Angiotensin converting enzyme inhibitors reduce alcohol consumption: some possible mechanisms and important conditions for its therapeutic use

DeepBiomarker2: Prediction of Alcohol and Substance Use Disorder Risk in Post-Traumatic Stress Disorder Patients Using Electronic Medical Records and Multiple Social Determinants of Health

Prediction of high-risk events amongst patients with mental disorders is critical for personalized interventions. We developed DeepBiomarker2 by leveraging deep learning and natural language processing to analyze lab tests, medication use, diagnosis, social determinants of health (SDoH) parameters, and psychotherapy for outcome prediction. To increase the model's interpretability, we further refined our contribution analysis to identify key features by scaling with a factor from a reference feature. We applied DeepBiomarker2 to analyze the EMR data of 38,807 patients from the University of Pittsburgh Medical Center diagnosed with post-traumatic stress disorder (PTSD) to determine their risk of developing alcohol and substance use disorder (ASUD). DeepBiomarker2 predicted whether a PTSD patient would have a diagnosis of ASUD within the following 3 months with an average c-statistic (receiver operating characteristic AUC) of 0.93 and average F1 score, precision, and recall of 0.880, 0.895, and 0.866 in the test sets, respectively. Our study found that the medications clindamycin, enalapril, penicillin, valacyclovir, Xarelto/rivaroxaban, moxifloxacin, and atropine and the SDoH parameters access to psychotherapy, living in zip codes with a high normalized vegetative index, Gini index, and low-income segregation may have potential to reduce the risk of ASUDs in PTSD. In conclusion, the integration of SDoH information, coupled with the refined feature contribution analysis, empowers DeepBiomarker2 to accurately predict ASUD risk. Moreover, the model can further identify potential indicators of increased risk along with medications with beneficial effects.

Role of aldosterone and mineralocorticoid receptor (MR) in addiction: A scoping review

Preclinical and human studies suggest a role of aldosterone and mineralocorticoid receptor (MR) in addiction. This scoping review aimed to summarize (1) the relationship between alcohol and other substance use disorders (ASUDs) and dysfunctions of the aldosterone and MR, and (2) how pharmacological manipulations of MR may affect ASUD-related outcomes. Our search in four databases (MEDLINE, Embase, Web of Science, and Cochrane Library) indicated that most studies focused on the relationship between aldosterone, MR, and alcohol (n = 30), with the rest focused on opioids (n = 5), nicotine (n = 9), and other addictive substances (n = 9). Despite some inconsistencies, the overall results suggest peripheral and central dysregulations of aldosterone and MR in several species and that these dysregulations depended on the pattern of drug exposure and genetic factors. We conclude that MR antagonism may be a promising target in ASUD, yet future studies are warranted.

The effect of telmisartan, an angiotensin receptor blocker, on alcohol consumption and alcohol-induced dopamine release in the nucleus accumbens

Alcohol use disorder remains a major health problem. The mesocorticolimbic dopaminergic system, including the nucleus accumbens region and multiple neural circuits, is involved in its complex underlying mechanism. For instance, alcohol intake stimulates the central and peripheral renin-angiotensin system and increases angiotensin II levels, which predominantly affect angiotensin 1 receptors both in the periphery and in the brain. In this study, we aimed to investigate the effects of the intracerebroventricularly-administered angiotensin 1 receptor blocker telmisartan on the alcohol consumption of male Sardinian alcohol-preferring (sP) rats and on the alcohol-induced dopamine levels in the nucleus accumbens region in Wistar rats. Acute intracerebroventricular administration of telmisartan (100 nM) reduced the alcohol intake for 24 hours without affecting food and water consumption in sP rats. Acute intracerebroventricular injection of the opioid receptor antagonist naloxone (75 nM), tested as a reference compound, also reduced the alcohol consumption in sP rats; however, naloxone's effect lasted only for 30 minutes. In microdialysis experiments, telmisartan administered intracerebroventricularly did not change dopamine levels in the nucleus accumbens that had been induced by acute intraperitoneal alcohol administration in Wistar rats. According to these results, further studies are needed to elucidate the role of the renin-angiotensin system on alcohol use disorder pathophysiology.

