Administration Of Acetaldehyde Research Articles

Acetaldehyde via CGRP receptor and TRPA1 in Schwann cells mediates ethanol-evoked periorbital mechanical allodynia in mice: relevance for migraine

BackgroundIngestion of alcoholic beverages is a known trigger of migraine attacks. However, whether and how ethanol exerts its pro-migraine action remains poorly known. Ethanol stimulates the transient receptor potential vanilloid 1 (TRPV1) channel, and its dehydrogenized metabolite, acetaldehyde, is a known TRP ankyrin 1 (TRPA1) agonist.MethodsPeriorbital mechanical allodynia following systemic ethanol and acetaldehyde was investigated in mice after TRPA1 and TRPV1 pharmacological antagonism and global genetic deletion. Mice with selective silencing of the receptor activated modifying protein 1 (RAMP1), a component of the calcitonin gene-related peptide (CGRP) receptor, in Schwann cells or TRPA1 in dorsal root ganglion (DRG) neurons or Schwann cells, were used after systemic ethanol and acetaldehyde.ResultsWe show in mice that intragastric ethanol administration evokes a sustained periorbital mechanical allodynia that is attenuated by systemic or local alcohol dehydrogenase inhibition, and TRPA1, but not TRPV1, global deletion, thus indicating the implication of acetaldehyde. Systemic (intraperitoneal) acetaldehyde administration also evokes periorbital mechanical allodynia. Importantly, periorbital mechanical allodynia by both ethanol and acetaldehyde is abrogated by pretreatment with the CGRP receptor antagonist, olcegepant, and a selective silencing of RAMP1 in Schwann cells. Periorbital mechanical allodynia by ethanol and acetaldehyde is also attenuated by cyclic AMP, protein kinase A, and nitric oxide inhibition and pretreatment with an antioxidant. Moreover, selective genetic silencing of TRPA1 in Schwann cells or DRG neurons attenuated periorbital mechanical allodynia by ethanol or acetaldehyde.ConclusionsResults suggest that, in mice, periorbital mechanical allodynia, a response that mimics cutaneous allodynia reported during migraine attacks, is elicited by ethanol via the systemic production of acetaldehyde that, by releasing CGRP, engages the CGRP receptor in Schwann cells. The ensuing cascade of intracellular events results in a Schwann cell TRPA1-dependent oxidative stress generation that eventually targets neuronal TRPA1 to signal allodynia from the periorbital area.

Role of Acetaldehyde in Ethanol Reversal of Tolerance to Morphine-Induced Respiratory Depression in Mice.

BackgroundOpioid users regularly consume other drugs such as alcohol (ethanol). Acute administration of ethanol rapidly reverses tolerance to morphine-induced respiratory depression. However, recent research has suggested that the primary metabolite of ethanol, acetaldehyde, may play a key role in mediating the CNS effects seen after ethanol consumption. This research investigated the role of acetaldehyde in ethanol reversal of tolerance to morphine-induced respiratory depression.MethodsTolerance was induced in mice by 6-days implantation of a 75 mg morphine pellet with control mice implanted with a placebo pellet. Tolerance was assessed by acute morphine administration on day 6 and respiration measured by plethysmography. Levels of acetaldehyde were inhibited or enhanced by pre-treatments with the acetaldehyde chelator D-penicillamine and the inhibitor of acetaldehyde dehydrogenase disulfiram respectively.ResultsMorphine pellet implanted mice displayed tolerance to an acute dose of morphine compared to placebo pellet implanted controls. Acute acetaldehyde administration dose-dependently reversed tolerance to morphine respiratory depression. As previously demonstrated, ethanol reversed morphine tolerance, and this was inhibited by D-penicillamine pre-treatment. An acute, low dose of ethanol that did not significantly reverse morphine tolerance was able to do so following disulfiram pre-treatment.ConclusionThese data suggest that acetaldehyde, the primary metabolite of ethanol, is responsible for the reversal of morphine tolerance observed following ethanol administration.

High Ethanol and Acetaldehyde Inhibit Glutamatergic Transmission in the Hippocampus of Aldh2-Knockout and C57BL/6N Mice: an In Vivo and Ex Vivo Analysis.

