Interaction Between Alcohol and Nitric Oxide on ACTH Release in the Rat

Oral administration of resveratrol reduces oxidative stress generated in the hippocampus of Wistar rats in response to consumption of ethanol

Introduction

Chronic ethanol intake has been found to favor hippocampal deterioration and alter neuronal morphological maturation; resveratrol has been suggested as an antioxidant that may counteract these effects. The objective of this study was to analyze the effect of resveratrol on oxidative stress markers, endogenous antioxidant system in the hippocampus, and the behavior of male Wistar rats administered different concentrations of ethanol.

Methods

The animals, at 3 months old, were randomly distributed into 11 study groups (n = 6/group), orally administered (5 days on, 2 days off) with water (control), ethanol (10, 20, 30, 40 or 50%), or ethanol (10, 20, 30, 40 or 50%) plus resveratrol (10 mg/Kg/day) for 2 months. Subsequently, the production of nitrites, malondialdehyde, and 4-hydroxy-alkenal (HNE) and the enzymatic activity of catalase and superoxide dismutase (SOD) were quantified.

Results

The levels of nitric oxide and lipid peroxidation products were significantly increased in each ethanol concentration and were statistically different compared to the control group; however, resveratrol significantly reduced oxidative stress caused by high ethanol concentration. The SOD and CAT did not present significant changes with respect to the controls in any of the study groups. In the different concentrations of ethanol used, GR increases significantly in the groups administered with resveratrol but not GPx. Resveratrol was shown to maintain the results similar to the control at most ethanol concentrations.

Discussion

Our results suggest that resveratrol prevents oxidative stress induced by ethanol in the hippocampus by decreasing cellular lipid peroxidation, but does not prevent the activation of catalase or SOD enzymes; however, allows glutathione to be kept active and in adequate concentrations in its reduced form and avoids alterations in the locomotor system.

D-ribose-L-cysteine exhibits neuroprotective activity through inhibition of oxido-behavioral dysfunctions and modulated activities of neurotransmitters in the cerebellum of Juvenile mice exposed to ethanol

Alcohol exposure to the cerebellum has been known to trigger cerebellar dysfunctions through several mechanisms. This present study was designed to evaluate the repealing effect of D-ribose-L-cysteine (DRLC) on alcohol-induced cerebellar dysfunctions in juvenile BALB/c mice. The animals were randomly divided into 4 groups (n = 10 per group). Mice were given oral administration of normal saline (control), DRLC (100 mg/kg, p.o), ethanol (0.2 mL of 10% w/v), or DRLC (100 mg/kg, p.o) + ethanol (0.2 mL of 10% w/v). On day 29 of the study (i.e., 24 h after the administration of the last respective doses), neurochemical quantification of the respective levels of serotonin and dopamine, lipid peroxidation, total antioxidant, superoxide dismutase, and glutathione peroxidase in the cerebellar tissues of the mice were analyzed. Compared with the saline-treated group, the studied neurochemical indices were modulated across the various experimental groups. The administration of ethanol significantly modulates the levels of monoamine neurotransmitters (serotonin and dopamine) as well as contents of total antioxidants, activities of superoxide dismutase, and glutathione peroxidase, with a concurrently increased level of lipid peroxidase in the cerebellar tissue of the mice. DRLC significantly reverses these effects in the DRLC + ethanol co-treated group. Combined exposure to DRLC + ethanol counteracts the deleterious effect of ethanol in the cerebellum of juvenile BALB/c mice via monoamine neurotransmitter, lipid peroxidation, total antioxidant status, superoxide dismutase, and glutathione peroxidase action pathways. Therefore, DRLC could be a pharmacologic or therapeutic agent in attenuating the deleterious effects of alcohol on the cerebellum.

Exposure to alcohol during adolescence exerts long-term effects on stress response and the adult brain stress circuits

The hypothalamic-pituitary-adrenal (HPA) axis undergoes critical developments during adolescence. Therefore, stressors experienced during this period potentially have long-term effects on adult HPA axis function. We hypothesized that adolescent intermittent ethanol (AIE) exposure would affect adult HPA axis function, resulting in altered responses to an alcohol challenge in young adults or adults. To test these hypotheses, male rats were exposed to alcohol vapor for 6h per day from post-natal day (PND) 28-42, then acutely challenged with alcohol intragastrically (3.2-4.5g/kg) in young adults (PND 70) or adults (PND 90). Overall, we observed blunted HPA axis responses to an alcohol challenge due to AIE exposure. Specifically, AIE tended to inhibit the alcohol challenge-induced increase in plasma corticosterone (CORT) concentrations in young adult and adult rats. As well, AIE significantly blunted the alcohol challenge-induced arginine vasopressin (Avp) mRNA expression in the paraventricular nucleus (PVN) of the hypothalamus of adult rats. Results of the present study are similar to what we have previously shown, that these changes in PVN responsiveness may result from AIE-induced alterations in adrenergic neurons in brain stem regions C1-C3 known to project to the PVN. AIE elevated the number of colocalized c-fos/phenylethanolamine N-methyltransferase (PNMT)-positive cell bodies in the C1 region of adult rats. Together, these data suggest that AIE exposure produces alterations in male HPA axis responsiveness to administration of an acute alcohol challenge that may be long-lasting.