Pharmacological treatments for methamphetamine addiction: current status and future directions

INTRODUCTION

Methamphetamine (MA) abuse remains a global health challenge despite intense research interest in the development of pharmacological treatments. This review provides a summary of clinical trials and human studies on the pharmacotherapy of methamphetamine use disorder (MUD). Areas covered: We summarize published clinical trials that tested candidate medications for MUD and also conducted PubMed and Google Scholar searches to identify recently completed clinical trials using the keywords 'methamphetamine' 'addiction' 'pharmacotherapy' and 'clinical trial.' To determine the status of ongoing clinical trials targeting MUD, we also searched the ClinicalTrials.gov online database. We conclude this review with a discussion of current research gaps and future directions. Expert commentary: Clinical trials examining the potential for pharmacotherapies of MUD have largely been negative. Future studies need to address several limitations to reduce the possibility of Type II errors: small sample sizes, high dropout rates or multiple comorbidities. Additionally, new treatment targets, such as MA-induced disruptions in cognition and in the neuroimmune system, merit trials with agents that selectively modulate these processes.

Subjective and Cardiovascular Effects of Intravenous Methamphetamine during Perindopril Maintenance: A Randomized, Double-Blind, Placebo-Controlled Human Laboratory Study

BACKGROUND

Our pilot study suggested that the angiotensin-converting enzyme inhibitor perindopril might reduce some subjective effects produced by i.v. methamphetamine. We characterized the impact of a wider range of perindopril doses on methamphetamine-induced effects in a larger group of non-treatment-seeking, methamphetamine-using volunteers.

METHODS

Before treatment, participants received 30mg methamphetamine. After 5 to 7 days of perindopril treatment (0, 4, 8, or 16mg/d), participants received 15 and 30mg of methamphetamine on alternate days. Before and after treatment, participants rated subjective effects and cardiovascular measures were collected.

RESULTS

Prior to treatment with perindopril, there were no significant differences between treatment groups on maximum or peak subjective ratings or on peak cardiovascular effects. Following perindopril treatment, there were significant main effects of treatment on peak subjective ratings of "anxious" and "stimulated"; compared to placebo treatment, treatment with 8mg perindopril significantly reduced peak ratings of both anxious (P=.0009) and stimulated (P=.0070). There were no significant posttreatment differences between groups on peak cardiovascular effects.

CONCLUSIONS

Moderate doses of perindopril (8mg) significantly reduced peak subjective ratings of anxious and stimulated as well as attenuated many other subjective effects produced by methamphetamine, likely by inhibiting angiotensin II synthesis. Angiotensin II is known to facilitate the effects of norepinephrine, which contributes to methamphetamine's subjective effects. The lack of a classic dose-response function likely results from either nonspecific effects of perindopril or from between-group differences that were not accounted for in the current study (i.e., genetic variations and/or caffeine use). The current findings suggest that while angiotensin-converting enzyme inhibitors can reduce some effects produced by methamphetamine, more consistent treatment effects might be achieved by targeting components of the renin-angiotensin system that are downstream of angiotensin-converting enzyme.

The angiotensin-converting enzyme inhibitor perindopril treatment alters cardiovascular and subjective effects of methamphetamine in humans

A variety of medications have been assessed for their potential efficacy for the treatment of methamphetamine dependence. We conducted this study in an attempt to evaluate the potential of a novel class of medications, angiotensin-converting enzyme inhibitors, as treatments for methamphetamine dependence. All participants met the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, third revision (DSM-IV-TR) criteria for methamphetamine abuse or dependence and were not seeking treatment at the time of study entry. The study was conducted using a double-blind design. Subjects received a baseline series of intravenous (IV) doses of methamphetamine (15 mg and 30 mg) and placebo. Subjects received a second identical series of methamphetamine doses 3 and 5 days after initiation of once-daily oral placebo or perindopril treatment. The dose of perindopril was 2 mg, 4mg, or 8 mg administered in the morning. Perindopril treatment was tolerated well. There were no main effects of perindopril on methamphetamine-induced changes in cardiovascular or subjective effects. There were significant perindoprilmethamphetamine interactions for diastolic blood pressure and for ratings of "Any Drug Effect", indicating inverted U dose-effect functions for these indices.

