Alcohol intoxication and withdrawal: the role of nitric oxide

Nitric Oxide Signaling Pathway in Ventral Tegmental Area is Involved in Regulation of 7,8-Dihydroxyflavone on Alcohol Consumption in Rats

We recently reported that intraperitoneal injection of 7,8-dihydroxyflavone (7,8-DHF), a brain-derived neurotrophic factor-mimicking small compound, could attenuate alcohol-related behaviors in a two-bottle choice ethanol consumption procedure (IA2BC) in rats via tropomyosin receptor kinase B in the ventral tegmental area (VTA), which is closely related to alcohol use disorder. However, the detailed mechanisms underlying the regulation of 7,8-DHF on alcohol drinking behavior remain elusive. In this study, we determined the role of nitric oxide (NO), a pleiotropic signaling molecule, in the VTA in the action of 7,8-DHF upon alcohol drinking behavior. Intermittent alcohol exposure led to the overexpression of NO in the VTA, especially 72 h after withdrawal from four weeks of ethanol exposure in IA2BC rats. A higher amount of alcohol intake was also found at the same time point, consistent with the overexpression of NO in the VTA. Microinjection of NG-Nitro-l-Arginine Methyl Ester, (NO synthase inhibitor) or 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NO scavenger) into the VTA inhibited alcohol intake, whereas application of S-Nitroso-N-acetyl-DL-penicillamine (SNAP, the NO donor) in the VTA further enhanced alcohol consumption in IA2BC rats. Interestingly, either 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (a sGC inhibitor) or KT5823 [a selective protein kinase G (PKG) inhibitor] blocked NO's enhancing effect on ethanol intake. Intraperitoneal injection of 7,8-DHF reduced the overexpression of NO; SNAP microinjected into the VTA reversed the inhibitory effects of 7,8-DHF on alcohol consumption. Our findings suggest that NO-cGMP-PKG might be involved in regulation of 7,8-DHF on alcohol consumption in IA2BC rats.

Acute withdrawal: diagnosis and treatment

Symptoms of alcohol withdrawal range in severity from mild "hangover" to fatal delirium tremens (DTs). Tremor, hallucinosis, and seizures usually occur within 48 hours of abstinence. Seizures tend to be generalized without focality, occurring singly or in a brief cluster, but status epilepticus is not unusual. DTs usually appears after 48 hours of abstinence and consists of marked inattentiveness, agitation, hallucinations, fluctuating level of alertness, marked tremulousness, and sympathetic overactivity. The mainstay of treatment for alcohol withdrawal is benzodiazepine pharmacotherapy, which can be used to control mild early symptoms, to prevent progression to DTs, or to treat DTs itself. Alternative less evidence-based pharmacotherapies include phenobarbital, anticonvulsants, baclofen, gamma-hydroxybutyric acid, beta-blockers, alpha-2-agonists, and N-methyl-d-aspartate receptor blockers. Treatment of DTs is a medical emergency requiring heavy sedation in an intensive care unit, with close attention to autonomic instability, fever, fluid loss, and electrolyte imbalance. Frequent comorbid disorders include hypoglycemia, liver failure, pancreatitis, sepsis, meningitis, intracranial hemorrhage, and Wernicke-Korsakoff syndrome.

Effects of alcohol withdrawal on cardiovascular system

Alcohol withdrawal syndrome (AWS) develops after cessation of alcohol intake in alcoholic patients characterizing psychiatric symptoms and changes in autonomous nervous systems. We studied cardiovascular changes during different phases of AWS (1, 2, 3 and 10 days after admission for detoxification; n=34) and compared them with those in early recovery (at least 1 month of abstinence; n=30). The results study showed that cardiovascular system underwent significant changes during AWS characterizing the decrease of heart rate, systolic and diastolic blood pressures, and total peripheral resistance. Stroke index was lower during AWS than in early recovery. As the decreased stroke index was compensated by increased heart rate, cardiac index did not differ during AWS from that in early recovery. Increased functioning of noradrenaline (along with other central and peripheral regulating mechanisms) may be an important factor associated with cardiovascular changes in AWS. Normalization of this function after AWS leads to returning of cardiovascular parameters to baseline levels.