We aimed to investigate whether ethanol (EtOH) and acetaldehyde (AcH) can affect glutamate and its receptors GluN1 and GluA1 in the hippocampus of Aldh2-knockout (Aldh2-KO) and C57BL/6N (wild-type (WT)) mice. To do this, we first examined the effect of local administration of EtOH (100mM, 200mM, and 500mM) and AcH (100μM, 200μM, and 500μM) on extracellular glutamate levels in freely moving mice. Retrodialysis of 200mM and 500mM EtOH into the hippocampus of WT and Aldh2-KO mice produced significant decreases in extracellular glutamate levels (p < 0.05). A dose of 500mM EtOH induced a greater decrease in Aldh2-KO mice (p < 0.05) than in WT mice, indicating the action of AcH. Similarly, perfusion of 200μM and 500μM AcH decreased glutamate in Aldh2-KO mice (p < 0.05), but this decrease was not seen in WT mice at any AcH dose. Second, we tested whether the EtOH- and AcH-induced decrease in glutamate was associated with decreases in GluN1 and GluA1 expression, as measured by real-time PCR and Western blot. We found a significant decrease in GluN1 (p < 0.05) and GluA1 (p < 0.05) subunits after a high dose of EtOH (4.0g/kg) and AcH (200mg/kg) in WT mice. However, a 2.0g/kg dose of EtOH did not produce a consistent decrease in GluN1 or GluA1 between messenger RNA and protein. In Aldh2-KO mice, all three doses of EtOH (1.0g/kg, 2.0g/kg, and 4.0g/kg) and AcH (50mg/kg, 100mg/kg, and 200mg/kg) decreased GluN1 expression (p < 0.05), while moderate-to-high doses of EtOH (2.0g/kg and 4.0g/kg) and AcH (100mg/kg and 200mg/kg) decreased GluA1 expression (p < 0.05). Together, these in vivo and ex vivo data suggest that EtOH and AcH decrease extracellular glutamate in the hippocampus of mice with a concomitant decrease in GluN1 and GluA1 subunits, but these effects require relatively high concentrations and may, therefore, explain the consequences of EtOH intoxication.

Protective effects of N-acetylcysteine and taurine on oxidative stress induced by chronic acetaldehyde administration in rat liver and brain tissues

Aim: Acetaldehyde (AA) is one of the main products of alcohol metabolism. Exposure to AA can occur through ingestion of several dietary products, inhalation of cigarette smoke/automobile exhausts, or contact with cosmetics. AA accumulation causes oxidative stress. The aim of this study was to investigate the prooxidant/antioxidant status in rats chronically exposed to AA, and to evaluate the effects of N-acetylcysteine (NAC) and taurine (TAU) on prooxidant/antioxidant balance. Methods: Sprague Dawley rats were divided in the following groups (n=8; each): Control, AA, AA+NAC, AA+TAU. Reactive oxygen species (ROS), diene conjugate (DC), malondialdehyde (MDA), protein carbonyl (PC), ferric reducing antioxidant power (FRAP) and glutathione (GSH) levels as well as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were determined in liver and brain tissues. Results: AA treatment in drinking water was detected to induce prooxidant state in both liver and brain of rats. NAC treatment decreased AA-induced prooxidant status in both tissues. Although TAU treatment diminished ROS levels, MDA and PC levels remained unchanged in examined tissues of AA-treated rats. NAC and TAU elevated liver and brain GSH levels in AA-treated rats. Conclusion: Chronic AA administration has created a prooxidant condition, and NAC/TAU appears to be useful in suppression of the developed oxidative stress.

Moderate to high ethanol and acetaldehyde administration decreases c-fos protein expression in the hippocampus of Aldh2-knockout and C57BL/6N mice

Background: Ethanol (EtOH) and acetaldehyde (AcH) have long been associated with many adverse effects in the central nervous system. c-fos has been used as an indirect index of neural activity.&#x0D; Method: Here, we investigated the effects of systemic administration of EtOH and AcH on the expression of c-fos protein in the hippocampus of Aldh2-knockout (Aldh2-KO) mice. The animals received an intraperitoneal injection of saline (control), EtOH (1.0, 2.0 and 4.0 g/kg) or AcH (50, 100 and 200 mg/kg), and the expression of c-fos protein was measured by Western blotting.&#x0D; Result: We found that EtOH at doses of 2.0 and 4.0 g/kg decreased c-fos in wild-type (WT) mice, whereas EtOH at all three doses tested (1.0-4.0 g/kg) decreased c-fos in Aldh 2-KO mice. Likewise, AcH at doses of 100 and 200 mg/kg had a significant effect in lowering c-fos protein in both WT and Aldh2-KO mice.&#x0D; Conclusion: Our observations suggest that moderate to high EtOH and AcH can decrease the expression of c-fos protein in the mouse hippocampus. This effect may support, at least in part, the link between c-fos and spatial memory deficits following EtOH and AcH exposure as we have observed in our previous study.&#x0D; Bangladesh Journal of Medical Science Vol.19(1) 2020 p.83-89

