, into the pressor area of the rostral ventrolateral medulla of rats was used to identify neurons in the caudal ventrolateral medulla with projections to that area. Barosensitive neurons were identified by immunohistochemical detection of the protein Fos, a marker of neuronal activation, following infusion of the pressor agent phenylephrine (10 micrograms/kg/min, i.v. for 2 h n = 5). Isotonic saline was infused into control animals (n = 4). Neurons in the caudal ventrolateral medulla with projections to the rostral ventrolateral medulla were located at all rostrocaudal levels examined between 1 mm caudal and 0.4 mm rostral of the obex. Compared to saline infused rats, phenylephrine infusion induced a significant increase in the proportion of those neurons that expressed Fos (14% vs. 1% P < 0.000.1). These barosensitive neurons were found mainly at the level of the obex, between the lateral reticular nucleus and the nucleus ambiguus. In conclusion, this study is the first to show the distribution of the population of barosensitive neurons in the caudal ventrolateral medulla that project to the pressor region of the rostroventrolateral medulla. The results suggest there is a subpopulation of depressor neurons, confined to a small region of the rostral part of the caudal ventrolateral medulla, that are likely to be the interneurons that mediate the baroreceptor-reflex response.

Improved body weight status as a result of nutrition intervention in adult, HIV-positive outpatients

OBJECTIVE

Malnutrition is an important consequence of infection with the human immunodeficiency virus (HIV); involuntary weight loss greater than 10% is one criterion that the Centers for Disease Control and Prevention uses for the diagnosis of acquired immunodeficiency syndrome (AIDS). This study was designed to determine whether nutrition intervention in a group of adult, HIV-positive outpatients affected weight maintenance.

METHODS

We undertook a retrospective review of 175 patient charts from the AIDS Reproductive Health Clinic and the Center for Special Studies at The New York Hospital. Forty-nine charts were excluded because the patient expressed a desire to reduce weight, discontinued medical care, or died. Seven charts were eliminated because of missing data. In the remaining patients (n = 119), weights were recorded for the initial clinic contact and for a follow-up visit at least 6 months later. Nutrition intervention completed by a registered dietitian was indicated on 42 patient charts (intervention group); intervention included dietary assessment, intake analysis, appropriate counselling, follow-up, and provision of supplements as needed. The remaining 77 charts did not indicate nutrition intervention; this group was called the nonintervention group. Differences between the intervention and nonintervention groups were analyzed using the two-tailed Fisher exact test and the Mann-Whitney nonparametric test.

RESULTS

Forty-two subjects (35% of the total) recieved nutrition intervention, including all of those with gastrointestinal problems (n = 10) and wasting (n = 11). Individuals in the intervention group gained a significant (P < .02) 1.2 +/- 11.4 lb (mean +/- standard deviation; median = +3 lb) compared with those in the nonintervention group who lost a mean of 3.5 +/- 12.8 lb (median = -4 lb). Twenty-six subjects (63%) in the intervention group maintained or gained weight compared with 32 subjects (42%), in the nonintervention group.

CONCLUSION

The results of this study suggest that nutrition intervention in HIV-infected persons can improve nutritional status and may lead to an enhanced ability to fight infection.

Identification of neural pathways activated in dehydrated rats by means of Fos-immunohistochemistry and neural tracing

The distribution of Fos-immunoreactivity (Fos-IR) was studied in the brains of rats deprived of water for 24 or 48 h and compared with that in brains of water-replete rats. Intense Fos-IR was observed in many neurons of the median preoptic nucleus (MnPO), organum vasculosum of the lamina terminalis (OVLT), supraoptic nucleus and hypothalamic paraventricular nucleus. There was less intense and sparse Fos-IR in the subfornical organ. In water-replete rats, Fos-IR was absent or very low in these regions. In other rats, cholera toxin B-gold conjugate was microinjected bilaterally into the supraoptic nucleus to identify retrogradely labelled neurons in the lamina terminalis projecting to the supraoptic nucleus. Approximately 30% of these retrogradely labelled neurons in the OVLT and MnPO also exhibited Fos-IR after 48 h of water deprivation. These data show that neurons in the MnPO, OVLT and, to a lesser extent, the subfornical organ probably play an important role in homeostatic responses to dehydration, such as vasopressin secretion.

Reducing brain sodium concentration prevents post-prandial and dehydration-induced natriuresis in sheep

Renal Na excretion during the 24 h following feeding was studied in sheep. A pronounced natriuresis occurred 3.5-5.5 h after feeding. Na excretion then fell to low levels in animals allowed to drink water, but was significantly elevated above this level in water-deprived sheep for most of the remaining period. Both the post-prandial and dehydration-induced natriuresis were prevented by intracerebroventricular (icv) infusions of low Na concentration 0.3 mol l-1 mannitol at 1 ml h-1, and a water diuresis also occurred. These effects were not caused by icv infusion of artificial cerebrospinal fluid (Na concentration = 150 mmol l-1). As a result, there was a much greater increase in plasma Na concentration and osmolality in the sheep given icv mannitol. Intravenous infusion of vasopressin prevented the water diuresis induced by icv mannitol, but the inhibition of natriuresis was still observed and plasma Na concentration increased by 8 mmol l-1 over 24 h compared with an increase of 3 mmol l-1 in dehydrated sheep infused icv with artificial cerebrospinal fluid. The results show that the ambient Na concentration in the brain plays an important role in the normal homeostatic regulation of Na balance by the kidney in sheep.