Nitric oxide physiology and pathology

Nitric oxide (NO) is just one member of a new class of gaseous signalling molecules with fundamental actions in biology. In higher vertebrates it has key roles in maintaining haemostasis and in smooth muscle (especially vascular smooth muscle), neurons and the gastrointestinal tract. It is intimately involved in regulating all aspects of our lives from waking, digestion, sexual function, perception of pain and pleasure, memory recall and sleeping. Finally, the way it continues to function in our bodies will influence how we degenerate with age. It will likely play a role in our deaths through cardiovascular disease, stroke, diabetes and cancer. Our ability to control NO signalling and to use NO effectively in therapy must therefore have a major bearing on the future quality and duration of human life.

Differential central NOS-NO signaling underlies clonidine exacerbation of ethanol-evoked behavioral impairment

BACKGROUND

The molecular mechanisms that underlie clonidine exacerbation of behavioral impairment caused by ethanol are not fully known. We tested the hypothesis that nitric oxide synthase (NOS)-derived nitric oxide (NO) signaling in the locus coeruleus (LC) is implicated in this phenomenon.

METHODS

Male Sprague-Dawley rats with intracisternal (i.c.) and jugular vein cannulae implanted 6 days earlier were tested for drug-induced behavioral impairment. The latter was assessed as the duration of loss of righting reflex (LORR) and rotorod performance every 15 minutes until the rat recovered to the baseline walk criterion (180 seconds). In a separate cohort, we measured p-neuronal NOS (nNOS), p-endothelial NOS (eNOS), and p-ERK1/2 in the LC following drug treatment, vehicle, or NOS inhibitor.

RESULTS

Rats that received clonidine [60 Ig/kg, i.v. (intravenous)] followed by ethanol (1 or 1.5 g/kg, i.v.) exhibited synergistic impairment of rotorod performance. Intracisternal pretreatment with nonselective NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 0.5 mg) or selective nNOS inhibitor N-propyl-L-arginine (1 microg) exacerbated the impairment of rotorod performance caused by clonidine-ethanol combination. Exacerbation of behavioral impairment was caused by L-NAME enhancement of the effect of ethanol, not clonidine. L-NAME did not influence blood ethanol levels; thus, the interaction was pharmacodynamic. LORR caused by clonidine (60 microg/kg, i.v.)-ethanol (1 g/kg, i.v.) combination was abolished by selective inhibition of central eNOS (L-NIO, 10 microg i.c.) but not by nNOS inhibition under the same conditions. Western blot analyses complemented the pharmacological evidence by demonstrating that clonidine-ethanol combination inhibits phosphorylation (activation) of nNOS (p-nNOS) and increases the level of phosphorylated eNOS (p-eNOS) in the LC; the change in p-nNOS was paralleled by similar change in LC p-ERK1/2. NOS inhibitors alone did not affect the level of nitrate/nitrite, p-nNOS, p-eNOS, or p-ERK1/2 in the LC.

CONCLUSIONS

Alterations in NOS-derived NO in the LC underlie clonidine-ethanol induced behavioral impairment. A decrease in nNOS activity, due at least partly to a reduction in nNOS phosphorylation, mediates rotorod impairment, while enhanced eNOS activity contributes to LORR, elicited by clonidine-ethanol combination.

Role of the nNOS gene in ethanol-induced conditioned place preference in mice

Nitric oxide (NO) produced by neuronal nitric oxide synthase (nNOS) has a role in synaptic plasticity, and evidence suggests its role in a range of effects produced by alcohol in the central nervous system. The aim of the current study was to investigate the role of the nNOS gene in the development of ethanol-induced conditioned place preference (CPP) in mice. The CPP paradigm is designed to investigate the reinforcing properties of drugs of abuse and the development of maladaptive behaviors, such as conditioned response to drug-associated stimuli, after repeated drug exposure. Adult male and female wild type (WT) and nNOS knockout (KO) mice on a mixed B6;129S genetic background were trained by a morning saline session and afternoon ethanol (1, 2, and 3 g/kg; intraperitoneally) session for 4 days. Place preference in a drug-free state was recorded on the following day. Results show that WT males and females developed robust CPP, whereas nNOS KO mice did not (with the exception of female nNOS KO mice conditioned by 2 g/kg ethanol). The differential response of WT and nNOS KO mice was not due to genotypic differences in motor behavior. To investigate if the absence of the nNOS gene causes specific impairment in processing the motivational effect of ethanol or an overall impairment in associative learning, WT and nNOS KO mice were trained by LiCl (150 mg/kg) which causes conditioned place aversion (CPA). Results show that both WT and nNOS KO mice developed significant CPA. The findings that the absence of the nNOS gene impaired ethanol-induced CPP but not LiCl-induced CPA suggest that NO signaling has a specific role in processing the motivational effect of ethanol. Hence, inhibition of nNOS may attenuate the development of maladaptive behaviors associated with alcohol exposure.