Acetaldehyde administration induces salsolinol formation in vivo in the dorsal striatum of Aldh2-knockout and C57BL/6N mice

Acetaldehyde (AcH) and salsolinol play important roles in the central effects of ethanol. This study aimed to investigate the effect of administration of AcH on dopamine (DA), DA-derived salsolinol and serotonin (5-HT) levels in the dorsal striatum of Aldh2-knockout (Aldh2-KO) and C57BL/6 N (WT) mice. Animals were treated with AcH (50, 100 and 200 mg/kg) intraperitoneally and dialysate levels of DA, 5-HT and salsolinol were determined using in vivo microdialysis coupled with HPLC-ECD. Salsolinol was first detected at 20 min after AcH administration, and reached its peak concentration (WT mice: 0.29 ± 0.22 pg/μl; Aldh2-KO mice: 0.63 ± 0.17 pg/μl) at 25 min in the 200 mg/kg AcH group, before decreasing rapidly and reaching zero at approximately 55–80 min. Treatment with 100 and 200 mg/kg AcH increased levels of salsolinol in both WT and Aldh2-KO mice, with 200 mg/kg AcH inducing a higher level of salsolinol in Aldh2-KO mice than in WT mice. Treatment with 50 mg/kg AcH produced a small increase in salsolinol levels in Aldh2-KO mice, whereas no elevation of salsolinol was detected in WT mice. The increase in salsolinol formation was found to occur a dose-dependent manner in both genotypes. Administration of AcH and the subsequent changes in salsolinol concentrations did not change DA or 5-HT levels in either genotype. Our study suggests that AcH dose-dependently increases the formation of salsolinol in the dorsal striatum of mice, which provides further support for the role of AcH in salsolinol formation in the animal brain.

Mitochondrial ROS induced by chronic ethanol exposure promote hyper-activation of the NLRP3 inflammasome

Alcohol use disorders are common both in the United States and globally, and are associated with a variety of co-morbid, inflammation-linked diseases. The pathogenesis of many of these ailments are driven by the activation of the NLRP3 inflammasome, a multi-protein intracellular pattern recognition receptor complex that facilitates the cleavage and secretion of the pro-inflammatory cytokines IL-1β and IL-18. We hypothesized that protracted exposure of leukocytes to ethanol would amplify inflammasome activation, which would help to implicate mechanisms involved in diseases associated with both alcoholism and aberrant NLRP3 inflammasome activation. Here we show that long-term ethanol exposure of human peripheral blood mononuclear cells and a mouse macrophage cell line (J774) amplifies IL-1β secretion following stimulation with NLRP3 agonists, but not with AIM2 or NLRP1b agonists. The augmented NRLP3 activation was mediated by increases in iNOS expression and NO production, in conjunction with increases in mitochondrial membrane depolarization, oxygen consumption rate, and ROS generation in J774 cells chronically exposed to ethanol (CE cells), effects that could be inhibited by the iNOS inhibitor SEITU, the NO scavenger carboxy-PTIO, and the mitochondrial ROS scavenger MitoQ. Chronic ethanol exposure did not alter K+ efflux or Zn2+ homeostasis in CE cells, although it did result in a lower intracellular concentration of NAD+. Prolonged administration of acetaldehyde, the product of alcohol dehydrogenase (ADH) mediated metabolism of ethanol, mimicked chronic ethanol exposure, whereas ADH inhibition prevented ethanol-induced IL-1β hypersecretion. Together, these results indicate that increases in iNOS and mitochondrial ROS production are critical for chronic ethanol-induced IL-1β hypersecretion, and that protracted exposure to the products of ethanol metabolism are probable mediators of NLRP3 inflammasome hyperactivation.