Plasticity and impact of the central renin–angiotensin system during development of ethanol dependence

Pharmacological and genetic interference with the renin-angiotensin system (RAS) seems to alter voluntary ethanol consumption. However, understanding the influence of the RAS on ethanol dependence and its treatment requires modeling the neuroadaptations that occur with prolonged exposure to ethanol. Increased ethanol consumption was induced in rats through repeated cycles of intoxication and withdrawal. Expression of angiotensinogen, angiotensin-converting enzyme, and the angiotensin II receptor, AT1a, was examined by quantitative reverse transcription polymerase chain reaction. Increased ethanol consumption after a history of dependence was associated with increased angiotensinogen expression in medial prefrontal cortex but not in nucleus accumbens or amygdala. Increased angiotensinogen expression also demonstrates that the astroglia is an integral part of the plasticity underlying the development of dependence. The effects of low central RAS activity on increased ethanol consumption were investigated using either spirapril, a blood-brain barrier-penetrating inhibitor of angiotensin-converting enzyme, or transgenic rats (TGR(ASrAOGEN)680) with reduced central angiotensinogen expression. Spirapril reduced ethanol intake in dependent rats compared to controls. After induction of dependence, TGR(ASrAOGEN)680 rats had increased ethanol consumption but to a lesser degree than Wistar rats with the same history of dependence. These data suggest that the central RAS is sensitized in its modulatory control of ethanol consumption in the dependent state, but pharmacological or genetic blockade of the system appears to be insufficient to halt the progression of dependence.

Central Overexpression of Angiotensin AT1AReceptors Prevents Dopamine D2Receptor Regulation of Alcohol Consumption in Mice

BACKGROUND

While angiotensin receptors are found on the soma and terminals of dopaminergic neurons, controversy surrounds the potential role of angiotensin in alcohol consumption.

METHODS

Using a transgenic mouse with a brain-specific overexpression of angiotensin AT(1A) receptors (NSE-AT(1A) mice), we have examined the role of angiotensin in alcohol consumption and alcohol-induced regulation of the dopaminergic system.

RESULTS

The functional relevance of the overexpressed AT(1A) receptors was confirmed by an exaggerated rehydration response following 24-hour dehydration. NSE-AT(1A) mice showed a high preference for alcohol (similar to wild-type mice); yet, raclopride treatment had no effect on alcohol consumption in NSE-AT(1A) mice, while significantly reducing consumption in wild-type mice. In contrast, NSE-AT(1A) mice showed enhanced sensitivity to raclopride compared with wild types in terms of D(2) receptor up-regulation within the ventral mesencephalon. In addition, striatal D(2) receptors in NSE-AT(1A) mice were sensitive to up-regulation by chronic alcohol consumption.

CONCLUSIONS

Collectively, these data imply that while expression of angiotensin AT(1A) receptors on striatal neurons has no impact upon basal alcohol consumption or preference, AT(1A) receptors do modulate the sensitivity of dopamine D(2) receptors to regulation by alcohol and the ability of a D(2) receptor antagonist to reduce consumption.

The effects of polymorphisms in genes from the renin-angiotensin, bradykinin, and fibrinolytic systems on plasma t-PA and PAI-1 levels are dependent on environmental context

Thrombosis is a key factor in the pathophysiology of cardiovascular disease. Important biochemical constituents of the fibrinolytic system, affecting thrombosis, include tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1). Both t-PA and PAI-1 are determined by multiple genetic and environmental factors. We aimed to investigate whether the effects of polymorphism in genes from the renin-angiotensin, bradykinin, and fibrinolytic systems on t-PA or PAI-1 levels are dependent on environmental factors in a large population-based sample from the PREVEND study in Groningen, The Netherlands (n = 2,527). We found strong evidence (P <or= 0.02) for interaction effects of polymorphisms from the bradykinin receptor (BDKRB2) gene and alcohol consumption on t-PA in females and males and on PAI-1 in males. Only suggestive evidence (P <or= 0.10) was present for an interaction effect of the BDKRB2 gene and alcohol consumption on PAI-1 levels in females. Another consistent finding was evidence for an interaction between bradykinin receptor (BDKRB2) gene polymorphisms and body size as measured by body mass index and/or waist-hip-ratio. For each gender and for both t-PA and PAI-1 there was at least one BDKRB2-body size combination that exhibited suggestive (P <or= 0.10), significant (P <or= 0.04) and/or strong evidence (P <or= 0.02) for interaction. In conclusion, the genetic architecture of t-PA and PAI-1 is dependent on the environmental context such as body size and alcohol use. The present study emphasizes the importance of including environmental factors in genetic analyses to fully comprehend the genetic architecture of a specific trait.

