Ethanol Intake In Wistar Rats Research Articles

Mental nerve injury induces novelty seeking behaviour leading to increasing ethanol intake in Wistar rats

ObjectiveDental treatment and orofacial surgeries may induce chronic neuropathic orofacial pain (CNOP). This kind of pain affects adaptability to environmental changes in both model animals and humans. Part of the adaptation process depends on the ability to distinguish between familiar and novel stimuli. CNOP induces novelty seeking behaviour as a deficit in environmental adaptation. Alternatively, novelty seeking is a sign for susceptibility to the development of substance abuse. Evidence shows that CNOP leads to alcoholism in animal models. The behavioural relationship between CNOP, novelty seeking behaviour and substance abuse is unknown. In this article, we investigate if CNOP produces an increase in novelty seeking and leads to increasing ethanol intake. DesignFirstly, we used mental nerve injury as a neuropathic orofacial pain model to evaluate both thermal and mechanical allodynia. We used the novel recognition task to determine novelty seeking behaviour and the drink in darkness protocol to assess ethanol intake. ResultsOur results show that mental nerve constriction increases novelty seeking behaviour (p = 0.01) and correlates with ethanol binge consumption (r2 = 0.68, p = 0.0008). ConclusionsThe present study demonstrates, for the first time, that trigeminal nerve injury, which induces CNOP, is enough to provide novelty seeking behaviour and lead to increasing ethanol intake. The increase of novelty seeking behaviour can serve as a predictor of risk of developing substance abuse. The treatment of CNOP involves a high risk of producing addiction. The level of novelty seeking evaluation in patients with neuropathic pain before treatment is critical.

Isolation stress and chronic mild stress induced immobility in the defensive burying behavior and a transient increased ethanol intake in Wistar rats.

Stress can be experienced with or without adverse effects, of which anxiety and depression are two of the most important due to the frequent comorbidity with alcohol abuse in humans. Historically, stress has been considered a cause of drug use, particularly alcohol abuse due to its anxiolytic effects. In the present work we exposed male Wistar rats to two different stress conditions: single housing (social isolation, SI), and chronic mild stress (CMS). We compared both stressed groups to group-housed rats and rats without CMS (GH) to allow the determination of a clear behavioral response profile related to their respective endocrine stress response and alcohol intake pattern. We found that SI and CMS, to a greater extent, induced short-lasting increased sucrose consumption, a transient increase in serum corticosterone level, high latency/immobility, and low burying behavior in the defensive burying behavior (DBB) test, and a transient increase in alcohol intake. Thus, the main conclusion was that stress caused by both SI and CMS induced immobility in the DBB test and, subsequently, induced a transient increased voluntary ethanol intake in Wistar rats with a free-choice home-cage drinking paradigm.

Further characterization of the GlyT-1 inhibitor Org25935: anti-alcohol, neurobehavioral, and gene expression effects

The glycine transporter-1 inhibitor Org25935 is a promising candidate in a treatment concept for alcohol use disorder targeting the glycine system. Org25935 inhibits ethanol-induced dopamine elevation in brain reward regions and reduces ethanol intake in Wistar rats. This study aimed to further characterise the compound and used ethanol consumption, behavioral measures, and gene expression as parameters to investigate the effects in Wistar rats and, as pharmacogenetic comparison, Alko-Alcohol (AA) rats. Animals were provided limited access to ethanol in a two-bottle free-choice paradigm with daily drug administration. Acute effects of Org25935 were estimated using locomotor activity and neurobehavioral status. Effects on gene expression in Wistar rats were measured with qPCR. The higher but not the lower dose of Org25935 reduced alcohol intake in Wistar rats. Unexpectedly, Org25935 reduced both ethanol and water intake and induced strong CNS-depressive effects in AA-rats (withdrawn from further studies). Neurobehavioral effects by Org25935 differed between the strains (AA-rats towards sedation). Org25935 did not affect gene expression at the mRNA level in the glycine system of Wistar rats. The data indicate a small therapeutic range for the anti-alcohol properties of Org25935, a finding that may guide further evaluations of the clinical utility of GlyT-1 inhibitors. The results point to the importance of pharmacogenetic considerations when developing drugs for alcohol-related medical concerns. Despite the lack of successful clinical outcomes, to date, the heterogeneity of drug action of Org25935 and similar agents and the unmet medical need justify further studies of glycinergic compounds in alcohol use disorder.