Role of hypothalamic corticotropin-releasing factor in mediating alcohol-induced activation of the rat hypothalamic-pituitary-adrenal axis

Alcohol stimulates the hypothalamic-pituitary-adrenal (HPA) axis through brain-based mechanisms in which endogenous corticotropin-releasing factor (CRF) plays a major role. This review first discusses the evidence for this role, as well as the possible importance of intermediates such as vasopressin, nitric oxide and catecholamines. We then illustrate the long-term influence exerted by alcohol on the HPA axis, such as the ability of a first exposure to this drug during adolescence, to permanently blunt neuroendocrine responses to subsequent exposure of the drug. In view of the role played by CRF in addiction, it is likely that a better understanding of the mechanisms through which this drug stimulates the HPA axis may lead to the development of new therapies used in the treatment of alcohol abuse, including clinically relevant CRF antagonists.

Alcohol abuse and the injured host: dysregulation of counterregulatory mechanisms review

Traumatic injury ranks as the number one cause of death for the younger than 44 years age group and fifth leading cause of death overall (www.nationaltraumainstitute.org/home/trauma_statistics.html). Although improved resuscitation of trauma patients has dramatically reduced immediate mortality from hemorrhagic shock, long-term morbidity and mortality continue to be unacceptably high during the postresuscitation period particularly as a result of impaired host immune responses to subsequent challenges such as surgery or infection. Acute alcohol intoxication (AAI) is a significant risk factor for traumatic injury, with intoxicating blood alcohol levels present in more than 40% of injured patients. Severity of trauma, hemorrhagic shock, and injury is higher in intoxicated individuals than that of sober victims, resulting in higher mortality rates in this patient population. Necessary invasive procedures (surgery, anesthesia) and subsequent challenges (infection) that intoxicated trauma victims are frequently subjected to are additional stresses to an already compromised inflammatory and neuroendocrine milieu and further contribute to their morbidity and mortality. Thus, dissecting the dynamic imbalance produced by AAI during trauma is of critical relevance for a significant proportion of injured victims. This review outlines how AAI at the time of hemorrhagic shock not only prevents adequate responses to fluid resuscitation but also impairs the ability of the host to overcome a secondary infection. Moreover, it discusses the neuroendocrine mechanisms underlying alcohol-induced hemodynamic dysregulation and its relevance to host defense restoration of homeostasis after injury.

Adolescent alcohol exposure alters the rat adult hypothalamic-pituitary-adrenal axis responsiveness in a sex-specific manner

Exposure to alcohol during adolescence exerts long-term effects on the adult brain stress circuits, causing many changes that persist into adulthood. Here we examined the consequences of adolescent intermittent ethanol (AIE, administered from postnatal day (PND) 28-42) on the hypothalamic-pituitary-adrenal (HPA) axis-related brain circuitry of rats challenged with intragastric (ig) administration of alcohol in adulthood (PND 70-71). Both male and female adolescent rats were exposed to alcohol vapors, while controls did not receive the drug, to assess whether AIE alters adult alcohol response in a sex-specific manner. We demonstrated that AIE increased paraventricular nucleus (PVN) Avp mRNA levels during late (PND 42) but not middle (PND 36) adolescence in males. While an alcohol challenge administered to 70-71-day-old rats increased Crf mRNA levels in males and Avp mRNA levels in females, AIE blunted both effects. These results suggest that AIE produced long-lasting changes in the responsiveness of the HPA axis to a subsequent alcohol challenge in a sex-specific manner. Furthermore, AIE altered adrenergic brain stem nuclei involved in stress responses in adulthood, resulting in increased numbers of phenylethanolamine N-methyltransferase (PNMT) neurons in male C2 and female C1 regions. This tended to enhance activation of the male C2 nucleus upon alcohol challenge. Collectively, these results suggest that AIE exerts long-term effects on the ability of the PVN to respond to an alcohol challenge in adulthood, possibly mediated by catecholaminergic input from the brain stem to the PVN.

Neuronal nitric oxide synthase mediates the effect of ethanol on IgA

AIMS

We showed previously that the acute effect of ethanol on intestinal immunoglobulin A (IgA) expression might be mediated by endogenous nitric oxide (NO). To extend these findings, this study was designed to investigate a possible role of neuronal NO synthase (nNOS) in the observed phenomenon, using 7-nitroindazole (7-NI), a selective inhibitor of its activity.