Candidate genes, pathways and mechanisms for alcoholism: an expanded convergent functional genomics approach

We describe a comprehensive translational approach for identifying candidate genes for alcoholism. The approach relies on the cross-matching of animal model brain gene expression data with human genetic linkage data, as well as human tissue data and biological roles data, an approach termed convergent functional genomics. An analysis of three animal model paradigms, based on inbred alcohol-preferring (iP) and alcohol-non-preferring (iNP) rats, and their response to treatments with alcohol, was used. A comprehensive analysis of microarray gene expression data from five key brain regions (frontal cortex, amygdala, caudate-putamen, nucleus accumbens and hippocampus) was carried out. The Bayesian-like integration of multiple independent lines of evidence, each by itself lacking sufficient discriminatory power, led to the identification of high probability candidate genes, pathways and mechanisms for alcoholism. These data reveal that alcohol has pleiotropic effects on multiple systems, which may explain the diverse neuropsychiatric and medical pathology in alcoholism. Some of the pathways identified suggest avenues for pharmacotherapy of alcoholism with existing agents, such as angiotensin-converting enzyme (ACE) inhibitors. Experiments we carried out in alcohol-preferring rats with an ACE inhibitor show a marked modulation of alcohol intake. Other pathways are new potential targets for drug development. The emergent overall picture is that physical and physiological robustness may permit alcohol-preferring individuals to withstand the aversive effects of alcohol. In conjunction with a higher reactivity to its rewarding effects, they may able to ingest enough of this nonspecific drug for a strong hedonic and addictive effect to occur.

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.

Gene expression and activity of specific opioid-degrading enzymes in different brain regions of the AA and ANA lines of rats

There is increasing evidence that alcoholism runs in families suggesting that genetic factors may play a role. In support of this hypothesis, the alcohol-preferring (AA) and the alcohol-avoiding (ANA) rat lines have been developed through selective outbreeding. Numerous studies indicate that the endogenous opioid system may be involved in controlling ethanol consumption. Changes in opioid peptides and opioid receptors have been described after ethanol intake. But, the influence of ethanol on peptidolytic degradation of opioid peptides has been largely ignored, although the peptidase-mediated metabolism of neuropeptides is known as an important regulatory site of peptidergic transmission. Neutral endopeptidase 24.11 (NEP) and angiotensin-converting enzyme (ACE) degrade neuropeptides, including enkephalin and are expressed in the brain. Furthermore, a good correspondence between the regional distribution of NEP and opioid receptors in rat brain has already been reported pointing to a possible role of NEP in regulating opioid peptides. For both enzymes studied, the gene expression pattern was found to be in good agreement with the corresponding enzyme activities in the brain regions investigated, showing the highest levels for both specific mRNAs and enzyme activities in the striatum. Differences in both measured parameters were detected in distinct brain regions of AA and ANA rats. Furthermore, in some brain regions discrepancies between ACE and NEP mRNA levels and the corresponding enzyme activities were observed. For example, in olfactory bulb and striatum such discrepancies were found for both enzymes studied. In tegmentum/colliculi a higher NEP gene expression in AA rats was associated with a higher NEP enzyme activity compared to the amounts found in ANA rats.

Effect of captopril on voluntary consumption of ethanol, water and solid food by UChA and UChB rats

Angiotensin converting enzyme inhibitors (ACEI) have been reported to reduce ethanol consumption in rats, but it is unclear whether this effect is specific for ethanol or secondary to effects on appetite or satiation for calories or water. In the present study we assessed the effect of captopril, an ACEI, on the voluntary consumption of 10% ethanol solution, water and solid food in our strain of rats genetically selected for their voluntary consumption of ethanol, namely UChA (low consumer) and UChB (high consumer). Captopril (30 mg/kg) was injected intraperitoneally for 3 consecutive days to UChA and UChB rats and ethanol, water and food intake were measured before, during and after captopril treatment; these results were compared with those produced by a control saline solution. Results showed that captopril produced a significant reduction of alcohol voluntary consumption in UChB but not in UChA rats. However, this effect was not specific for ethanol since captopril also induced a significant decrease in food intake leading to a loss of weight in both rat strains, suggesting that it seems to be secondary to changes in appetite for calories.

