Forebrain circumventricular organs mediate captopril-enhanced ethanol intake in rats

Sexual Dimorphism in the Expression of Cardiac and Hippocampal Renin-Angiotensin and Kallikrein–Kinin Systems in Offspring from Mice Exposed to Alcohol during Gestation

Prenatal alcohol exposure (PAE) impairs fetal development. Alcohol consumption was shown to modulate the renin–angiotensin system (RAS). This study aimed to analyze the effects of PAE on the expression of the renin–angiotensin system (RAS) and kallikrein–kinin system (KKS) peptide systems in the hippocampus and heart of mice of both sexes. C57Bl/6 mice were exposed to alcohol during pregnancy at a concentration of 10% (v/v). On postnatal day 45 (PN45), mouse hippocampi and left ventricles (LV) were collected and processed for messenger RNA (mRNA) expression of components of the RAS and KKS. In PAE animals, more pronounced expression of AT1 and ACE mRNAs in males and a restored AT2 mRNA expression in females were observed in both tissues. In LV, increased AT2, ACE2, and B2 mRNA expressions were also observed in PAE females. Furthermore, high levels of H2O2 were observed in males from the PAE group in both tissues. Taken together, our results suggest that modulation of the expression of these peptidergic systems in PAE females may make them less susceptible to the effects of alcohol.

Role of angiotensin II and the subfornical organ in the pharmacological actions of ethanol

AIMS

The current study was designed to evaluate if angiotensin II mediates the hypothermic effects of ethanol, and to determine if the effects of angiotensin are mediated centrally. We also tested the hypothesis that the subfornical organ (SFO) is a site responsible for the alterations in body temperature and aerial righting reflex mediated by ethanol and for the modulation of ethanol consumption in rats.

METHODS

Male Sprague-Dawley rats were used in a series of experiments to evaluate the role of both peripheral and central administration of losartan, a selective angiotensin type 1 receptor antagonist on ethanol-induced hypothermia. Subsequent studies were undertaken in SFO-lesioned rats to evaluate the effects of SFO-lesion on alcohol intake, the thermal response to alcohol and angiotensin, and the aerial righting reflex.

RESULTS

Selective antagonism of the angiotensin II type 1 receptor, administered either peripherally or centrally, attenuated not only the fall in colonic temperature but also attenuated the transient rise in tail skin temperature that was associated with administration of ethanol. The thermal responses to both angiotensin and ethanol were similarly attenuated in SFO-lesioned rats. Likewise the aerial righting reflex, which has previously been shown to be impaired by losartan treatment, was also significantly attenuated in SFO-lesioned animals. Alcohol intake, as determined by a 48 h, two-bottle preference test also revealed that SFO-lesioned animals consumed significantly less alcohol (ethanolic beer) than did controls.

CONCLUSION

Collectively, the results demonstrate that ethanol-induced temperature responses are mediated by the renin-angiotensin system and that this interaction is mediated centrally. In addition, the results demonstrate that the SFO is a site that mediates several neurobiological effects of ethanol, possibly via the renin-angiotensin system.

Angiotensin II stimulates intake of ethanol in C57BL/6J mice

The influence of intracerebroventricular (i.c.v.) infusion of angiotensin II on intake of water and ethanol solutions was determined in C57BL/6J mice. Compared to other mice, C57 mice do not show an aversion to ethanol solutions. With both water and ethanol solutions available, the C57 mice consumed 40-60% of their total daily fluid intake as ethanol solution when the concentration of ethanol solution offered was 4-14%. When given a choice between 0.3 M KCl and either 4 or 10% ethanol solution, the mice clearly preferred the ethanol solution. With water only available, i.c.v. infusion of angiotensin II increased intake from 3-5 mL/day (baseline) to 11-12 mL/ day (Day 4 of infusion). A similar increase in intake occurred in mice with access to a nonpreferred solution of 0.3 M KCl. In comparison, when only 4% ethanol solution was available, angiotensin II increased intake to 7-8 mL/day, and when only 10% ethanol solution was available, intake was transiently increased. The results demonstrated that thirst for water caused by i.c.v. infusion of angiotensin II in C57 mice is similar to that observed in BALB/C mice. Unlike BALB/C mice, however, i.c.v. infusion of angiotensin II stimulated intake of ethanol solution. The failure of angiotensin II to cause a large increase in 4% ethanol solution or a sustained increase in 10% ethanol solution intake does not seem to be caused by an aversion to the taste of ethanol solution, but most likely due to postingestional factors.