METHODS

Adult male Wistar rats were treated with: (a) ethanol (4 g/kg, intraperitoneally, i.p.), (b) 7-NI (25 mg/kg, i.p.) followed by ethanol (4 g/kg, i.p.) 30 min later and (c) 7-NI (25 mg/kg, i.p.) followed by saline 30 min later. Untreated rats were used as controls. The concentrations of serum and intestinal IgA were measured by enzyme-linked immunosorbent assay, while the expression of nNOS was determined using western blot and immunohistochemistry.

RESULTS

Acute ethanol treatment significantly increased the concentration of IgA in the ileal extracts, whereas it decreased its serum level. Inhibition of nNOS activity by 7-NI abolished this action of alcohol on IgA. Additionally, western blot analysis revealed that the acute alcohol administration induced an increase in the expression of intestinal nNOS. Furthermore, nNOS-immunoreactive cells, observed within the lamina propria of small intestine, were numerous in ethanol-treated rats.

CONCLUSION

Taken together, these results extended our previous findings suggesting that nNOS mediates the acute effect of ethanol on IgA and supported an immunomodulatory role of this enzyme isoform.

Alcohol and inflammation and infection: clinical and experimental systems--summary of the 2010 Alcohol and Immunology Research Interest Group Meeting

The 15th annual meeting of the Alcohol and Immunology Research Interest Group was held on November 19, 2010, at Loyola University Medical Center in Maywood, IL. This year, the focus of the meeting was on alcohol's effect on the immune system in both clinical and experimental systems. The event consisted of three sessions, which featured plenary talks from invited speakers along with oral presentations from selected abstracts, in addition to a poster session. Participants presented a variety of information on ethanol-induced effects on infection susceptibility and resolution, oxidative stress, and organ inflammation. Specifically, speakers presented new insights on the mechanism of alcohol-mediated deleterious effects in the lung, liver, skin, and neuroendocrine system, as well as on immune cells in both in vivo and in vitro systems. Additional oral presentations suggested possible mechanisms of how alcohol-induced reactive oxygen species promote immune dysregulation both locally and systemically.

Augmented central nitric oxide production inhibits vasopressin release during hemorrhage in acute alcohol-intoxicated rodents

Acute alcohol intoxication (AAI) attenuates the AVP response to hemorrhage, contributing to impaired hemodynamic counter-regulation. This can be restored by central cholinergic stimulation, implicating disrupted signaling regulating AVP release. AVP is released in response to hemorrhage and hyperosmolality. Studies have demonstrated nitric oxide (NO) to play an inhibitory role on AVP release. AAI has been shown to increase NO content in the paraventricular nucleus. We hypothesized that the attenuated AVP response to hemorrhage during AAI is the result of increased central NO inhibition. In addition, we predicted that the increased NO tone during AAI would impair the AVP response to hyperosmolality. Conscious male Sprague-Dawley rats (300-325 g) received a 15-h intragastric infusion of alcohol (2.5 g/kg + 300 mg·kg(-1)·h(-1)) or dextrose prior to a 60-min fixed-pressure hemorrhage (∼40 mmHg) or 5% hypertonic saline infusion (0.05 ml·kg(-1)·min(-1)). AAI attenuated the AVP response to hemorrhage, which was associated with increased paraventricular NO content. In contrast, AAI did not impair the AVP response to hyperosmolality. This was accompanied by decreased paraventricular NO content. To confirm the role of NO in the alcohol-induced inhibition of AVP release during hemorrhage, the nitric oxide synthase inhibitor, nitro-l-arginine methyl ester (l-NAME; 250 μg/5 μl), was administered centrally prior to hemorrhage. l-NAME did not further increase AVP levels during hemorrhage in dextrose-treated animals; however, it restored the AVP response during AAI. These results indicate that AAI impairs the AVP response to hemorrhage, while not affecting the response to hyperosmolality. Furthermore, these data demonstrate that the attenuated AVP response to hemorrhage is the result of augmented central NO inhibition.

Immediate and prolonged effects of alcohol exposure on the activity of the hypothalamic-pituitary-adrenal axis in adult and adolescent rats