Acetaldehyde inhibits serum aminopeptidases

Aminopeptidase A (APA)- and aminopeptidase M (APM)-like activity were assayed in Moni-Trol ES with L-alpha-aspartyl-beta-naphthylamide and L-alanyl-beta-naphthylamide, respectively. Upon preincubation of the serum with 89.4, 223.5, and 447 mM acetaldehyde at room temperature for 30 min, a reduction in 26.8%, 55.3%, and 75.8% aminopeptidase A activity was observed. Similarly, aminopeptidase M activity was reduced by 26.5% and 53.1% upon preincubation with 223.5 and 447 mM acetaldehyde. Ethanol at 84.9, 212.3, and 427.9 mM did not significantly affect the enzymic activity. Because aminopeptidase A and aminopeptidase M also degrade the pressor substance, angiotensin II, it is suggested that inhibition of aminopeptidase A- and aminopeptidase M-like activity by acetaldehyde, the product of ethanol metabolism, may lead to higher levels of circulating angiotensin II and, consequently, hypertension, in alcoholics. The hydrolysis of lysine-p-nitroanilide, an aminopeptidase B substrate, was also inhibited upon addition of acetaldehyde to Moni-Trol ES serum.

New drugs for the treatment of experimental alcoholism

This article presents a current overview of the efforts to suppress pharmacologically the craving, dependence, or other factors associated with the self-selection of alcohol in an experimental animal. The contemporary status of the pharmacotherapy of experimental alcoholism similarly is described for different animal models of alcohol drinking. An evaluation is presented of several classes of drug for their efficacy in ameliorating the volitional ingestion of alcohol in the presence of an alternative fluid. Currently, two main experimental animal models of alcoholism are being used in this endeavor: (a) genetic lines or substrains of high alcohol preferring or high drinking rats; and (b) strains of nondrinking or low alcohol preferring rats which are induced chemically to prefer alcohol. Because of technical, methodological, and other issues surrounding the procedures used to assess the efficacy of a drug in reducing alcohol intake, several of the newer findings remain controversial. For example, serious side effects on the intake of food, caloric regulation, motor activity, or other functions would preclude the clinical utility of the drug. However, several drugs which affect monoaminergic neurons as well as opioid systems in the brain now seem to offer promise as agents which do possess clinical benefits. Two of these drugs, FG5606 (amperozide) and FG 5893 are essentially "antialcoholic" or anticraving and are without any significant side effects on cerebral mechanisms responsible for hunger, caloric intake, motor activity, or other physiological process. Amperozide, a 5-HT2 receptor antagonist with dopamine releasing properties, is particularly notable because of its irreversible nature in attenuating alcohol preference for months after its administration. It is concluded that future pharmacological research on presently available and newly developed compounds will provide exciting opportunities to the clinician who can utilize a particular drug as an adjunctive tool in the therapeutic treatment of the alcoholic individual.

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.

Brain angiotensin receptor subtypes in the control of physiological and behavioral responses

This review summarizes emerging evidence that supports the notion of a separate brain renin-angiotensin system (RAS) complete with the necessary precursors and enzymes for the formation and degradation of biologically active forms of angiotensins, and several binding subtypes that may mediate their diverse functions. Of these subtypes the most is known about the AT1 site which preferentially binds angiotensin II (AII) and angiotensin III (AIII). The AT1 site appears to mediate the classic angiotensin responses concerned with body water balance and the maintenance of blood pressure. Less is known about the AT2 site which also binds AII and AIII and may play a role in vascular growth. Recently, an AT3 site was discovered in cultured neoblastoma cells, and an AT4 site which preferentially binds AII(3-8), a fragment of AII now referred to as angiotensin IV (AIV). The AT4 site has been implicated in memory acquisition and retrieval, and the regulation of blood flow. In addition to the more well-studied functions of the brain RAS, we review additional less well investigated responses including regulation of cellular function, the modulation of sensory and motor systems, long term potentiation, and stress related mechanisms. Although the receptor subtypes responsible for mediating these physiologies and behaviors have not been definitively identified research efforts are ongoing. We also suggest potential contributions by the RAS to clinically relevant syndromes such as dysfunctions in the regulation of blood flow and ischemia, changes in cognitive affect and memory in clinical depressed and Alzheimer's patients, and angiotensin's contribution to alcohol consumption.