Ethanol-induced behavioral sensitization in adolescent and adult mice: role of the nNOS gene

BACKGROUND

In the brain, nitric oxide (NO) produced by neuronal nitric oxide synthase (nNOS) has a role in synaptic plasticity. Recent evidence suggests the role of NO in a variety of effects produced by alcohol in the central nervous system. The current study investigated the role of the nNOS gene in the development of behavioral sensitization to ethanol in adolescent and adult mice.

METHODS

Adolescent and adult wild type (WT; B6;129SF2) and nNOS knockout (KO; B6;129S4-Nos1) mice of both sexes received saline or ethanol (1.5 g/kg; intraperitoneally) for 5 consecutive days, and locomotor activity was recorded daily. The locomotor response to challenge ethanol and saline injections was investigated at various time points following withdrawal from ethanol.

RESULTS

Adolescent WT but not nNOS KO mice developed a long-lasting sensitized response to ethanol as well as context-dependent hyperlocomotion (in response to saline) from adolescence through adulthood; sex-dependent differences were not observed. Compared to adolescent WT mice, adult WT males developed a short-term sensitized response to ethanol and context-dependent hyperlocomotion; adult WT females showed only short-term context-dependent hyperlocomotion. Adult nNOS KO males (like their adolescent counterparts) did not develop behavioral sensitization; no significant differences between adult nNOS KO and WT females were observed. Blood ethanol concentrations did not show genotype- or sex-dependent differences.

CONCLUSIONS

(1) The nNOS gene is required for the development of behavioral sensitization to ethanol in adolescent male and female mice. (2) Adolescent exposure to ethanol results in long-lasting behavioral sensitization through adulthood, while adult exposure to ethanol results in a shorter behavioral sensitization. (3) Sex-dependent differences are observed when ethanol exposure begins in adulthood but not in adolescence. (4) Ethanol-induced behavioral sensitization in adulthood is nNOS-dependent in males but not in females. Taken together, results suggest genotype-, ontogeny-, and sex-dependent differences in the development of behavioral sensitization to ethanol.

Possible mechanism of acute effect of ethanol on intestinal IgA expression in rat

The purpose of this study was to investigate the possible mechanism of acute effect of ethanol on IgA expression in rat intestine. To this end, adult female Wistar rats showing diestrus day 1 were treated with (a) ethanol (2 or 4 g/kg, i.p.); (b) N omega-nitro-L-arginine-methyl ester (L-NAME), which inhibits the activity of all isoforms of nitric oxide synthase, (30 mg/kg, s.c.) followed by ethanol 3 h later; and (c) L-NAME (30 mg/kg, s.c.) followed by saline 3 h later. Saline-injected and untreated rats were used as controls. The animals were sacrificed 0.5 h after ethanol administration. Intestinal expression of IgA was evaluated by both immunohistochemistry and Western immunoblotting. Morphometric analysis showed that acute ethanol treatment increased the number of IgA-immunoreactive cells in a dose-dependent manner. Pretreatment with L-NAME abolished this action of alcohol. Injection of L-NAME followed by saline had no influence on the number of IgA+cells. The results, obtained by Western immunoblotting, paralleled our immunohistochemical findings. Taken together, these data suggest that acute effect of ethanol on intestinal IgA might be mediated by endogenous nitric oxide.