Alcohol stimulates the hypothalamic-pituitary-adrenal (HPA) axis. Part of this influence is likely exerted directly at the level of the corticotropin-releasing factor (CRF) gene, but intermediates may also play a role. Here we review the effect of alcohol on this axis, provide new data on the effects of binge drinking during adolescence, and argue for a role of catecholaminergic circuits. Indeed, acute injection of this drug activates brain stem adrenergic and noradrenergic circuits, and their lesion, or blockade of α1 adrenergic receptors significantly blunts alcohol-induced ACTH release. As alcohol can influence the HPA axis even once discontinued, and alcohol consumption in young people is associated with increased adult drug abuse (a phenomenon possibly mediated by the HPA axis), we determined whether alcohol consumption during adolescence modified this axis. The number of CRF-immunoreactive (ir) cells/section was significantly decreased in the central nucleus of the amygdala of adolescent self-administering binge-drinking animals, compared to controls. When another group of adolescent binge-drinking rats was administered alcohol in adulthood, the number of colocalized c-fos-ir and PNMT-ir cells/brain stem section in the C3 area was significantly decreased, compared to controls. As the HPA axis response to alcohol is blunted in adult rats exposed to alcohol vapors during adolescence, a phenomenon which was not observed in our model of self-administration, it is possible that the blood alcohol levels achieved in various models play a role in the long-term consequences of exposure to alcohol early in life. Collectively, these results suggest an important role of brain catecholamines in modulating the short- and long-term consequences of alcohol administration.

Brain stem catecholamines circuitry: activation by alcohol and role in the hypothalamic-pituitary-adrenal response to this drug

Although the stimulatory effect of alcohol on the rat hypothalamic-pituitary-adrenal (HPA) axis is well known, the mechanisms underlying this influence remain poorly understood. In the present study, we tested the hypothesis that brain catecholamines play an important role in this response. As expected, the acute intragastric administration of alcohol to adult male rats elevated plasma adrenocorticotrophic hormone (ACTH) levels and activated hypothalamic corticotrophin-releasing factor neurones. Novel findings pertain to the effect of alcohol on, and the role played by, brain adrenergic circuits. We first observed that alcohol up-regulated c-fos signals in the locus coeruleus, the main noradrenergic brain cell group; and that it activated (nor)adrenergic medullary cells (A1-A2/C1-C3). Evidence for the role played by these catecholaminergic circuits then came from the observation that blockade of α(1) -, but not β-, adrenergic receptors interfered with alcohol-induced ACTH secretion; and that depletion of catecholaminergic input to the paraventricular nucleus (PVN) by the toxin 6-hydroxydopamine significantly decreased the ACTH response to alcohol. Finally, destruction of the A1-A2/C1-C3 region with the immunotoxin anti-dopamine-B-hydroxylase-saporin interfered with the catecholaminergic input to the PVN. Collectively, our work extends our knowledge of the ability of this drug to up-regulate catecholamine circuitry in the rat brain. It also shows that medullary catecholamine innervation of the hypothalamus plays an important role in modulating the stimulatory effect of alcohol on the HPA axis, an effect exerted through activation of α(1) -adrenergic receptors.

Adolescent alcohol exposure alters the central brain circuits known to regulate the stress response

Adolescent alcohol exposure (AAE) may exert long-term effects on the adult brain. Here, we tested the hypothesis that the brain regions affected include the rat hypothalamic-pituitary-adrenal (HPA) axis. Specifically, we examined the consequences of AAE [postnatal days (PND) 28-42] on the HPA axis-related brain circuitry of male rats challenged with an intragastric (ig) administration of alcohol in young adulthood (PND 61-62). Adolescent rats were exposed to alcohol vapors, while controls did not receive the drug. The mean blood alcohol level in adolescence on PND 40 was 212.8±5.7 mg %. Using immunohistochemistry and in situ hybridization procedures, we measured signals for c-fos and corticotropin releasing factor (CRF) in the paraventricular nucleus (PVN) of the hypothalamus, as well as signals for c-fos and phenylethanolamine N-methyltransferase (PNMT) in the adrenergic brain stem regions (C1 and C2). PVN CRF mRNA expression was significantly blunted in AAE rats tested at PND 61-62, compared to their controls. These animals also displayed a significant increase in the mean number of PNMT-ir cells/brain stem section in the C2 area. Collectively, these results suggest that exposure to alcohol vapors during adolescence exerts long-term effects on the ability of the PVN to mount a response to an acute alcohol administration in young adulthood, possibly mediated by medullary catecholamine input to the PVN.

The role of nicotinic acetylcholine receptor (nAChR) α7 subtype in the functional interaction between nicotine and ethanol in mouse cerebellum

BACKGROUND

Many epidemiological studies report that alcoholics overwhelmingly smoke tobacco and vice versa, which suggests a possible functional interaction between ethanol and nicotine. Although nicotine-ethanol interaction is well documented within the central nervous system, the mechanism is not well understood. Therefore, it is important from a public health standpoint to understand the mechanisms involved in nicotine and ethanol functional interaction. The intracerebellar (ICB) administration of nicotine significantly attenuates ethanol ataxia through nicotinic acetylcholine receptor (nAChR) α(4)β(2) subtype. This study, an extension of earlier work, was intended to investigate the possible role of nAChR subtype α(7) in mitigating ethanol ataxia.