Distribution of angiotensin II receptor binding in the spinal cord of the sheep

The distribution of angiotensin II binding sites has been mapped at segmental levels throughout the spinal cord of the sheep using in vitro autoradiographic methods. Binding of 125I-[Sar1.Ile8] Ang II is most prominent in the lateral horns of the thoracolumbar and sacral regions containing the sympathetic and parasympathetic preganglionic neurons respectively. Binding is also present in the dorsal horns of the grey matter, in the central canal region, dorsal root ganglia and associated with non-neuronal elements such as the ependyma surrounding the central canal, and blood vessels. Displacement with receptor antagonists specific for AT1 and AT2 subtypes, indicates that angiotensin II receptors in the spinal cord are of the AT1 type. These data help to interpret the physiological actions of angiotensin II in the spinal cord, particularly with respect to its autonomic components.

Fos production in retrogradely labelled neurons of the lamina terminalis following intravenous infusion of either hypertonic saline or angiotensin II

The lamina terminalis consists of neurons which are activated by both osmotic and angiotensinergic stimuli and which project axons to many sites including regions of the hypothalamus responsible for vasopressin production. Combination of retrograde neuronal tracing procedures with the identification of Fos protein following discrete stimuli shows populations of neurons, projecting to the supraoptic nuclei, which are preferentially activated by intravenous infusion of either hypertonic saline or angiotensin II. Following infusion of hypertonic saline, the greatest percentage of neurons both labelled with cholera toxin-gold and having elevated levels of Fos protein occurred in that part of the lamina terminalis called the organum vasculosum lamina terminalis. Conversely, angiotensin infusion resulted in greatest numbers of Fos and cholera toxin-gold-labelled neurons in the subfornical organ with fewer double-labelled cells represented in the other components of the lamina terminalis, the median preoptic nucleus and the organum vasculosum lamina terminalis. While these data do not support more than a general separation of the functions examined among neurons of the lamina terminalis, they do highlight a discrete group of osmoresponsive neurons in the dorsal cap of the organum vasculosum lamina terminalis. These cells, by virtue of their response to infusions of hypertonic saline and their axonal connections to regions of the hypothalamus responsible for vasopressin production, are likely candidates for cerebral osmoreceptors.

Marked gamma delta T-cell decrease in peripheral blood of patients with primary biliary cirrhosis (PBC)

PBC is a cholestatic liver disease of unknown etiology with autoimmune features that is often associated with other autoimmune diseases. We analyzed peripheral blood T-cell subsets in patients groups with PBC (n = 11), non-PBC hepatobiliary disease (n = 11) and an age and sex matched control group (n = 11) by two color FACS-analysis. Seven out of eleven PBC patients exhibited markedly lowered and nearly undetectable levels of gamma delta T-cells (< 0.8%). None of the individuals in the non-PBC hepatobiliary disease (HBD) group or the normal control group had gamma delta values below 1%. The other four individuals in the PBC group had gamma delta values within the normal range. Overall, the PBC group had a statistically significant, lowered mean percentage of gamma delta T-cells (1.50%) as compared to the hepatobiliary disease group (3.76%) and the control group (4.22%, p = 0.01). The percentages of CD4+ and CD8+ and alpha beta TCR+ CD4-CD8- double negative cells in PBC patients did not differ from the control group. PBC patients with normal gamma delta cell counts did not differ from the PBC group with low gamma delta values in autoantibody titers, liver tests or treatment of the disease. As a possible cause for the observed decrease of gamma delta T-cells three sera of PBC patients with low gamma delta T-cell counts were screened by single color, indirect immunofluorescence for antibodies to gamma delta T-cell enriched lymphocytes, but no differences to control sera were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Forebrain lesions that disrupt water homeostasis do not eliminate the sodium appetite of sodium deficiency in sheep

Brain structures located within the anterior wall of the third brain ventricle (subfornical organ, median preoptic nucleus and organum vasculosum of the lamina terminalis) are known to be involved in thirst as well as other aspects of body fluid and electrolyte balance. The present studies evaluated the role of these structures in the Na appetite of mildly or moderately Na-depleted sheep (sheep with a parotid fistula deprived of Na solution for 22 or 46 h). In addition, the role of these structures was tested in mildly Na-depleted sheep in which the Na appetite was enhanced by decreasing cerebrospinal fluid and brain extracellular fluid Na concentration (i.e., i.c.v. infusion of hypertonic saccharide solution) or was decreased by systemic infusion of hypertonic saline. The results indicated that sheep with lesions which reduced or eliminated daily water intake or water intake in response to hypertonicity of body fluids had, in all situations tested, appropriate changes in Na appetite (i.e., similar to their prelesion changes). Thus, the present experiments demonstrated that the brain areas involved in thirst as well as other aspects of body fluid and electrolyte balance are anatomically different from those involved in regulating Na appetite.

Haemorrhage-induced production of Fos in neurons of the lamina terminalis: role of endogenous angiotensin II

Hypotensive haemorrhage increased the production of Fos, a marker of cell activation, in cells of the subfornical organ (SFO) and the organum vasculosum of the lamina terminalis (OVLT) as well as in the supraoptic (SON) and paraventricular (PVN) nuclei in conscious rats. Pretreatment with captopril (100 mg/kg i.p.) inhibited the production of Fos in cells of the SFO and OVLT but did not reduce the concentration of Fos-positive cell nuclei in the PVN and SON. The results suggest that the production of Fos in the SFO and OVLT induced by the haemorrhage is probably due to elevated levels of circulating angiotensin II.