Nitric oxide mediates cardiovascular symptoms in alcohol withdrawal

We studied whether nitric oxide is involved in cardiovascular symptoms in alcohol withdrawal. Cardiovascular effects of isosorbide dinitrate (ISDN; 20 mg sublingually), a nitric oxide donor were compared in 21 alcohol-dependent subjects during alcohol withdrawal (n=11) on days 1, 2, 3, and 10 to those during remission (n=10; duration=60.7+/-10.5 days). Cardiovascular parameters were measured non-invasively. The levels of systolic and diastolic blood pressure, total peripheral resistance were significantly higher in patients with withdrawal than in remission. Same cardiovascular parameters showed different response to ISDN during withdrawal when compared to remission. The differences were largest during the initial phase (1-2 days) of withdrawal. Nitric oxide may mediate at least some cardiovascular symptoms in withdrawal.

Dietary restriction protects against chronic-ethanol-induced changes in exploratory behavior in Wistar rats

Chronic ethanol intake causes various types of neural damage and behavioral impairments, probably acting through oxidative stress and excitotoxicity, while dietary restriction is considered by some authors to protect the central nervous system from these kinds of damage. In the present study, a factorial experimental design was used to investigate the effects of chronic ethanol and dietary restriction treatments, associated or not, on Wistar rats' exploratory behavior, spatial memory aspects and cortical and hippocampal acetylcholinesterase (AChE) activity. Dietary restriction lasted for the whole experiment, while ethanol treatment lasted for only 3 weeks. Despite the short ethanol treatment duration, for two behavior categories assessed, moving and rearing, an interaction was observed between the effects of chronic ethanol and dietary restriction. There were no significant differences in AChE activities among the groups. Cerebellar neural nitric oxide synthase (nNOs) activity was measured as a first step to assess oxidative stress. Dietary restriction significantly reduced NO formation. The present results indicate that dietary restriction might exert a protective effect against chronic-ethanol-induced changes in exploratory behavior. It is hypothesized that the mechanisms underlying this protection can involve prevention of oxidative stress.

The influence of gastric pentadecapeptide BPC 157 on acute and chronic ethanol administration in mice

The stable gastric pentadecapeptide BPC 157 (GEPPPGKPADDAGLV, M.W.1419), which was promising in inflammatory bowel disease (PL-10, PLD-116, PL-14736, Pliva) trials, protects against both acute and chronic alcohol-induced lesions in stomach and liver, but also, given peripherally, affects various centrally mediated disturbances. Now, in male NMRI mice BPC 157 (10 pg intraperitoneally, 10 ng and 10 microg, intraperitoneally or intragastrically) (i) strongly opposed acute alcohol (4 g/kg intraperitoneally) intoxication (i.e., quickly produced and sustained anesthesia, hypothermia, increased ethanol blood values, 25% fatality, 90-min assessment period) given before or after ethanol, and (ii) when given after abrupt cessation of ethanol (at 0 or 3 or 7 h withdrawal time), attenuated withdrawal (assessed through 24 hours) after 20%-alcohol drinking (7.6 g/kg) through 13 days, with provocation on the 14th day.

Litter has an effect on the behavioural changes caused by the administration of the nitric oxide synthase inhibitor NG-nitro-L-arginine and ethanol in mice

The aim of the work was to study the effects of litter and the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine (L-NOARG) on the behaviour of mice after acute and chronic ethanol administration and withdrawal. Male outbred NIH/S mice, from 21 litters, were distributed among experimental groups and subjected to acute and chronic ethanol administration. After acute or chronic ethanol administration, the effects of L-NOARG on the behaviour of mice in the plus-maze test were studied. Acute ethanol (1 g/kg, i.p.), L-NOARG (20 and 40 mg/kg, i.p.) and their combination induced an anxiolytic effect. Furthermore, the values for the representatives of different litters tended to be either above or below the group mean, irrespective of the drug treatment. Chronic ethanol administration (23 days by inhalation) induced an anxiolytic effect and ethanol withdrawal induced an anxiogenic effect in the plus-maze. The administration of L-NOARG (20 mg/kg, i.p.) induced an anxiolytic effect in control mice and had no effect on ethanol-intoxicated mice, but attenuated the anxiogenic effect of ethanol withdrawal in the plus-maze. However, after chronic ethanol administration and withdrawal, litter had no effect on the behaviour of mice. If the litter is a significant determinant in the behaviour of outbred mice, then the use of information about the litter origin of animals could serve for the purposes of reduction. But only if this information is available from breeders.