Benzyl alcohol increases voluntary ethanol drinking in rats

The anabolic steroid nandrolone decanoate has been reported to increase voluntary ethanol intake in Wistar rats. In recent experiments we received opposite results, with decreased voluntary ethanol intake in both high drinking AA and low drinking Wistar rats after nandrolone treatment. The difference between the two studies was that we used pure nandrolone decanoate in oil, whereas in the previous study the nandrolone product Deca-Durabolin containing benzyl alcohol (BA) was used. The aims of the present study were to clarify whether the BA treatment could promote ethanol drinking and to assess the role of the hypothalamic–pituitary–adrenal–gonadal axes (HPAGA) in the potential BA effect. Male AA and Wistar rats received subcutaneously BA or vehicle oil for 14days. Hereafter followed a 1-week washout and consecutively a 3-week voluntary alcohol consumption period. The median (±median absolute deviation) voluntary ethanol consumption during the drinking period was higher in BA-treated than in control rats (4.94±1.31g/kg/day vs. 4.17±0.31g/kg/day, p=0.07 and 1.01±0.26g/kg/day vs. 0.38±0.27g/kg/day, p=0.05, for AA and Wistar rats, respectively; combined effect p<0.01). The present results can explain the previous discrepancy between the two nandrolone studies. No significant BA effects on basal and ethanol-mediated serum testosterone and corticosterone levels were observed in blood samples taken at days 1, 8 and 22. However, 2h after ethanol administration significantly (p=0.02) higher frequency of testosterone elevations was detected in high drinking AA rats compared to low drinking Wistars, which supports our previous hypotheses of a role of testosterone elevation in promoting ethanol drinking. Skin irritation and dermatitis were shown exclusively in the BA-treated animals. Altogether, the present results indicate that earlier findings obtained with Deca-Durabolin containing BA need to be re-evaluated.

Differences in voluntary ethanol consumption in Wistar rats from five different suppliers

Understanding the mechanism of action of ethanol and the neurobiological substrates for alcohol use disorders is challenging. In search of this knowledge, it is imperative to use valid animal experimental models. The Wistar rat is one example of a commonly used strain that also exert foundation stock for several rat lines selectively bred for high and low voluntary ethanol intake. Different studies report varying ethanol intake in Wistar rats posing the question of whether this is because of the methodological differences or the rat strain. The purpose of this study was therefore to compare voluntary ethanol intake in Wistar rats from five different suppliers. Rats from B&K Universal, UK (BK); Charles River, Germany; Harlan Laboratories, IN (Hsd); Harlan Laboratories, The Netherlands (RccHan™); and Taconic, Denmark were exposed to a three-bottle free-choice paradigm with intermittent 24 h access to 5 and 20% ethanol and water three times per week for 6 weeks. A general finding was that the RccHan™ rats differed significantly from the other groups. At the end of the experiment, the RccHan™ group had the highest median ethanol intake of 3.85 g/kg/24 h, whereas the BK rats had the lowest intake of 1.84 g/kg/24 h. The preference for ethanol was also different throughout the experiment. At the end of the experiment, the RccHan™ rats had the highest preference of approximately 80%, whereas the BK rats had the lowest preference around 25%. During the 6-week drinking period, only the Hsd rats increased their ethanol intake, as evidenced by a significant increase of 5% ethanol intake. Although all rats are of Wistar origin, they display profound differences in voluntary ethanol consumption depending on the supplier. The choice of Wistar can therefore have implications for the outcome and make comparisons between studies difficult. The present findings highlight the supplier as an important parameter to consider when planning and performing preclinical animal studies in the field of alcohol research.

Short and Prolonged Periods of Maternal Separation and Voluntary Ethanol Intake in Male and Female Ethanol-Preferring AA and Ethanol-Avoiding ANA Rats