METHODS

The effect of ICB injection of PNU-282987 (α(7) agonist; 25 ng to 2.5 μg) and the antagonist methyllycaconitine was evaluated on ethanol (2 g/kg; i.p.)-induced ataxia with a Rotorod. Cerebellar nitric oxide was determined fluorometrically in the presence of ethanol and/or PNU-282987.

RESULTS

Attenuation of ethanol-induced ataxia following PNU-282987 microinfusion was dose-dependent suggesting the participation of α(7) subtype in nicotine and ethanol interaction. Intracerebellar pretreatment with methyllycaconitine (α(7) -selective antagonist; 6 ng) virtually abolished the attenuating effect of PNU-282987 as well as the effect of nicotine, but not of RJR-2403 (α(4)β(2) -selective agonist; 125 ng) on ethanol-induced ataxia. Finally, ethanol administration significantly decreased cerebellar NO(x), whereas ICB PNU-282987 significantly increased and/or opposed ethanol-induced decrease in NO(x). These results were functionally in agreement with our Rotorod data.

CONCLUSIONS

These observations confirmed the following: (i) α(7) participation in nicotine-ethanol interaction and (ii) α(7) selectivity of methyllycaconitine. Overall, the results demonstrate the role of cerebellar nAChR α(7) subtype in nicotine-induced attenuation of ethanol-induced ataxia in cerebellar NO(x)-sensitive manner.

Role of mouse cerebellar nicotinic acetylcholine receptor (nAChR) α(4)β(2)- and α(7) subtypes in the behavioral cross-tolerance between nicotine and ethanol-induced ataxia

We have demonstrated that nicotine attenuated ethanol-induced ataxia via nicotinic-acetylcholine-receptor (nAChR) subtypes α(4)β(2) and α(7). In the present study, ethanol (2g/kg; i.p.)-induced ataxia was assessed by Rotorod performance following repeated intracerebellar infusion of α(4)β(2)- and α(7)-selective agonists. Localization of α(4)β(2) and α(7) nAChRs was confirmed immunohistochemically. Cerebellar NO(x) (nitrite+nitrate) was determined flurometrically. Repeated intracerebellar microinfusion of the α(4)β(2)-selective agonist, RJR-2403 (for 1, 2, 3, 5 or 7 days) or the α(7)-selective agonist, PNU-282987 (1, 2, 3 or 5 days), dose-dependently attenuated ethanol-induced ataxia. These results suggest the development of cross-tolerance between ethanol-induced ataxia and α(4)β(2) and α(7) nAChR agonists. With RJR-2403, the cross-tolerance was maximal after a 5-day treatment and lasted 48h. Cross-tolerance was maximal after a 1-day treatment with PNU-282987 and lasted 72h. Pretreatment with α(4)β(2)- and α(7)-selective antagonists, dihydro-β-erythroidine and methyllycaconitine, respectively, prevented the development of cross-tolerance confirming α(4)β(2) and α(7) involvement. Repeated agonist infusions elevated cerebellar NO(x) 16h after the last treatment while acute ethanol exposure decreased it. Pretreatment with repeated RJR-2403 or PNU-282987 reversed ethanol-induced decrease in NOx. The NO(x) data suggests the involvement of the nitric oxide (NO)-cGMP signaling pathway in the cross-tolerance that develops between α(4)β(2)- and α(7)-selective agonists and ethanol ataxia. Both α(4)β(2) and α(7) subtypes exhibited high immunoreactivity in Purkinje but sparse expression in molecular and granular cell layers. Our results support a role for α(4)β(2) and α(7) nAChR subtypes in the development of cross-tolerance between nicotine and ethanol with the NO signaling pathway as a potential mechanism.

Long-lasting reduction in hippocampal neurogenesis by alcohol consumption in adolescent nonhuman primates

Binge alcohol consumption in adolescents is increasing, and studies in animal models show that adolescence is a period of high vulnerability to brain insults. The purpose of the present study was to determine the deleterious effects of binge alcohol on hippocampal neurogenesis in adolescent nonhuman primates. Heavy binge alcohol consumption over 11 mo dramatically and persistently decreased hippocampal proliferation and neurogenesis. Combinatorial analysis revealed distinct, actively dividing hippocampal neural progenitor cell types in the subgranular zone of the dentate gyrus that were in transition from stem-like radial glia-like cells (type 1) to immature transiently amplifying neuroblasts (type 2a, type 2b, and type 3), suggesting the evolutionary conservation of milestones of neuronal development in macaque monkeys. Alcohol significantly decreased the number of actively dividing type 1, 2a, and 2b cell types without significantly altering the early neuronal type 3 cells, suggesting that alcohol interferes with the division and migration of hippocampal preneuronal progenitors. Furthermore, the lasting alcohol-induced reduction in hippocampal neurogenesis paralleled an increase in neural degeneration mediated by nonapoptotic pathways. Altogether, these results demonstrate that the hippocampal neurogenic niche during adolescence is highly vulnerable to alcohol and that alcohol decreases neuronal turnover in adolescent nonhuman primate hippocampus by altering the ongoing process of neuronal development. This lasting effect, observed 2 mo after alcohol discontinuation, may underlie the deficits in hippocampus-associated cognitive tasks that are observed in alcoholics.