Formation of ethyl nitrite in vivo after ethanol administration

The purpose of the current study was to ascertain whether ethyl nitrite could be detected in vitro from the reaction of ethanol with peroxynitrite, as well as after administration of ethanol to mice. Ethyl nitrite analyte was determined by using gas chromatography--mass spectrometry with headspace analysis with the use of a solid-phase microextraction device. Peroxynitrite was allowed to react with ethanol under a variety of conditions in vitro. Ethyl nitrite was generated when peroxynitrite was allowed to react with ethanol. Male, inbred short-sleep mice were injected intraperitoneally with either ethanol [5.2 g/kg; 15.0% (weight/volume) ethanol in saline] or a 50:50 mixture of deuterium-labeled ethanol (D5-ethanol) and ethanol. Blood samples, as well as whole brain and liver sections, were obtained from mice 30 min later for determination of ethanol, D5-ethanol, ethyl nitrite, and deuterium-labeled ethyl nitrite (D5-ethyl nitrite). Time courses for the appearance of ethyl nitrite in blood samples, as well as in whole brain and liver sections, obtained from mice were carried out. After ethanol administration, ethyl nitrite was detected and quantitated in mouse blood, brain, and liver. A small fraction of ethyl nitrite was present. When a 50:50 mixture of ethanol and D5-ethanol was given to animals, both ethyl nitrite and D5-ethyl nitrite were found in blood and brain in approximately the same ratio as that of ethanol and D5-ethanol. The level of D5-ethyl nitrite in liver was more than twice that of ethyl nitrite, indicating a possible isotope effect in the metabolism of ethyl nitrite. Ethyl nitrite is a new metabolite of ethanol in vivo. The mechanism of ethyl nitrite formation is most likely the reaction of ethanol with peroxynitrite generated in vivo from nitric oxide.

Prolonged exposure to intermittent alcohol vapors decreases the ACTH as well as hypothalamic nitric oxide and cytokine responses to endotoxemia

BACKGROUND

Prolonged exposure to alcohol blunts the response of the hypothalamic-pituitary-adrenal (HPA) axis to various stressors, including the systemic injection of a lipopolysaccharide (LPS). We previously showed that decreased synthesis of the hypothalamic peptides corticotropin-releasing factor (CRF) and vasopressin (VP) played a central role in this phenomenon. However, the mechanisms that lead to decreased hypothalamic neuronal activity have not been identified. In the present work, we tested the hypothesis that alcohol decreased signals that are elicited by LPS and that stimulate hypothalamic CRF and VP synthesis, namely nitric oxide (NO) and the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6).

METHODS

Adult male rats were exposed to intermittent (5 hr/day) alcohol vapors for 5 days. Control animals were kept in comparable chambers but not exposed to the vapors. On day 6, the animals received an injection of LPS through permanent indwelling intravenous cannulae. The dependent variables were plasma ACTH levels measured by IRMA (immunoradiometric assay); pituitary and hypothalamic TNF-alpha and IL-6 mRNA levels measured by RNase protection assay; basal activity of neuronal NO synthase measured by conversion of [14C]arginine to [14C]citrulline, the constitutive enzyme that synthesizes NO and modulates the influence of this gas on LPS-induced HPA axis activity; and basal and LPS-induced levels of citrulline (an index of NO formation) in the hypothalamus, measured by immunocytochemistry.

RESULTS

After injection with LPS, rats that were pretreated with alcohol exhibited a significantly (p < 0.01) decreased release of ACTH, compared with controls. There was no difference in basal NO synthase activity or hypothalamic citrulline levels. In contrast, LPS-induced hypothalamic citrulline levels were significantly (p < 0.01) lower in alcohol-exposed rats, as were pituitary TNF-alpha and IL-6 transcripts. In the hypothalamus, the TNF-alpha but not IL-6 response to LPS was also reduced.