Ethanol and Acetaldehyde After Intraperitoneal Administration to Aldh2-Knockout Mice-Reflection in Blood and Brain Levels.

This paper reports, for the first time, on the analysis of ethanol (EtOH) and acetaldehyde (AcH) concentrations in the blood and brains of Aldh2-knockout (Aldh2-KO) and C57B6/6J (WT) mice. Animals were administrated EtOH (1.0, 2.0 or 4.0g/kg) or 4-methylpyrazole (4-MP, 82mg/kg) plus AcH (50, 100 or 200mg/kg) intraperitoneally. During the blood tests, samples from the orbital sinus of the eye were collected. During the brain tests, dialysates were collected every 5min (equal to a 15µl sample) from the striatum using in vivo brain microdialysis. Samples were collected at 5, 10, 15, 20, 25, 30 and 60min intervals post-EtOH and -AcH injection, and then analyzed by head-space GC. In the EtOH groups, high AcH levels were found in the blood and brains of Aldh2-KO mice, while only small traces of AcH were seen in the blood and brains of WT mice. No significant differences in EtOH levels were observed between the WT and the Aldh2-KO mice for either the EtOH dose. EtOH concentrations in the brain were comparable to the EtOH concentrations in the blood, but the AcH concentrations in the brain were four to five times lower compared to the AcH concentrations in the blood. In the AcH groups, high AcH levels were found in both WT and Aldh2-KO mice. Levels reached a sharp peak at 5min and then quickly declined for 60min. Brain AcH concentrations were almost equal to the concentrations found in the blood, where the AcH concentrations were approximately two times higher in the Aldh2-KO mice than in the WT mice, both in the blood and the brain. Our results suggest that systemic EtOH and AcH administration can cause a greater increase in AcH accumulation in the blood and brains of Aldh2-KO mice, where EtOH concentrations in the Aldh2-KO mice were comparable to the EtOH concentrations in the WT mice. Furthermore, detection of EtOH and AcH in the blood and brain was found to be dose-dependent in both genotypes.

The ethanol metabolite acetaldehyde induces water and salt intake via two distinct pathways in the central nervous system of rats

The sensation of thirst experienced after heavy alcohol drinking is widely regarded as a consequence of ethanol (EtOH)-induced diuresis, but EtOH in high doses actually induces anti-diuresis. The present study was designed to investigate the introduction mechanism of water and salt intake after heavy alcohol drinking, focusing on action of acetaldehyde, a metabolite of EtOH and a toxic substance, using rats. The aldehyde dehydrogenase (ALDH) inhibitor cyanamide was used to mimic the effect of prolonged acetaldehyde exposure because acetaldehyde is quickly degraded by ALDH. Systemic administration of a high-dose of EtOH at 2.5 g/kg induced water and salt intake with anti-diuresis. Cyanamide enhanced the fluid intake following EtOH and acetaldehyde administration. Systemic administration of acetaldehyde with cyanamide suppressed blood pressure and increased plasma renin activity. Blockade of central angiotensin receptor AT1R suppressed the acetaldehyde-induced fluid intake and c-Fos expression in the circumventricular organs (CVOs), which form part of dipsogenic mechanism in the brain. In addition, central administration of acetaldehyde together with cyanamide selectively induced water but not salt intake without changes in blood pressure. In electrophysiological recordings from slice preparations, acetaldehyde specifically excited angiotensin-sensitive neurons in the CVO. These results suggest that acetaldehyde evokes the thirst sensation following heavy alcohol drinking, by two distinct and previously unsuspected mechanisms, independent of diuresis. First acetaldehyde indirectly activates AT1R in the dipsogenic centers via the peripheral renin-angiotensin system following the depressor response and induces both water and salt intake. Secondly acetaldehyde directly activates neurons in the dipsogenic centers and induces only water intake.

Effect of Acetaldehyde Intoxication and Withdrawal on NPY Expression: Focus on Endocannabinoidergic System Involvement.