Alcohol induced region-dependent alterations of hemodynamic response: implications for the statistical interpretation of pharmacological fMRI studies

Worldwide, ethanol abuse causes thousands of fatal accidents annually as well as innumerable social dysfunctions and severe medical disorders. Yet, few studies have used the blood oxygenation level dependent functional magnetic resonance imaging method (BOLD fMRI) to map how alcohol alters brain functions, as fMRI relies on neurovascular coupling, which may change due to the vasoactive properties of alcohol. We monitored the hemodynamic response function (HRF) with a high temporal resolution. In both motor cortices and the visual cortex, alcohol prolonged the time course of the HRF, indicating an overall slow-down of neurovascular coupling rather than an isolated reduction in neuronal activity. However, in the supplementary motor area, alcohol-induced changes to the HRF suggest a reduced neuronal activation. This may explain why initiating and coordinating complex movements, including speech production, are often impaired earlier than executing basic motor patterns. Furthermore, the present study revealed a potential pitfall associated with the statistical interpretation of pharmacological fMRI studies based on the general linear model: if the functional form of the HRF is changed between the conditions data may be erroneously interpreted as increased or decreased neuronal activation. Thus, our study not only presents an additional key to how alcohol affects the network of brain functions but also implies that potential changes to neurovascular coupling have to be taken into account when interpreting BOLD fMRI. Therefore, measuring individual drug-induced HRF changes is recommended for pharmacological fMRI.

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.

Behavioral Cross-Tolerance between Repeated Intracerebellar Nicotine and Acute Δ9-Tetrahydrocannabinol-Induced Cerebellar Ataxia: Role of Cerebellar Nitric Oxide

We have previously demonstrated that acute intracerebellar nicotine or N-methyl-4-(3-pyridinyl)-3-buten-1-amine (RJR-2403), a selective alpha(4)beta(2) nicotinic acetylcholine receptor (nAChR) agonist, dose dependently attenuates Delta(9)-tetrahydrocannabinol (Delta(9)THC)-induced ataxia. Presently, we have shown that intracerebellar nicotine (1.25, 2.5, and 5 ng; once daily for 5 days) and RJR-2403 (250, 500, and 750 ng; once daily for 5 days) significantly attenuate cerebellar Delta(9)-THC-induced ataxia dose dependently, suggesting the development of cross-tolerance between nicotine or RJR-2403 with Delta(9)-THC in male CD-1 mice. Intracerebellar RJR-2403 (750 ng) microinfused for 1, 2, 3, 5, and 7 days (once daily) significantly attenuated Delta(9)-THC-induced ataxia in the 3-, 5-, and 7-day treatment groups; optimal cross-tolerance was evident at day 5 and persisted till 36 h after the last RJR-2403 microinfusion. Intracerebellar microinfusion of hexamethonium (nAChR antagonist; 1 microg) or dihydro-beta-erythroidine hydrobromide (alpha(4)beta(2) nAChR antagonist; 500 ng) for 5 days 10 min before daily intracerebellar nicotine or RJR-2403 microinfusion virtually abolished cross-tolerance between nicotine or RJR-2403 and Delta(9)-THC, indicating nAChR participation. In addition, microinfusion of antagonists 10 min after daily intracerebellar nicotine or RJR-2403 failed to alter the cross-tolerance, suggesting possible involvement of downstream cerebellar second-messenger mechanisms. Finally, the cerebellar concentration of nitric oxide products [total sum of nitrite + nitrate (NO(x))] was increased after 5 days of intracerebellar nicotine or RJR-2403 treatment, which was decreased by acute intracerebellar Delta(9)-THC treatment. The "nicotine or RJR-2403 + Delta(9)-THC" treatments significantly increased cerebellar NO(x) levels compared with treatment with Delta(9)-THC alone, supporting a functional correlation between cerebellar nitric oxide production and cerebellar Delta(9)-THC-induced ataxia and suggesting participation of nitric oxide in the observed cross-tolerance between nicotine/RJR-2403 and Delta(9)-THC.