CONCLUSIONS

These results indicate that prolonged exposure to alcohol decreases the ACTH, hypothalamic NO and TNF-alpha, and pituitary TNF-alpha and IL-6 responses to LPS. This suggests that altered NO and proinflammatory cytokine levels in the brain may modulate the inhibitory influence exerted by alcohol on the HPA axis response to endotoxemia.

Mechanisms of cardiovascular dysregulation during alcohol withdrawal

Alcohol withdrawal (AW) is often accompanied by functional cardiovascular abnormalities which return to normal in few days. However, in some patients, they can predict future alterations in the cardiovascular system, even if they remain in abstinence. These changes are mediated by several central and peripheral mechanisms closely related to AW. The level of activation in the sympathetic nervous system is an important factor regulating the functioning of the cardiovascular system in AW directly and/or indirectly with L-type calcium channels and nitric oxide (NO). Other factors may contribute to cardiovascular alterations in AW including the renin-angiotensin-aldosterone system, vasopressin, cortisol and sodium sensitivity. Monitoring of the cardiovascular system is needed in patients undergoing treatment for AW. The patients with elevated systolic blood pressure (SBP) and diastolic blood pressure (DBP) after resolution of AW may require a fuller work-up of their cardiovascular system.

Altered cardiovascular responses to nitrosorbide in alcohol withdrawal

The cardiovascular effects and pharmacokinetics of a single dose (20 mg sublingually) of isosorbide dinitrate (ISDN) were studied in 9 alcohol-dependent men during alcohol withdrawal syndrome (AW) on day 1 and after the resolution of AW on day 10. At the onset of AW, ISDN and its metabolites caused a hypotensive effect, which was increased on day 10, while no differences in ISDN-induced decrease in stroke volume were observed. Tachycardiac response to ISDN was more pronounced at onset of AW. On day 10, the AUC(0-1.5 h), C(max) and t((1/2)) of ISDN were increased compared with day 1. The results of this study suggest that nitric oxide may modulate the cardiovascular system in AW.

Influence of drugs acting on nitric oxide-dependent pathways on ethanol tolerance in rats

RATIONALE

Our previous studies have shown that the inhibition of nitric oxide (NO) synthesis with drugs administered either by systemic or ICV routes blocks the development of tolerance to some of the effects of ethanol.

OBJECTIVES

The aim of this study was to further investigate the role of NO-dependent pathways in tolerance to the incoordinating effect of ethanol through ICV administration of drugs that activate or interfere with NO-dependent pathways.

METHODS

Male Wistar rats were pretreated with IP ethanol (2.7 g/ kg) or saline before receiving ICV injections of the soluble guanylyl cyclase (sGC) inhibitors methylene blue (30 nmol), 6(phenylamino)-5,8-quinolinedione (LY83583, 10 nmol), 1H-(1,2,4)-oxodiazolo (4,3-a)quinoxalin-1-one (ODQ, 1 nmol), and 4H-8-bromo-1,2,4-oxadiazolo (3,4-d)benz(b)(1,4)oxazin-1-one (NS2028, 10 nmol), or the respective control solutions. The animals were tested on the tilt plane apparatus. Tolerance was assessed 24 h after the first ethanol injection, by administering ethanol to all animals and re-testing them on the tilt plane. The effects of the cyclic guanylate 3',5'-monophosphate (cGMP) analogue, 8-bromo-cGMP (40 nmol or 80 nmol) and of the NO donors S-nitroso-N-acetylpenicillamine (SNAP, 40 or 80 nmol) and sodium nitroprusside (SNP, 40 or 80 nmol) were also studied.

RESULTS

All sGC inhibitors significantly blocked rapid tolerance, whereas SNP (40 nmol) and 8-bromo-cGMP (80 nmol) increased the magnitude of ethanol tolerance (ANOVA+Tukey's test).

CONCLUSIONS

The present results suggest that activation or inhibition of NO-dependent pathways increases or blocks rapid tolerance, respectively. These results give additional support to the hypothesis that brain NO plays a role in the development of tolerance to ethanol, but it remains to be confirmed if the same basic cellular mechanisms are also applicable to tolerance to other behavioural and/or physiological effects of this drug.