Acetaldehyde (ACD), the first alcohol metabolite, plays a pivotal role in the rewarding, motivational, and addictive properties of the parental compound. Many studies have investigated the role of ACD in mediating neurochemical and behavioral effects induced by alcohol administration, but very little is known about the modulation of neuropeptide systems following ACD intoxication and withdrawal. Indeed, the neuropeptide Y (NPY) system is altered during alcohol withdrawal in key regions for cerebrocortical excitability and neuroplasticity. The primary goal of this research was to investigate the effects of ACD intoxication and withdrawal by recording rat behavior and by measuring NPY immunoreactivity in hippocampus and NAcc, two brain regions mainly involved in processes which encompass neuroplasticity in alcohol dependence. Furthermore, on the basis of the involvement of endocannabinoidergic system in alcohol and ACD reinforcing effects, the role of the selective CB1 receptor antagonist AM281 in modulating NPY expression during withdrawal was assessed. Our results indicate that (i) ACD intoxication induced a reduction in NPY expression in hippocampus and NAcc; (ii) symptoms of physical dependence, similar to alcohol’s, were scored at 12 h from the last administration of ACD; and (iii) NPY levels increased in early and prolonged acute withdrawal in both brain regions examined. The administration of AM281 was able to blunt signs of ACD-induced physical dependence, to modulate NPY levels, and to further increase NPY expression during ACD withdrawal both in hippocampus and NAcc. In conclusion, the present study shows that complex plastic changes take place in NPY system during ACD intoxication and subsequent withdrawal in rat hippocampal formation and NAcc. The pharmacological inhibition of CB1 signaling could counteract the neurochemical imbalance associated with ACD, and alcohol withdrawal, likely boosting the setting up of homeostatic functional recovery.

The renaissance of acetaldehyde as a psychoactive compound: decades in the making.

The renaissance of acetaldehyde as a psychoactive compound: decades in the making.

Ethanol- and acetaldehyde-induced cholinergic imbalance in the hippocampus of Aldh2-knockout mice does not affect nerve growth factor or brain-derived neurotrophic factor

Neurotrophins, including nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), play an important role in the maintenance of cholinergic-neuron function. The objective of this study was to investigate whether ethanol (EtOH)- and acetaldehyde (AcH)- induced cholinergic effects would cause neurotrophic alterations in the hippocampus of mice. We used Aldh2 knockout (Aldh2-KO) mice, a model of aldehyde dehydrogenase 2 (ALDH2)-deficiency in humans, to examine the effects of acute administration of EtOH and the role of AcH. Hippocampal slices were collected and the mRNA and protein levels of choline acetyltransferase (ChAT), acetylcholinesterase (AChE), NGF and BDNF were analyzed 30min after the i.p. administration of EtOH (0.5, 1.0, or 2.0g/kg). We show that treatment with 2.0g/kg of EtOH decreased ChAT mRNA and protein levels in Aldh2-KO mice but not in wild-type (WT) mice, which suggests a role for AcH in the mechanism of action of EtOH. The administration of 2.0g/kg of EtOH increased AChE mRNA in both strains of mice. EtOH failed to change the levels of NGF or BDNF at any dose. Aldh2-KO mice exhibited a distinctly lower expression of ChAT and a higher expression of NGF both at mRNA and protein levels in the hippocampus compared with WT mice. Our observations suggest that administration of EtOH and elevated AcH can alter cholinergic markers in the hippocampus of mice, and this effect did not change the levels of NGF or BDNF.

C-Fos immunoreactivity in prefrontal, basal ganglia and limbic areas of the rat brain after central and peripheral administration of ethanol and its metabolite acetaldehyde

Considerable evidence indicates that the metabolite of ethanol (EtOH), acetaldehyde, is biologically active. Acetaldehyde can be formed from EtOH peripherally mainly by alcohol dehydrogenase (ADH), and also centrally by catalase. EtOH and acetaldehyde show differences in their behavioral effects depending upon the route of administration. In terms of their effects on motor activity and motivated behaviors, when administered peripherally acetaldehyde tends to be more potent than EtOH but shows very similar potency administered centrally. Since dopamine (DA) rich areas have an important role in regulating both motor activity and motivation, the present studies were undertaken to compare the effects of central (intraventricular, ICV) and peripheral (intraperitoneal, IP) administration of EtOH and acetaldehyde on a cellular marker of brain activity, c-Fos immunoreactivity, in DA innervated areas. Male Sprague-Dawley rats received an IP injection of vehicle, EtOH (0.5 or 2.5 g/kg) or acetaldehyde (0.1 or 0.5 g/kg) or an ICV injection of vehicle, EtOH or acetaldehyde (2.8 or 14.0 μmoles). IP administration of EtOH minimally induced c-Fos in some regions of the prefrontal cortex and basal ganglia, mainly at the low dose (0.5 g/kg), while IP acetaldehyde induced c-Fos in virtually all the structures studied at both doses. Acetaldehyde administered centrally increased c-Fos in all areas studied, a pattern that was very similar to EtOH. Thus, IP administered acetaldehyde was more efficacious than EtOH at inducing c-Fos expression. However, the general pattern of c-Fos induction promoted by ICV EtOH and acetaldehyde was similar. These results are consistent with the pattern observed in behavioral studies in which both substances produced the same magnitude of effect when injected centrally, and produced differences in potency after peripheral administration.