Involvement of the alpha4beta2 nicotinic receptor subtype in nicotine-induced attenuation of delta9-THC cerebellar ataxia: role of cerebellar nitric oxide

We have recently reported that mediation of intracerebellar nicotine-induced attenuation of cerebellar delta9-THC ataxia was via the alpha4beta2 nAChR. The present study was meant to investigate the role of cerebellar nitric oxide (NO)-guanylyl cyclase (GC) signaling in the alpha4beta2-mediated attenuation in CD-1 male mice. Drugs were given via intracerebellar microinfusion using stereotaxically implanted guide cannulas, with ataxia evaluated by Rotorod. Intracerebellar microinfusion of SNP (sodium nitroprusside, NO donor; 15, 30, 60 pg) and SMT (S-methylisothiourea, inhibitor of inducible NO synthase; 70, 140, 280 fg) significantly enhanced and reduced, respectively, intracerebellar RJR-2403 (selective alpha4beta2 agonist)-induced attenuation of delta9-THC ataxia dose-dependently. Intracerebellar isoliquiritigenin (GC-activator; 1, 2, 4 pg) and ODQ (1H[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one, GC inhibitor; 200, 400, 800 fg), significantly enhanced and reduced, respectively, intracerebellar RJR-2403-induced attenuation of delta9-THC ataxia dose-dependently. Further support for the role of NO was evidenced via increases in cerebellar NO(x) (nitrate+nitrite) levels following microinfusion of nicotine or RJR-2403 as compared to control, whereas delta9-THC significantly decreased NO(x) levels. "Nicotine/RJR-2403+delta9-THC" treated mice had cerebellar NO(x) levels significantly increased as compared to mice infused with delta9-THC alone. Results of the present investigation support the role of cerebellar NO-GC signaling in alpha4beta2 nAChR subtype-mediated attenuation of delta9-THC ataxia.

A low chronic ethanol exposure induces morphological changes in the adolescent rat brain that are not fully recovered even after a long abstinence: An immunohistochemical study

Little is known about the morphological effects of alcoholism on the developing adolescent brain and its consequences into adulthood. We studied here the relationship between two neurotransmitter systems (the serotoninergic and nitrergic) and the astrocytic and neuronal cytoskeleton immediately and long after drinking cessation of a chronic, but low, ethanol administration. Adolescent male Wistar rats were exposed to ethanol 6.6% (v/v) in drinking water for 6 weeks and studied after ending exposure or after a 10-week recovery period drinking water. Control animals received water. Brain sections were processed by immunohistochemistry using antibodies to serotonin (5-HT); glial fibrillary acidic protein (GFAP); astroglial S-100b protein; microtubule associated protein-2 (MAP-2); 200 kDa neurofilaments (Nf-200); and neuronal nitric oxide synthase (nNOS). The mesencephalic dorsal and median raphe nucleus (DRN; MRN) and three prosencephalic areas closely related to cognitive abilities (CA1 hippocampal area, striatum and frontal cortex) were studied by digital image analysis. 5-HT immunoreactivity (-ir) decreased in the DRN and recovered after abstinence and was not changed in the MRN. In the three prosencephalic areas, astrocytes' cell area (GFAP-ir cells) increased after EtOH exposure and tended to return to normality after abstinence, while cytoplasmic astroglial S100b protein-ir, relative area of MAP-2-ir and Nf-200-ir fibers decreased, and later partially recovered. In the striatum and frontal cortex, nNOS-ir decreased only after abstinence. In conclusion, in the adolescent brain, drinking cessation can partially ameliorate the ethanol-induced morphological changes on neurons and astrocytes but cannot fully return it to the basal state.

Possible role of mouse cerebellar nitric oxide in the behavioral interaction between chronic intracerebellar nicotine and acute ethanol administration: Observation of cross-tolerance

Many studies have reported cross-tolerance between nicotine and ethanol. Previously we demonstrated that intracerebellar nicotine attenuates ethanol-induced motor impairment. In this study, intracerebellar nicotine (0.625, 2.5, 5 ng; once daily for five days) significantly attenuated ethanol-induced motor impairment in a dose-dependent fashion suggesting the development of cross-tolerance between nicotine and ethanol in male CD-1 mice. Using the same paradigm, intracerebellar nicotine (5 ng) microinfused for 1, 2, 3, 5, 7 days significantly attenuated ethanol-induced motor impairment in all groups except the 1-day treatment group. Cross-tolerance, which developed optimally in 5-day nicotine treatment group, was reversible and detectable up to 40 h post-nicotine microinfusion. Intracerebellar microinfusion of hexamethonium (1 mug once daily for 5 days): (i) did not alter ethanol-induced motor impairment indicating no tonic nicotine receptor involvement; (ii) 10 min prior to daily intracerebellar nicotine treatment virtually abolished the cross-tolerance between nicotine and ethanol indicating nicotinic acetylcholine receptor participation; (iii) when microinfused 10 min after daily intracerebellar nicotine treatment, failed to abolish the cross-tolerance which suggested possible participation of downstream second messenger mechanisms. Chronic intracerebellar microinfusion of nicotine: (i) failed to attenuate acute pentobarbital (25mg/kg i.p.)-induced motor impairment; and (ii) produced no change in normal motor coordination when followed by saline injection. Finally, the cerebellar concentration of total nitric oxide products (nitrite+nitrate; NO(x)); (i) was increased after 5-day intracerebellar nicotine; (ii) was decreased by acute ethanol administration; and (iii) decreased due to acute ethanol administration which was opposed by chronic intracerebellar nicotine treatment. These results support a functional correlation between the cerebellar nitric oxide production and ethanol-induced motor impairment and suggest possible participation of nitric oxide as a factor in the observed cross-tolerance between nicotine and ethanol.

