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

Abstract

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.

Combined estrogen and ghrelin administration restores number of blood vessels and collagen type I/III ratio in the urethral and anal canal submucosa of old ovariectomized rats

“…The age-adjusted body weight in ad libitum fed rats is significantly greater in Wistar rats than in Fisher 344 rats [27]. Although we did not measure physical activity or basal metabolism in the previous or present study, exogenous administration of estrogen and/or ghrelin has also been reported to alter food intake and consequently body weight in rats [26,28].…”

“…The different age of the old subgroup and species of the animal model (13 months old Wistar rats vs 18 months old Fisher 344 rats) could be responsible. It is also possible that body weight affects the target tissue vascular response to estrogen and ghrelin in rats similar to other cardiovascular control functions such as the renin-angiotensin system [26]. The age-adjusted body weight in ad libitum fed rats is significantly greater in Wistar rats than in Fisher 344 rats [27].…”

Blood-Borne Angiotensin II Acts in the Brain to Influence Behavioral and Endocrine Responses to Psychogenic Stress

“…The c-fos fragment (original full-length cDNA from T. Curran, St. Jude Children’s Research Hospital, Memphis, TN) was cloned into a TOPO PCR vector (Invitrogen, Carlsbad, CA), linearized with Hind III, and transcribed with T3 RNA polymerase. Pretreatment of slides, hybridization, post-treatment and image analysis were performed as previously described (Krause et al, 2006). …”

Time course of behavioral, physiological, and morphological changes after estradiol treatment of ovariectomized rats

“…In fact, accumulating evidence supports the idea that estrogens reduce ‘volemic thirst’ — fluid intake stimulated by activation of the renin–angiotensin system. We and others have reported that, in rats, estrogens attenuate water intake stimulated by isoproterenol [19,20,30,32,61], a β-adrenergic agonist that produces a robust increase in circulating levels of angiotensin II (AngII). Importantly, the reduction of isoproterenol-induced drinking by estradiol-treated ovariectomized rats occurs despite comparable elevations in AngII [30].…”

“…Neuronal activation in response to isoproterenol differs in specific central nuclei, depending on whether ovariectomized rats are treated with estradiol [26,31,32]. In this regard, estrogens are highly lipophilic and can easily access estrogen receptors (ERs) located throughout the CNS, particularly in areas involved in body fluid balance [2,24,45,50,51,53,54,59,60,62].…”