Abuse Potential of Non-Nicotine Tobacco Smoke Components: Acetaldehyde, Nornicotine, Cotinine, and Anabasine

This review identified published animal studies evaluating the possible abuse potential of acetaldehyde, nornicotine, cotinine, and anabasine based on five commonly used paradigms. These include their effects on midbrain dopamine (DA) levels, drug discrimination and substitution for known drugs of abuse, place conditioning, self-administration behavior, and somatic withdrawal symptoms. Acetaldehyde had mixed effects on midbrain DA levels and drug discrimination; however, it consistently produced a conditioned place preference and supported self-administration. The single available study on withdrawal found that cessation of acetaldehyde administration resulted in a somatic withdrawal syndrome. Nornicotine increased DA in the midbrain, especially in the nucleus accumbens. Although there are no data on place conditioning, it substituted for nicotine in drug discrimination testing, partially substituted for cocaine and amphetamine, and, though only a single study, supported self-administration. Anabasine increased midbrain DA levels and that it partially substituted for nicotine in drug discrimination testing. Cotinine increased midbrain DA levels and substituted for nicotine. The existing literature suggests that acetaldehyde and nornicotine likely possess abuse potential, with anabasine having possible abuse potential. Although some cotinine data were available, it was insufficient to draw conclusions about possible abuse potential. Further research is needed to determine the role of minor alkaloids on tobacco dependence.

Ethanol and acetaldehyde mediate folic acid and human papillomavirus-induced proliferation of oral squamous cell carcinoma cells in vitro

Background Although great scientific emphasis has been placed upon HPVas the primary cause of cervical cancers and its involvement in carcinogenic progression of other cancers, less attention has been focused on the secondary factors that are associated with progression from subclinical HPV infection to invasive carcinoma. Among the secondary factors that limit virus production and carcinogenic progression is CpG methylation of the HPV genome. Several studies now confirm that CpG site-specific methylation of HPV DNA, mediated in part by folate availability, is sufficient to suppress neoplastic progression. In contrast, demethylation or hypomethylation of HPV-DNA sequences is required for transformation, revealing the importance of preferential DNA methylation at CpG sites in the HPV long control region (LCR) between L1 and E6 HPV genes, in addition to the tumor suppressor sites in p53 exons 248 and 273. Because HPV has the potential to initiate oncogenesis, and also to modulate oral cancer growth and folate plays a central role in mediating the availability of methyl groups for CpG-specific DNA methylation (modulating both p53 and HPV mRNA expression) – an investigation of these inter-connected and inter-related mechanisms in oral cancers must be undertaken. In addition, ethanol and acetaldehyde may also play critical roles in determining folate availability, and are primary risk factors for the development of oral cancers, which makes the evaluation of these interconnected metabolic pathways critically important. Materials and methods Using a comprehensive series of integrated in vitro assays, including proliferation, viability and mRNA analysis using RT-PCR, distinct effects of ethanol and acetaldehyde administration were observed in the oral cancer cell lines, CAL27, SCC15 and SCC25. In addition, the growth modulating effects of HPV infection and FA supplementation were also examined.