Intracerebroventricular infusion of angiotensin II increases water and ethanol intake in rats

The influence of prolonged ingestion of ethanol on stimulation of water or ethanol intake by intracerebroventricular infusion of ANG II was evaluated in rats. Animals were maintained for 5-6 mo with either 10% ethanol solution or water as their only source of fluid. In both groups of rats, infusion of ANG II caused a large increase in water intake (7-fold) and a lesser increase in 10% ethanol intake (2-fold). The effect of ANG II on the volume of ethanol solution ingested, however, was inversely related to the concentration of the ethanol solution. As the concentration of ethanol solution was decreased, frequency and duration of drinking bouts increased. The intake of sweetened 10% ethanol solution or commercially produced wine during infusion of ANG II was similar to the intake of 10% ethanol and not related to taste preference. In conclusion, chronic consumption of ethanol solution did not appear to adversely effect ANG II stimulation of water intake. The intake of ethanol solution during infusion of ANG II was inhibited by a direct effect of ingested ethanol and/or by indirect effect from metabolized ethanol.

Histaminergic activation of endogenous angiotensin II fails to inhibit alcohol intake in rats

Demonstrations that alcohol intake can be inhibited by pharmacological activation of the renal renin-angiotensin system (RRA) or injection of angiotensin II (ANG II) in rats led to this study of a role for endogenous ANG II in inhibition of alcohol intake in rats. Relatively small doses of histamine, above threshold for eliciting drinking of water and activation of the RRA, were injected SC in adult male Sprague-Dawley rats with access to 3.0% alcohol in 45-min one-bottle alcohol tests and in two-bottle tests in which alcohol and water were available at the midpoint of the 12-h dark phase. The 0.312 and 1.25 mg/kg doses of SC histamine elevated plasma renin activity to levels similar to those in rats that had just eaten food. Neither dose of histamine affected alcohol intake in one-bottle tests. A relatively large 10 mg/kg dose of histamine increased alcohol intake in a one-bottle test, but decreased alcohol intake and increased water intake in two-bottle tests. The inhibitory effect of the 10 mg/kg dose of histamine on alcohol intake was completely blocked by SC 10 mg/kg losartan, a selective AT1 angiotensin receptor antagonist. This 10 mg/kg dose of losartan given alone, however, failed to increase alcohol intake in one- or two-bottle tests. These results generally do not support a role for endogenous ANG II as an inhibitory physiological signal in the control of alcohol ingestion in rats, because histaminergic activation of RRA, using small but physiologically meaningful doses of histamine, failed to inhibit alcohol intake.

Angiotensin II reduces alcohol intake and choice in water- or food-restricted rats

Two experiments were conducted to assess the effects of administration of the neuropeptide and hormone angiotensin II (AII) on ethanol intake and choice. First, 18 male Wistar rats were water deprived for 23 h and given access to 5% w/v ethanol for 30 min, followed by 30 min of access to water; food was ad lib. Following adaptation to this schedule, rats were randomly assigned to receive an IP injection of 0, 100, or 200 micrograms/kg of AII at either -30 or 0 min prior to ethanol access. Each AII injection decreased ethanol intake only if injected immediately before access; water and food intake were unaffected. Secondly, rats were given food daily at 2% of body weight with ad lib water and randomly assigned to receive either only water or 4% w/v ethanol ad lib on alternate days. Following adaptation, rats were randomly assigned to receive IP saline or 200 micrograms/kg of AII prior to presentation of a choice of ethanol or water for 1 h. AII reduced ethanol intake and increased water intake at 0-30 min after injection. Results confirm previous reports of inhibition of alcohol consumption by peripheral AII, and indicate a temporal constraint on AII's effect, which is consistent with a role as a short-term satiety factor.

The reduction in alcohol intake produced by enalapril is not attenuated by centrally administered angiotensin inhibitors

Angiotensin-converting enzyme (ACE) inhibitors, which prevent the conversion of angiotensin I to angiotensin II, reduce alcohol intake when injected peripherally. The mechanism by which ACE inhibitors produce this effect on alcohol intake is unknown. A rise in the biosynthesis of angiotensin II in the periphery is known to reduce alcohol intake. In this experiment, we examine the possibility that the reduction in alcohol intake produced by an ACE inhibitor, enalapril, is mediated by a rise in angiotensin II in the brain. Enalapril, 20 mg/kg, injected intraperitoneally, produced a 40% reduction in alcohol intake. This reduction was not attenuated by the concurrent administration into the lateral ventricle of either the ACE inhibitors captopril or ceranapril (1, 10, or 25 micrograms), or the angiotensin II receptor antagonist Sar1-Thr8-Angiotensin II (5 micrograms). These findings suggest that the ACE inhibitors do not reduce alcohol intake by raising angiotensin II in the brain.