The effect of chronic ethanol administration on nitric oxide-mediated responses in rat isolated trachea preparation

1. In the present study, we investigated the effect of chronic ethanol administration on nitric oxide (NO)-mediated responses in rat isolated trachea preparation. 2. Ethanol was given to rats in a modified liquid diet for 21 days. Isolated tracheal rings were then used to obtain responses to electrical field stimulation (EFS) after precontraction with 100 microM histamine. The parameters of field stimulation were as follows: supramaximal voltage of 50 V, 0.5 ms duration, 10-s train; 0.5, 1, 3, 5, 10, 20, 30 and 50 Hz at 2-min intervals. The effects of L-and D-arginine (10(-6) M) on the responses to field stimulation (10-20 Hz) were studied. In other experiments, we tested the effects of N(omega)-nitro-L-arginine methyl ester (L-NAME, 10(-6)-10(-5) M) and SIN-1 (10(-6)-10(-5) M) on the responses to field stimulation. 3. Electrical field stimulation induced relaxation responses in the tracheal rings precontracted with histamine from control- and ethanol-treated rats. The relaxation responses induced by EFS were significantly reduced in the tracheal rings precontracted with histamine from ethanol dependent group. The responses induced by EFS in both groups were completely abolished by tetrodotoxin (1 microM), but unaffected by hexamethonium (1 microM). Incubation with D-arginine did not cause statistically significant increases in relaxation responses to EFS in both groups. L-Arginine (10(-6) M) caused statistically significant increases in relaxation responses to EFS in control rats, but not in ethanol dependent rats. Incubation with L-NAME (10(-6)-10(-5) M) caused statistically significant inhibition of the relaxation responses to EFS in both groups. SIN-1 (10(-6)-10(-5) M) induced significantly increase in relaxation responses to EFS in both groups. 4. Our results suggest that the possible mechanism responsible for inhibition of tracheal inhibitory responses to EFS in ethanol-dependent rats may be a reduction in production of NO and in the uptake of L-arginine.

A review of the causes of central pontine myelinosis: yet another apoptotic illness?

One of the well recognized stimuli for central pontine myelinosis (CPM) is the rapid correction of chronic hyponatraemia. Conventionally this has been perceived to lead to pontine glial cell swelling through osmosis and eventually to cell death. However, although a purely osmotic argument has been central to any patho-physiological understanding of CPM, there are deficiencies in this approach that do not account for why certain individuals develop CPM with relatively mild osmotic insults. Here we review the varying aetiologies of CPM and propose a novel hypothesis for CPM causation by suggesting that individuals predisposed to CPM have inadequate energy provision as well as other factors that result in a pro-apoptotic drive, which renders them susceptible to brain injury from diverse causes. In CPM, the precipitant of brain injury appears to be osmotic stress. Furthermore, this model suggests a number of therapeutic interventions that may prevent or at least mitigate the consequences of CPM.