Anxiogenic and stress-inducing effects of peripherally administered acetaldehyde in mice: Similarities with the disulfiram–ethanol reaction

Peripheral accumulation of acetaldehyde, the first metabolite of ethanol, produces autonomic responses in humans called “flushing”. The aversive characteristics of flushing observed in some populations with an isoform of aldehyde dehydrogenase (ALDH2) less active, are the basis for treating alcoholics with disulfiram, an ALDH inhibitor. Although ethanol and centrally formed acetaldehyde have anxiolytic effects, peripheral accumulation of acetaldehyde may be aversive in part because it is anxiogenic. ObjectivesWe investigated the effect of direct administration of acetaldehyde on behavioral measures of anxiety and on hormonal markers of stress in mice. The impact of disulfiram on the anxiolytic actions of ethanol was evaluated. Acetate (a metabolite of acetaldehyde) was also studied. MethodsCD1 male mice received acetaldehyde (0, 25, 50, 75 or 100mg/kg) at different time intervals and were assessed in the elevated plus maze and in the dark–light box. Corticosterone release after acetaldehyde administration was also assessed. Additional experiments evaluated the impact of disulfiram on the anxiolytic effect of ethanol (0 or 1mg/kg), and the effect of acetate on the plus maze. ResultsDirect administration of acetaldehyde (100mg/kg) had an anxiogenic effect at 1, 11 or 26min after IP administration. Acetaldehyde was ten times more potent than ethanol at inducing corticosterone release. Disulfiram did not affect behavior on its own, but blocked the anxiolytic effect of ethanol at doses of 30 and 60mg/kg, and had an anxiogenic effect at the highest dose (90mg/kg) when co-administered with ethanol. Acetate did not affect any of the anxiety parameters. ConclusionsPeripheral administration or accumulation of acetaldehyde produces anxiogenic effects and induces endocrine stress responses. This effect is not mediated by its metabolite acetate.

Acute effects of ethanol and acetaldehyde on plasma phosphate level.

Oral administration of ethanol in a dose of 65 mmol kg-1 produced marked change of plasma phosphate level in rabbits. Hypophosphataemia was observed for the first 2 h after administration followed by significant increase of plasma phosphate at 5 h. Hypophosphataemia did not appear when ethanol was given to the rabbits pretreated with pyrazole. When animals were injected with disulfiram in advance, the duration of hyperphosphataemia due to ethanol was prolonged. Administration of acetaldehyde at a dose of 1.5 mmol kg-1 produced hyperphosphataemia. In this study, plasma phosphate was not associated with change in calcium level. These results suggest that the hypophosphataemia observed was related to the metabolic process of ethanol utilizing alcohol dehydrogenase, and that acetaldehyde, a metabolite of ethanol, might induce the hyperphosphataemia in the animals.

The effects of acetaldehyde on nicotine-induced transmitter levels in young and adult brain areas

The aim of the present study was to examine the effect of acetaldehyde administration on neurotransmitters in the presence of nicotine in brain areas associated with cognition and reward. We assayed these effects via microdialysis in conscious freely moving male Sprague-Dawley rats. It was reported that low doses of acetaldehyde enhance nicotine self-administration in young, but not in adult rats. Since nicotine enhances reward and learning, while acetaldehyde is reported to enhance reward but inhibit learning, acetaldehyde thus would be likely to stimulate reward without stimulating learning. We hoped that examining the effects of acetaldehyde (on nicotine-mediated neurotransmitter changes) would help to distinguish reward mechanisms less influenced by learning mechanisms. To avoid the aversive effect of acetaldehyde, we used a low dose of acetaldehyde (0.16 mg/kg) administered after nicotine (0.3 mg/kg). We analyzed six brain regions: nucleus accumbens shell (NAccS), ventral tegmental area (VTA), ventral and dorsal hippocampus (VH and DH), and prefrontal and medial temporal cortex (PFC, MTC), assaying dopamine (DA), norepinephrine (NE) and serotonin (5-HT) and their metabolites in young and adult rats. The effect of acetaldehyde on nicotine-induced transmitter changes was different in young as compared to adult rat brain regions. In the NAccS of the young, DA was not affected while NE and 5-HT were increased. In the adult in this area DA and NE were decreased, while 5-HT was not altered. In other areas also in many cases, the effect of acetaldehyde in the young and in the adult was different. As an example, acetaldehyde administration increased NE in young and decreased NE in adult DH. We found stimulation of nicotine-induced changes by acetaldehyde in seven instances – six of these were observed in areas in young brain, NE in four areas (NAccS, DH, VH, and PFC), and 5-HT in two (NAccS and DH). Only one increase was noted in adult brain (DA in VTA). Inhibition of nicotine-induced changes by acetaldehyde was noticed in four young brain areas (DA in PFC and MTC, 5-HT in VTA, and VH) and in 13 adult brain areas (DA in NAccS, DH, VH, PFC, MTC, NE in NAccS, DH, PFC, MTC, and 5-HT in DH, VH, MTC, and PFC). Thus acetaldehyde was more stimulatory in young and more inhibitory in the adult brain areas tested, which could explain its stimulating nicotine reward only in young animals. That increases in NE were noted only in young, decreases in NE only in adult brain areas further suggest the role of NE in the age-dependent response. In general, six areas showed some increase and four showed decrease in the young versus one showing increase and thirteen showing decrease in the adult. Clearly the effects of acetaldehyde in young animals are different from those in adult animals. Because acetaldehyde did not induce elevated DA levels in the NAccS of the young, we believe that the higher reward in the young caused by acetaldehyde is not likely due to DA changes in the accumbens. The increase of NE and 5-HT in the brain areas of the young only raises the possibility that they may play an important role in reward in some cases when DA in the accumbens does not. Areas involved in cognitive mechanisms and a number of transmitters seem to play a role in reward stimulation.