Bradykinin suppresses alcohol intake and plays a role in the suppression produced by an ACE inhibitor

The possible role of the endogenous kinins in the control of alcohol intake was assessed in two experiments. In Experiment 1, naive rats, maintained on ad lib food and water, were given daily 40-min access to a 6% (w/v) alcohol solution and water. Daily intraperitoneal (IP) injections of captopril (20 mg/kg) significantly reduced alcohol intake, while pretreatment with subcutaneous (SC) injections of the bradykinin antagonist [D-Phe7]-bradykinin (100-300 micrograms/kg) attenuated the suppressive effect of captopril on alcohol intake. The saline vehicle or the bradykinin antagonist alone did not alter alcohol intake. In Experiment 2, bradykinin was administered daily at 100, 200, and 400 micrograms/kg doses SC either alone or in combination with captopril 10 mg/kg IP. Neither bradykinin nor captopril by themselves changed alcohol or water intake. Bradykinin combined with captopril stimulated water intake and reduced alcohol intake by up to 70%. This effect was not due to drug-induced changes in the pharmacokinetics of alcohol. The angiotensin II receptor antagonist [Sar1,Thr8]-angiotensin II at 250 and 500 micrograms/kg SC attenuated the stimulation of water intake but not the reduction in alcohol intake. It is suggested that by inhibiting kininase II, ACE inhibitors extend the duration of action of bradykinin and thereby unmask a potent inhibition of alcohol intake mediated by kinins--an effect that is dissociable from the accompanying stimulation of water intake. Taken together, these results point to an involvement of the kinin system in the regulation of alcohol intake and in particular to a role of bradykinin in the suppressive effect of ACE inhibitors on alcohol intake.

Captopril and hydrochlorothiazide (Capozide) combine to enhance the reduction in voluntary alcohol intake in rats

The effect of Capozide, the combination of captopril with a hydrochlorothiazide diuretic, on voluntary alcohol intake was assessed in two experiments. In experiment 1 naive rats who were maintained on ad libitum food and water were given daily 40-min access to a 6% (w/v) alcohol solution and water. Daily intraperitoneal injections of captopril (10 mg/kg) reduced alcohol intake, but the combination of captopril (5 and 10 mg/kg) and hydrochlorothiazide (2.5, 5, and 10 mg/kg) enhanced the reduction in intake. In experiment 2, captopril alone, hydrochlorothiazide alone, and the combination of captopril and hydrochlorothiazide were again administered daily in the limited access procedure. Captopril (10 mg/kg) again reduced alcohol intake as did all three doses of hydrochlorothiazide (2.5, 5, and 10 mg/kg). Compared with the individual effects of captopril and hydrochlorothiazide, Capozide exerted a supra-additive reduction in alcohol intake. These effects were not due to drug-induced changes in the pharmacokinetics of alcohol. Taken together these results demonstrate an enhanced potency of Capozide in suppressing alcohol intake and invite their testing in a population of hypertensive alcoholics and alcohol abusers.

Angiotensin and captopril increase alcohol intake

Reportedly both angiotensin II (ANG II) and angiotensin-converting enzyme (ACE) inhibitors reduce ethanol intake when they are injected SC into certain chronic experimental conditions in the rat. The ACE inhibitors are suggested to reduce ethanol intake by increasing ANG II synthesis in the brain. The present results show that several different methods can produce opposite effects of ANG II and the ACE inhibitor captopril on ethanol intake. Continuous intraventricular infusions of ANG II for 7 days or low doses of oral or SC-infused captopril for up to 12 days increased the intake of ethanol. The only reduction of ethanol intake resulted from a universal blockade of all ACE in both the brain and periphery, a condition in which ANG II could not possibly mediate the decrease. The results contradict the hypothesis that ethanol intake is suppressed by centrally acting or centrally synthesized ANG II. ACE inhibitors may reduce ethanol intake only when they affect the brain as well as the periphery.