Oxidative stress, metabolism of ethanol and alcohol-related diseases

Alcohol-induced oxidative stress is linked to the metabolism of ethanol. Three metabolic pathways of ethanol have been described in the human body so far. They involve the following enzymes: alcohol dehydrogenase, microsomal ethanol oxidation system (MEOS) and catalase. Each of these pathways could produce free radicals which affect the antioxidant system. Ethanol per se, hyperlactacidemia and elevated NADH increase xanthine oxidase activity, which results in the production of superoxide. Lipid peroxidation and superoxide production correlate with the amount of cytochrome P450 2E1. MEOS aggravates the oxidative stress directly as well as indirectly by impairing the defense systems. Hydroxyethyl radicals are probably involved in the alkylation of hepatic proteins. Nitric oxide (NO) is one of the key factors contributing to the vessel wall homeostasis, an important mediator of the vascular tone and neuronal transduction, and has cytotoxic effects. Stable metabolites--nitrites and nitrates--were increased in alcoholics (34.3 +/- 2.6 vs. 22.7 +/- 1.2 micromol/l, p < 0.001). High NO concentration could be discussed for its excitotoxicity and may be linked to cytotoxicity in neurons, glia and myelin. Formation of NO has been linked to an increased preference for and tolerance to alcohol in recent studies. Increased NO biosynthesis also via inducible NO synthase (NOS, chronic stimulation) may contribute to platelet and endothelial dysfunctions. Comparison of chronically ethanol-fed rats and controls demonstrates that exposure to ethanol causes a decrease in NADPH diaphorase activity (neuronal NOS) in neurons and fibers of the cerebellar cortex and superior colliculus (stratum griseum superficiale and intermedium) in rats. These changes in the highly organized structure contribute to the motor disturbances, which are associated with alcohol abuse. Antiphospholipid antibodies (APA) in alcoholic patients seem to reflect membrane lesions, impairment of immunological reactivity, liver disease progression, and they correlate significantly with the disease severity. The low-density lipoprotein (LDL) oxidation is supposed to be one of the most important pathogenic mechanisms of atherogenesis, and antibodies against oxidized LDL (oxLDL) are some kind of epiphenomenon of this process. We studied IgG oxLDL and four APA (anticardiolipin, antiphosphatidylserine, antiphosphatidylethanolamine and antiphosphatidylcholine antibodies). The IgG oxLDL (406.4 +/- 52.5 vs. 499.9 +/- 52.5 mU/ml) was not affected in alcoholic patients, but oxLDL was higher (71.6 +/- 4.1 vs. 44.2 +/- 2.7 micromol/l, p < 0.001). The prevalence of studied APA in alcoholics with mildly affected liver function was higher than in controls, but not significantly. On the contrary, changes of autoantibodies to IgG oxLDL revealed a wide range of IgG oxLDL titers in a healthy population. These parameters do not appear to be very promising for the evaluation of the risk of atherosclerosis. Free radicals increase the oxidative modification of LDL. This is one of the most important mechanisms, which increases cardiovascular risk in chronic alcoholic patients. Important enzymatic antioxidant systems - superoxide dismutase and glutathione peroxidase - are decreased in alcoholics. We did not find any changes of serum retinol and tocopherol concentrations in alcoholics, and blood and plasma selenium and copper levels were unchanged as well. Only the zinc concentration was decreased in plasma. It could be related to the impairment of the immune system in alcoholics. Measurement of these parameters in blood compartments does not seem to indicate a possible organ, e.g. liver deficiency.

Blockade of alcohol-induced locomotor sensitization and conditioned place preference in DBA mice by 7-nitroindazole

Our previous studies indicated that inhibition or ablation of the neuronal nitric oxide synthase (nNOS) prevents the development of sensitization to the locomotor-stimulating effect of cocaine and cocaine-induced conditioned place preference (CPP). The present study was undertaken to investigate the effect of the nNOS inhibitor, 7-nitroindazole (7-NI), on ethanol-induced locomotor sensitization and CPP in DBA/2J mice. Administration of ethanol (1.5 g/kg; i.p.) for 7 days resulted in a progressive increase in the locomotor-stimulating effect of ethanol. Pretreatment with 7-NI (25 mg/kg) blocked the expression of the sensitized response to ethanol. A challenge injection of ethanol given 1 week and then 4 weeks following withdrawal from ethanol indicated that (a) ethanol sensitization was long lasting, and (b) the co-administration of 7-NI and ethanol attenuated the sensitized response to ethanol challenge. The CPP experiments showed that pairing four ethanol (2.5 g/kg) injections with a specific environment resulted in a marked preference for the drug-paired environment. The pretreatment with 7-NI (25 mg/kg) completely blocked ethanol-induced CPP. 7-NI alone produced neither rewarding nor aversive effects. Taken together, results of the present study indicate that blockade of nNOS by 7-NI-attenuated ethanol-induced behavioral sensitization and completely blocked the rewarding effect of ethanol. These findings support the role of NO in ethanol actions and further suggest that the nNOS system is relevant to the rewarding effects of various drugs of abuse.

Neuropsychiatric toxicity associated with cytokine therapies

The cytokines interleukin-2 and interferon-alpha are potent biological agents used to treat malignancy, infectious diseases, and neurodegenerative disorders. While these medications show substantial therapeutic promise, the neuropsychiatric toxicity associated with these agents is often treatment-limiting. The pathophysiology of this toxicity is not well delineated, and adverse effects to the central nervous system are often misdiagnosed by clinicians. This report reviews the preclinical and clinical literature describing the morbidity associated with these agents and suggests appropriate clinical management strategies and future directions for research.