Genetic as well as environmental factors can affect the propensity for psychopathology and/or drug dependence. Maternal separation represents an animal experimental model that is useful in studies of effects of early life experiences. The authors have established a protocol for short and prolonged periods of maternal separation to study adult neurochemistry, behavior, and ethanol intake and have previously reported alterations in ethanol intake in Wistar rats and ethanol-preferring rats. The aim of the current study was to more thoroughly study how early life experiences affect an inherited propensity for high and low ethanol intake, respectively, in male and female ethanol-preferring AA (Alko alcohol) and ethanol-avoiding ANA (Alko, Non-Alcohol) rats. AA and ANA pups were assigned to one of three different rearing conditions: 15 min (MS15) or 360 min (MS360) of daily maternal separation in litters or normal animal facility rearing (AFR) during postnatal days 1 to 21. In adulthood, voluntary ethanol intake was investigated using the two-bottle free choice paradigm. In male ethanol-preferring AA rats, MS15 resulted in a lower intake and fewer high-preferring animals at 8% and 10% ethanol compared with MS360 rats. The male MS360 rats had a higher ethanol intake at 8% and 10% ethanol in comparison with AFR rats. In contrast, the female AA MS15 and MS360 rats had a lower ethanol intake and a lower preference for the 10% ethanol solution compared with the female AA AFR rats. In male and female ANA rats, no major separation-induced effects were found. The current results show that genetic inheritance can be affected by environmental manipulations in AA rats with an inherent high ethanol intake. The findings in female ethanol-preferring AA rats give further evidence of a differential outcome of maternal separation in male and female rats, as previously shown.

Effects of neuropeptide Y and corticotropin-releasing factor on ethanol intake in Wistar rats: interaction with chronic ethanol exposure

Neuropeptide Y (NPY) and corticotropin-releasing factor (CRF) have opposing effects on stress-associated and consummatory behaviors in rodents. Recent studies also suggest that both peptides influence ethanol intake. In the present study, the effects of administration of CRF and NPY into the lateral ventricle on ethanol intake in naive and ethanol-vapor-exposed Wistar rats were examined. A limited access paradigm was used to measure intake of a 10% (v/v) ethanol solution in Wistar rats trained to drink using a sucrose fading procedure. Ethanol vapor exposure for 8 weeks significantly elevated ethanol intake in this limited access paradigm relative to pre-exposure levels. The effects of icv administration of CRF (1 μg), NPY (10 μg) or NPY/CRF combined (10 and 1 μg, respectively) on ethanol intake were then assessed. In non-vapor-exposed subjects, icv infusion of NPY had no effect on ethanol intake, while a significant suppression of drinking was seen following icv administration of CRF. Administration of NPY in combination with CRF had no effect on ethanol intake in non-ethanol-vapor-exposed rats. In vapor-exposed subjects, both NPY and CRF reduced ethanol intake, but when given in combination, no difference from vehicle was detected. Locomotor activity was measured during drinking sessions and was unaffected by peptide administration. These studies underscore the importance of a history of exposure to chronic ethanol vapor in the regulation of ethanol intake by NPY. Furthermore, the results presented here suggest that a balance between the stress-related peptides NPY and CRF may be involved in the regulation of ethanol intake.

Effect of Neuropeptide Y (NPY) on Oral Ethanol Intake in Wistar, Alcohol-Preferring (P), and -Nonpreferring (NP) Rats

Background: Neuropeptide Y (NPY) deficient mice consume more ethanol than controls, whereas NPY over-expressing mice consume less ethanol than controls. Thus, ethanol drinking may be inversely associated with NPY activity. To determine whether exogenously administered NPY would alter ethanol intake, two experiments were conducted. Methods: A within-subject design was used with intracerebroventricular (ICV) administration of NPY or artificial cerebral spinal fluid (aCSF) into the lateral ventricles. Infusions were separated by 2 to 7 days. In experiment 1, male Wistar rats (n= 10) were tested for the effects of NPY on an intake of 5% sucrose or 8% (w/v) ethanol during daily 2-hr testing periods with food and water available at all other times. In experiment 2, male alcohol-preferring (P) and alcohol-nonpreferring (NP) rats (n= 8/line) were tested for the effects of NPY on 8% (w/v) ethanol intake. Results: In experiment 1, NPY (5, 10, 20 μg) significantly increased sucrose intake relative to aCSF baseline in Wistar rats, a finding consistent with previous observations of the orexigenic effects of the peptide. However, NPY (10 μg) did not alter ethanol intake in Wistar rats. In experiment 2, NPY (5 and 10 μg) significantly decreased ethanol intake in P rats, but not in NP rats. Conclusion: The reduction in ethanol intake seen with the P rats is consistent with the postulated negative relationship between NPY activity and ethanol intake. The lack of effect of NPY on ethanol intake in Wistar and NP rats may be related to the lower baseline levels of ethanol intake in these rats or to differential central nervous system basal NPY activity or sensitivity to the peptide.

