Biomedical subjects

Eric G Krause

Publications and source records attributed to Eric G Krause.

5 recordsLinked to original sources

PubMed2006

Oestrogen and weight loss decrease isoproterenol-induced Fos immunoreactivity and angiotensin type 1 mRNA in the subfornical organ of female rats.

Studies from our laboratory and others show that oestrogen reduces angiotensin II (Ang II)-induced water intake by ovariectomized rats. Elimination of endogenous oestrogen by ovariectomy causes weight gain that can be reversed or prevented by oestrogen replacement. Changes in body weight modify cardiovascular responses to Ang II but whether such changes have similar effects on central and behavioural responses to Ang II is unknown. The goal of this study was to evaluate the contributions of oestrogen and weight loss to isoproterenol (isoprenaline; Iso)-induced Fos immunoreactivity (IR) and to angiotensin type 1 (AT1) receptor mRNA in forebrain regions implicated in the control of fluid balance. Isoproterenol significantly increased Fos IR in the hypothalamic paraventricular and supraoptic nuclei, the subfornical organ (SFO), and the organum vasculosum of the lamina terminalis, but had no effect on AT1 mRNA expression. However, both Iso-induced Fos IR and the AT1 mRNA were attenuated in the SFO of the oestrogen and weight loss groups compared with that of the control group. Consequently, we examined the effect of weight loss on Iso-induced water intake and plasma renin activity (PRA) and found that weight loss decreased water intake after Iso, but had no effect on PRA. Thus, we propose that weight loss decreases Ang II-elicited water intake in the female rat by down-regulating the expression of the AT1 receptor.

Animals↗

PubMed2004

Gestational and early postnatal dietary NaCl levels affect NaCl intake, but not stimulated water intake, by adult rats.

We examined body fluid regulation by weanling (21-25 days) and adult (>60 days) male rats that were offspring of dams fed chow containing either 0.1, 1, or 3% NaCl throughout gestation and lactation. Weanling rats were maintained on the test diets until postnatal day 30 and on standard 1% NaCl chow thereafter. Ad libitum water intake by weanlings was highest in those fed 3% NaCl and lowest in those fed 0.1% NaCl. Adult rats maintained on standard NaCl chow consumed similar amounts of water after overnight water deprivation or intravenous hypertonic NaCl (HS) infusion regardless of early NaCl condition. Moreover, baseline and HS-stimulated plasma Na(+) concentrations also were similar for the three groups. Nonetheless, adult rats in the early 3% NaCl group consumed more of 0.5 M NaCl after 10 days of dietary Na(+) deprivation than did rats in either the 1% or 0.1% NaCl group. Interestingly, whether NaCl was consumed in a concentrated solution in short-term, two-bottle tests after dietary Na(+) deprivation or in chow during ad libitum feeding, adult rats in the 3% NaCl group drank less water for each unit of NaCl consumed, whereas rats in the 0.1% NaCl group drank more water for each unit of NaCl consumed. Thus gestational and early postnatal dietary NaCl levels do not affect stimulated water intake or long-term body fluid regulation. Together with our previous studies, these results suggest that persistent changes in NaCl intake and in water intake associated with NaCl ingestion reflect short-term behavioral effects that may be attributable to differences in NaCl taste processing.

Aging↗

PubMed2003

Cardiovascular function and circadian patterns in rats after area postrema lesions or prolonged food restriction.

The role of the area postrema (AP) in baseline cardiovascular function was evaluated by radio telemetry in rats with lesions of AP (APX), along with the effect of APX on circadian patterns of cardiovascular function and ingestive behavior. Despite lesion-induced hypophagia and body weight loss, APX did not affect circadian patterns of mean arterial pressure (MAP), heart rate (HR), or ingestion but did cause a substantial decrease (-60 bpm) in resting HR. The bradycardia was not attributable to weight loss, as resting HR in weight-matched controls, though decreased from baseline, was significantly greater than that in rats with APX. In weight-matched controls, HR increased slightly when weight returned to baseline; however, the bradycardia persisted in rats with APX. These results suggest that AP contributes to resting HR, independent of weight loss or changes in circadian patterns of HR or MAP.

Animals↗

PubMed2003

Estrogen influences stimulated water intake by ovariectomized female rats.

To further elucidate the influence of estrogen on water consumption, we examined water intake by adult female rats stimulated by water deprivation, injection of hypertonic saline or injection of isoproterenol (ISOP), a beta-adrenergic agonist that activates the renin-angiotensin system (RAS). Rats were ovariectomized (OVX) then injected with estradiol benzoate (EB; 10 microg/0.1 ml oil) or the oil vehicle (OIL; 0.1 ml) for 2 consecutive days. Twenty-four hours after the second injection, rats were deprived of food and water. On the following day, rats were given water and intake was measured after 2 h. EB significantly decreased water intake compared with that by OIL-treated rats following water deprivation. Two additional groups of adult female rats were OVX and treated with EB or OIL. Forty-eight hours after EB or OIL treatment, rats were injected with hypertonic saline (1 ml of 2 M NaCl) or ISOP (30 microg/kg in 0.15 M saline) and water intake was measured after 2 h. EB significantly attenuated water intake following ISOP but not after hypertonic saline. Finally, we examined plasma sodium concentration (pNa) after hypertonic saline and plasma renin activity (PRA) after ISOP in EB- and OIL-treated rats and found no differences in pNa or PRA. These results suggest that the stimuli for water intake after hypertonic saline and ISOP were comparable in EB- and OIL-treated rats. Taken together, these results raise the possibility that EB attenuation of stimulated water intake is specific to water intake elicited by activation of the RAS.

Adrenergic beta-Agonists↗

PubMed2002

Fos expression in non-catecholaminergic neurons in medullary and pontine nuclei after volume depletion induced by polyethylene glycol.

Fos immunocytochemistry was combined with immunolabeling for dopamine-beta-hydroxylase (DBH) to examine neuronal activation in the medulla and pons after administration of polyethelene glycol (PEG), which produces volume depletion without altering arterial blood pressure. Increased Fos immunoreactivity was observed in the area postrema, nucleus of the solitary tract, rostral ventrolateral medulla, lateral parabrachial nucleus, and the dorsomedial pons at the level of the locus coeruleus. Fos immunolabeling in the caudal nucleus of the solitary tract, rostral ventrolateral medulla, and the dorsomedial pons occurred primarily in neurons that did not contain DBH. Thus, PEG activates non-catecholaminergic neurons in medullary and pontine areas associated with cardiovascular and body fluid regulation.

Animals↗