Antagonism of ethanol ataxia by intracerebellar nicotine: possible modulation by mouse cerebellar nitric oxide and cGMP

We have reported previously that intracerebellar nicotine attenuates ethanol ataxia via nicotinic-cholinergic receptors. We report now that attenuation of ethanol ataxia by intracerebellar nicotine is modulated by cerebellar nitric oxide-guanylyl cyclase (GC) messenger system. Intracerebellar microinfusion of SNP (sodium nitroprusside, a nitric oxide donor; 15, 30, and 60 pg) and SMT (S-methylisothiourea; 70, 140, and 280 fg; an inhibitor of inducible nitric oxide synthase), significantly enhanced and reduced, respectively, intracerebellar nicotine-induced attenuation of ethanol ataxia in a dose-related manner. Similarly, intracerebellar isoliquiritigenin (an activator of GC; 1, 2, and 4 pg) and ODQ (1H [1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one, an inhibitor of GC; 375, 750, and 1500 fg), significantly enhanced and reduced, respectively, intracerebellar nicotine-induced attenuation of ethanol ataxia in a dose-related fashion. These results suggest that the functional interaction between nicotine and ethanol may involve modulation by cerebellar nitric oxide and cGMP. Intracerebellar microinfusion of isoliquiritigenin (4, 8, and 16 pg) in the absence of nicotine significantly attenuated ethanol ataxia dose-dependently indicating a tonic involvement of cGMP in ethanol ataxia. Finally, intracerebellar nicotine (5 ng) significantly increased and ethanol 2 g/kg i.p. decreased levels of total cerebellar nitrite+nitrate (NOx) which were functionally correlated with ethanol ataxia and its attenuation by intracerebellar nicotine. The ethanol-induced decrease in NOx was significantly antagonized by intracerebellar nicotine. The NOx data further supported an involvement of nitric oxide in the behavioral interaction between nicotine and ethanol. Overall, the results of the present investigation demonstrate a functional correlation between cerebellar nitric oxide messenger system and the behavioral interaction between nicotine and ethanol.

Interactions of alcohol and nitric-oxide synthase in the brain

Nitric oxide (NO) is an important molecule associated with both physiological and pathological brain events. Three separate genes encode for nitric-oxide synthase (NOS), the rate-limiting enzyme in NO production, all of which are expressed within brain tissue. Effects of ethanol on NO production may be important to ethanol modification of brain function. Existing data indicate that alcohol exposure alters NOS expression and activity in the brain. Modulation of NOS is suggested to be involved in alcohol-induced behavioral modifications. Furthermore, alcohol-induced changes in NOS may alter immunocompetence, response to injury in the central nervous system, and may be involved in ethanol-mediated neurodegeneration and neurotoxicity. The extent and direction of change in NOS expression and activity depends on cell type and length of exposure. The mechanisms underlying these effects are only partially understood. Herein, the current understanding of the interactions of ethanol and NOS in the brain are discussed.

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.

Involvement of non-exocytotic mechanisms in ethanol-induced in vivo dopamine release: comparisons with cocaine

In order to determine whether a non-exocytotic mechanism was involved in ethanol-induced in vivo dopamine release in the nucleus accumbens, extracellular dopamine concentrations were measured via intracerebral microdialysis in freely moving Sprague-Dawley rats. Effects of ethanol on dopamine release in the nucleus accumbens were compared with those by cocaine, a drug that increases synaptic dopamine by a mechanism, which depends on neuronal activity and involves an exocytotic process. Administration of ethanol (80 mM) or cocaine (10 microM) via a dialysis probe increased extracellular dopamine concentrations in the nucleus accumbens. Pretreatments with tetrodotoxin (2 microM) or Ca2+ withdrawal did not block the ability of ethanol to increase nucleus accumbens dopamine. The blockade of dopamine autoreceptors by local infusion of sulpiride did not significantly alter the effect of ethanol on nucleus accumbens dopamine either. As opposed to ethanol, however, cocaine-induced increases in nucleus accumbens dopamine were sensitive to tetrodotoxin or Ca2+ omission. In addition, pretreatments with sulpiride significantly potentiated the effect of cocaine on extracellular dopamine concentrations. These differences in responses to tetrodotoxin, Ca2+ withdrawal and inhibition of dopamine autoreceptors suggest that a non-exocytotic mechanism may be involved in dopamine release in the nucleus accumbens evoked by focally applied ethanol.