Motor stimulant effects of ethanol and acetaldehyde injected into the posterior ventral tegmental area of rats: role of opioid receptors

A recently published study has shown that microinjections of ethanol, or its metabolite, acetaldehyde into the substantia nigra pars reticulata, are able to produce behavioral activation in rats. Another brain site that could participate in such effects is the ventral tegmental area (VTA). We have investigated the locomotor-activating effects of local microinjections of ethanol and acetaldehyde into the posterior VTA of rats and the role of opioid receptors in such effects. Cannulae were placed into the posterior VTA to perform microinjections of ethanol (75 or 150 nmol) or acetaldehyde (25 or 250 nmol) in animals not previously microinjected or microinjected with either the nonselective opioid antagonist naltrexone (13.2 nmol) or the irreversible antagonist of the micro-opioid receptors beta-funaltrexamine (beta-FNA; 2.5 nmol). After injections, spontaneous activity was monitored for 60 min. Injections of ethanol or acetaldehyde into the VTA increased the locomotor activity of rats with maximal effects at doses of 150 nmol for ethanol and 250 nmol for acetaldehyde. These locomotor-activating effects were reduced by previously administering naltrexone (13.2 nmol) or beta-FNA (2.5 nmol) into the VTA. The posterior VTA is another brain region involved in the locomotor activation after the intracerebroventricular administration of ethanol or acetaldehyde. Our data indicate that opioid receptors, particularly the micro-opioid receptors, could be the target of the actions of these compounds in the VTA. These results are consistent with the hypothesis that acetaldehyde could be a mediator of some ethanol effects.

Infusions of acetaldehyde into the arcuate nucleus of the hypothalamus induce motor activity in rats

Aims The hypothalamic arcuate nucleus (ARH) is one of the brain regions with the highest levels of catalase expression. Acetaldehyde, metabolized from ethanol in the CNS through the actions of catalase, has a role in the behavioral effects observed after ethanol administration. In previous studies acetaldehyde injected in the lateral ventricles or in the substantia nigra reticulata (SNR) mimicked the behavioral stimulant effects of centrally administered ethanol. Main methods In the present study we assessed the effects of acetaldehyde administered either into the ARH into a dorsal control or into the third ventricle on locomotion and rearing observed in 30 min sessions in an open field. Key findings Acetaldehyde injected into the ARH induced horizontal locomotion and rearing for 20 min. In contrast, administration of acetaldehyde into a control site dorsal to the ARH did not have any effect on locomotion. Although acetaldehyde administration into the third ventricle also induced locomotion, the time course for the effect in this area was different from the time course following ARH injections. Acetaldehyde in the ARH produced a long lasting induction of locomotion, while with intraventricular injections the effects disappeared after 5 min. Significance The present results are consistent with previous studies demonstrating that acetaldehyde is an active metabolite of ethanol, which can have locomotor stimulant properties when administered in the ventricular system of the brain or into specific brain nuclei. Some brain nuclei rich in catalase (i.e.; SNR and ARH) could be mediating some of the locomotor stimulant effects of ethanol through its conversion to acetaldehyde.