Mnemogenic effects of injecting RA-octil, a CE-inhibitor derivate, systemically or into the basal forebrain

The aim of this study was to investigate the effects of systemically or intracerebrally administered RA-octil, a derivative of the angiotensin converting enzyme (CE)-inhibitor ramipril, on memory and reinforcement and to compare its effectiveness with that of the neurokinin substance P (SP). In the first experiment systemic post-trial application of RA-octil and SP in the rat enhanced habituation, a learning task which does not require motivational treatments. Unlike SP, injection of RA-octil did not have reinforcing effects as measured with a conditioned place preference task. In the second experiment, a facilitation of inhibitory avoidance learning was obtained by injection of RA-octil or SP unilaterally into the basal forebrain immediately after the learning trial. In contrast, a 5 h delayed injection of RA-octil had no effects on learning. The results demonstrate memory-enhancing effects of RA-octil after systemic application as well as after injection into the basal forebrain. Furthermore, the mnemogenic effects of SP after central and peripheral administration were confirmed. Since RA-octil, although being structurally closely related to CE-inhibitors, does not affect plasma CE, yet exhibits mnemogenic effects, it is possible that "cognition-enhancing" actions of CE-inhibitors are dissociable from their action within the renin-angiotensin system.

Reducing the desire to drink. Pharmacology and neurobiology

The past decade has witnessed major advances in understanding of neural functioning and neurobiological bases of alcohol consumption. Concurrent with this, a range of exciting investigations have been conducted on pharmacologic agents that may curb drinking behavior. Research is reviewed on several promising medications influencing neurotransmitter and endocrine systems with particular attention to the serotonergic and opioid systems. Following this overview, recommendations are offered regarding research methodology to support future pharmacotherapy trials.

Effects of angiotensin II and an angiotensin converting enzyme inhibitor on alcohol intake in P and NP rats

While it is known that randomly bred normotensive Wistar stock and hypertensive rats alter their alcohol consumption when activity in the renin-angiotensin (R-A) system is modified, the effect of manipulations to the R-A system on alcohol intake in genetically selected alcohol-preferring P and -nonpreferring NP rats has not been assessed. In Experiment 1, nine P rats and 8 NP rats were injected with the saline vehicle and offered limited access to 10% (v/v) alcohol for 40 min each day for 7 days. When intake stabilized both groups were given daily intraperitoneal injections of the angiotensin converting enzyme inhibitor, ceranapril (20 mg/kg) 45 min prior to alcohol access for 11 days. Ceranapril (SQ 29,852) reduced alcohol intake in both the P and NP animals, while saline had no effect. In Experiment 2, these same two groups of P and NP rats were injected with three doses of angiotensin II (ANG II) (100, 200, 400 micrograms/kg) immediately prior to alcohol access. Each dose was tested for 10 consecutive days, with a 14-day period of no drug preceding and following the ANG II treatments. ANG II reduced alcohol intake in the NP rats and produced a dose-dependent reduction in the alcohol consumption of the P rats. These findings indicate that the renin-angiotensin system can modify alcohol consumption in rats selectively bred for high and low alcohol intake.

Manipulations of the renin-angiotensin system and intake of a sweetened alcoholic beverage among rats