Effect of Neuropeptide Y (NPY) on Oral Ethanol Intake in Wistar, Alcohol‐Preferring (P), and ‐Nonpreferring (NP) Rats

Neuropeptide Y (NPY) deficient mice consume more ethanol than controls, whereas NPY over-expressing mice consume less ethanol than controls. Thus, ethanol drinking may be inversely associated with NPY activity. To determine whether exogenously administered NPY would alter ethanol intake, two experiments were conducted. A within-subject design was used with intracerebroventricular (ICV) administration of NPY or artificial cerebral spinal fluid (aCSF) into the lateral ventricles. Infusions were separated by 2 to 7 days. In experiment 1, male Wistar rats (n = 10) were tested for the effects of NPY on an intake of 5% sucrose or 8% (w/v) ethanol during daily 2-hr testing periods with food and water available at all other times. In experiment 2, male alcohol-preferring (P) and alcohol-nonpreferring (NP) rats (n = 8/line) were tested for the effects of NPY on 8% (w/v) ethanol intake. In experiment 1, NPY (5, 10, 20 microg) significantly increased sucrose intake relative to aCSF baseline in Wistar rats, a finding consistent with previous observations of the orexigenic effects of the peptide. However, NPY (10 microg) did not alter ethanol intake in Wistar rats. In experiment 2, NPY (5 and 10 microg) significantly decreased ethanol intake in P rats, but not in NP rats. The reduction in ethanol intake seen with the P rats is consistent with the postulated negative relationship between NPY activity and ethanol intake. The lack of effect of NPY on ethanol intake in Wistar and NP rats may be related to the lower baseline levels of ethanol intake in these rats or to differential central nervous system basal NPY activity or sensitivity to the peptide.

Evidence that the amygdala is involved in the inhibitory effects of 5-HT 3 receptor antagonists on alcohol drinking in rats

Two 5-HT 3 receptor antagonists, tropisetron (1 and 10 ng) and ondansetron (10 and 100 ng) were tested for effects on ethanol drinking in Wistar male rats after bilateral microinjection into the amygdala. The animals had limited access (2 h/day) to the 10% (v/v) ethanol solution, food and water were available ad lib during the scheduled access period. Both drugs caused a decrease in ethanol drinking. Tropisetron (1 and 10 ng) decreased ethanol intake during the first hour of access. The lower dose (10 ng) of ondansetron was more effective than the higher (100 ng) dose. The finding implicates amygdaloid 5-HT 3 receptors in the mechanism of ethanol intake in Wistar rats.

Median and dorsal raphe injections of the 5-HT 1A agonist, 8-OH-DPAT, and the GABA A agonist, muscimol, increase voluntary ethanol intake in wistar rats

Low doses of the selective 5-HT 1A agonist 8-OH-DPAT increase ethanol intake in a limited access paradigm following peripheral injection. This may be due to a reduction in 5-HT neurotransmission following activation of raphe somatodendritic autoreceptors. In order to test this hypothesis, and to determine the effects of selective reductions in raphe 5-HT activity, experiments examined the effects of injecting 8-OH-DPAT into the dorsal raphe (0, 0.02, 0.1, 1 and 2.5 μg) or the median raphe (0, 0.1, 1 and 5 μg) in rats trained to drink 12% ethanol for 40 min each day. The effects of the GABA A agonist, muscimol, on ethanol intake were also examined. Ethanol intake was increased at the highest dose of 8-OH-DPAT following injection into either site, with no change in water intake. Thus, the effects of 8-OH-DPAT are selective for ethanol. The selective 5-HT 1A antagonist, (+)-WAY100135 (0.3, 1 and 3 mg/kg), blocked the effect of 8-OH-DPAT, showing that activation of 5-HT 1A receptors underlies the ethanol drinking induced by 8-OH-DPAT. These results are consistent with the idea that reduced 5-HT function increases ethanol intake. Several behavioural mechanisms for this effect are discussed. Muscimol (50–100 ng) also increased ethanol drinking. Following injection into the median raphe, muscimol also stimulated water intake. These effects are probably due to non-specific behaviourl activation induced by this treatment. However, the effect of muscimol in the dorsal raphe was specific for ethanol since water intake was not altered. Together, these results imply that serotonergic elements within the dorsal and median raphe, as well as non-serotonergic elements within the dorsal raphe may represent important neurochemical systems controlling ethanol drinking.