Standard laboratory rats were maintained on a daily regimen involving deprivation of fluids for 22 h followed by a 2-h opportunity to drink water and a sweetened alcoholic beverage. Angiotensin II, in doses ranging from 0.1 to 1.25 mg/kg, dose relatedly decreased rats' mean intake of ethanol. All doses increased rats' mean intake of water. Angiotensin II, 0.25 mg/kg, reliably reduced intake of ethanol when it was presented alone during the 1st h of the daily 2-h drinking session, and reliably increased intake of water when it was subsequently presented alone during the 2nd h. Thus the reduction in intake of ethanol seen when the alcoholic beverage is presented concurrently with water is probably not merely due to the increase in intake of water. Lisinopril, an angiotensin converting enzyme inhibitor, in doses of 0.3, 1.0, and 3.0 mg/kg, dose relatedly decreased intake of ethanol, but only after several days of injections. Concurrent intake of water was increased dose relatedly. When injections of lisinopril ceased, intakes of both ethanol and water took several days to return to control levels. Pretreatment with lisinopril, 3.0 mg/kg, for 8 days, had no effect on subsequent intakes of either water or ethanol. Lisinopril, 3.0 mg/kg, had no effect on rats' intake of a sweet solution without ethanol. These results confirm previous work and extend the data base supporting the idea that the renin-angiotensin system plays a role in modulating intake of ethanol.

The amino acid composition of angiotensin alters its ability to reduce alcohol consumption in rats

The voluntary consumption of alcohol has been shown to be reduced by a variety of manipulations which enhance activity in the renin-angiotensin system, including the administration of the bovine form of angiotensin II-[Val5]-ANG II. The present study investigated the relationship between the amino acid composition of angiotensin II and its ability to reduce alcohol intake by administering a number of different forms or fragments of the parent peptide. [Ile5]-Angiotensin II ([Ile5]-ANG II), two endogenous fragments of angiotensin II [( Des-Asp1]-ANG II and [Des-Phe8]-ANG II) were administered subcutaneously in rats across a range of doses. [Ile5]-ANG II reduced alcohol intake at all doses tested between 20 and 400 micrograms/kg while [Des-Asp1]-ANG II reduced alcohol intake only at the 400 micrograms/kg dose. [Des-Phe8]-ANG II had no effect on alcohol intake at any dose tested. Administration of the antagonist [Sar1-Thr8]-ANG II by itself did not enhance alcohol intake. While the pressor and dipsogenic properties of these fragments sometimes correlated with the reduction in alcohol intake they were not a causal factor in decreasing the intake. These results indicate that variations in the peptide composition of angiotensin can significantly alter its ability to reduce the consumption of alcohol.

Pharmacotherapies for alcoholism: promising agents and clinical issues

The past 10 years have witnessed important advances in research on pharmacotherapy for alcoholism. Promising drugs are discussed under six headings: agents to treat alcohol withdrawal; anticraving agents; agents that make drinking an aversive experience; agents to alleviate concomitant psychiatric problems; agents to treat concurrent drug abuse; and amethystic ("sobering-up") agents. Research on the drug classes is summarized and clinical issues surrounding specific agents and alcoholism pharmacotherapy in general are discussed. Finally, long-range therapeutic implications of recent findings on the actions of alcohol on basic mechanisms of the brain are offered.

Regulation of alcohol consumption by the renin-angiotensin system: a review of recent findings and a possible mechanism of action

The renin-angiotensin system has traditionally been associated with the regulation of fluid and electrolyte balance. In this review we summarize the data which ascribes a completely new function to this system, i.e., the regulation of alcohol consumption. In addition, we suggest a possible mechanism for this effect based on the concept of a satiety or stop process. The approach taken was to examine the effect on alcohol intake of a wide variety of drug, genetic, dietary, surgical and neurosurgical manipulations, each of which has a range of biological effects characteristic of that manipulation, but all of which share the common property of altering activity in the renin-angiotensin system. The effect of these manipulations on alcohol intake was most parsimoniously explained by reference to their ability to raise or lower activity in the renin-angiotensin system. Any intervention which modulates activity in this system, either directly or indirectly, is likely to have consequences for alcohol consumption.

Effects of the novel compound Hoe 065, a central enhancer of cholinergic activity, on voluntary alcohol consumption in rats

Hoe 065 is a compound structurally related to the angiotensin converting enzyme inhibitors and capable of increasing central cholinergic activity. The effects of this compound were studied on alcohol intake and on the reduction in alcohol intake produced by abutapril, an angiotensin converting enzyme inhibitor. Hoe 065 failed to alter alcohol intake or to modify the reduction in alcohol intake produced by abutapril. These findings suggest that enhanced cholinergic activity may not play a role in the control of alcohol consumption and may not be part of the mechanism by which the angiotensin converting enzyme inhibitors reduce alcohol intake.