The effects of cyclic 3'5' adenosine monophosphate on the acute tolerance induced by ethanol in male rats.

The effect of cyclic 3′5′ adenosine monophosphate (cAMP) on the acute tolerance induced by ethanol was studied in male rats. The acute tolerance was measured with a hexobarbital anesthesia method, where the dose of hexobarbital needed to obtain a burst suppression of 1 second or more in EEG is determined. Ethanol 2.0 g/kg was given ip 0.25 or 3 h prior to the threshold determination. cAMP 10 mg/kg or saline was given iv 6 h prior to the threshold determination.After saline pre-treatment less hexobarbital was needed 0.25 h after ethanol administration compared to 3 h after ethanol administration, although the blood levels were similar. An acute tolerance had developed. Pre-treatment with cAMP had no effect on the dose of hexobarbital needed without ethanol nor on the dose needed 3.0 h after ethanol administration. 0.25 h after ethanol more hexobarbital was needed in the animals pre-treated with cAMP compared with the corresponding saline treated animals. The dose of hexobarbital was as large as the one needed 3.0 h after ethanol. Thus cAMP seems to facilitate the induction of acute tolerance to ethanol while the hexobarbital threshold as such is uninfluenced.     

Influence of small doses of various drug vehicles on acetaminophen-induced liver injury

The biological effects of drug vehicles are often overlooked, often leading to artifacts in acetaminophen-induced liver injury assessment. Therefore, we decided to investigate the effect of dimethylsulfoxide, dimethylformamide, propylene glycol, ethanol, and Tween 20 on acetaminophen-induced liver injury. C57BL/6 male mice received a particular drug vehicle (0.6 or 0.2 mL/kg, i.p.) 30 min before acetaminophen administration (300 mg/kg, i.p.). Control mice received vehicle alone. Liver injury was assessed by measuring the concentration of alanine aminotransferase in plasma and observing histopathological changes. The level of reduced glutathione (GSH) was assessed by measuring total nonprotein hepatic sulfhydrils. Dimethylsulfoxide and dimethylformamide (at both doses) almost completely abolished acetaminophen toxicity. The higher dose of propylene glycol (0.6 mL/kg) was markedly protective, but the lower dose (0.2 mL/kg) was only slightly protective. These solvents also reduced acetaminophen-induced GSH depletion. Dimethylformamide was protective when given 2 h before or 1 h after acetaminophen administration, but was ineffective if given 2.5 h after acetaminophen. Ethanol at the higher dose (0.6 mL/kg) was partially protective, whereas ethanol at the lower dose (0.2 mL/kg) as well as Tween 20 at any dose had no influence. None of the vehicles (0.6 mL/kg) was hepatotoxic per se, and none of them was protective in a model of liver injury caused by D-galactosamine and lipopolysaccharide.     

Development of tolerance to ethanol-induced suppression of breathing movements and brain activity in the near-term fetal sheep during short-term maternal administration of ethanol

The effect of short-term maternal ethanol administration on the ethanol-induced suppression of fetal breathing movements, electrocortical (ECoG) activity, and electroocular (EOG) activity was determined in the near-term fetal sheep. Twelve conscious instrumented pregnant ewes (between 125 and 139 days of gestation; term, 147 days) received 1-h intravenous infusion of 1 g ethanol/kg total body weight daily for six days (n = 6) or an equivalent volume of normal saline daily for six days (n = 6). On the seventh day, the ethanol- and saline-pretreated animals were administered 1 g ethanol/kg total body weight. A further six ewes received 1-h intravenous infusion of 1 g ethanol/kg total body weight (n = 3) or an equivalent volume of normal saline (n = 3) daily for thirteen days with both groups receiving 1 g ethanol/kg total body weight on day fourteen. Fetal ECoG and EOG activities, and fetal breathing movements were monitored continuously over the post- operative and experimental periods. Saline infusion had no significant effect on the parameters studied. Fetal breathing movements were suppressed for 8 h after the first ethanol dose, and were not significantly suppressed after fourteen days of once-daily, maternal ethanol administration. Low-voltage ECoG and EOG activities were suppressed for 3 h after the first ethanol dose, and were not significantly suppressed after seven days of repeated ethanol administration. Maternal and fetal blood gases and acid-base balance were not significantly affected by maternal ethanol administration. These data demonstrate that short-term maternal administration of ethanol results in the development of tolerance to ethanol in the mature fetus.     

Dominance and aggression in social groups of male and female rats

Two experiments were performed to examine aggression and dominance in domestic male and female $\text{Rattus norvegicus}$ living in small mixed-sex (3 males and 3 females) groups. Experiment 1 examined the development of aggression in females. A single female (alpha) within each of the six colonies tested showed the preponderance of attacks on male intruders placed into the home-cage when male colony residents were absent. Over 12 weeks of intruder-aggression training female alphas showed only a mild nonsignificant elevation of aggressive behavior. A comparison of aggression of male and female colony alphas tested with opponents of each sex revealed that aggression was mainly directed at like-sex opponents, and that female attack was more defensive in character than male attack regardless of opponent sex. The highest intensity of aggression occurred when male alphas confronted male intruders. Although intruders never showed offense toward male residents, 61% of intruding males showed offense in response to attack by females.Experiment 2 investigated the relationship between aggressive dominance and competitive measures of dominance within each of 10 mixed-sex colonies. Alpha stat s of male and female colony residents did not reliably predict priority of access to food or water in tests of direct resource competition with like-sex colony members. When colony males were simultaneously tested for copulation, the copulatory behavior of alpha males was significantly greater than that of other colony males. Results are discussed in relation to the role of aggression in the reproductive strategy of male and female $\text{Rattus norvegicus}$.     

Studies on effects of tamoxifen (ICI 46474) on agonistic encounters between pairs of intact mice

The anti-estrogen tamoxifen (Tam), which has been shown to dramatically suppress offensive behavior in male rats without markedly influencing other aspects of the social encounter, was tested for its effectiveness in mice. TO strain albino mice were given control injections or 50 or 100 micrograms of Tam for 4 or 8 days. Subsequently, mice were tested in pairs (for a particular dose and treatment duration) in which both animals received Tam, one animal received Tam and one saline, or both animals received saline control injections. Ten-minute videotaped encounters were analyzed in terms of total times allocated to nonsocial investigation, social investigation, offense, defense, sexual activity/intense social investigation, and immobility. The lower dose given for the shorter duration produced less social investigation and more nonsocial investigation when Tam-treated subjects were paired together (cf. the Tam vs saline pairing). At all the other doses and durations, Tam reduced offense. Defense also changed in those pairings, but that activity seemed related to the amount of attack received. Tamoxifen had little influence on the weights of accessory sex glands. The data confirm that Tam is a potent suppressor of "androgen-dependent" aggression in male laboratory mice and provide further support for the aromatization hypothesis.     

Modulation of diaspirin crosslinked hemoglobin induced systemic and regional hemodynamic response by ethanol in normal rats

DCLHb, a hemoglobin based oxygen carrier, has been extensively studied for the treatment of hemorrhagic shock in both animal models and humans. Numerous accidents resulting in trauma are due to ethanol intoxication, in particular cases of car accidents. Therefore, trauma patients might be intoxicated with drugs of abuse like ethanol. Ethanol has significant effects on the cardiovascular system including peripheral vasodilation and decreased myocardial contractility. Such effects are likely to alter the cardiovascular actions of DCLHb, a resuscitative agent. Hence, this study investigated the effect of ethanol on the cardiovascular actions of DCLHb. Urethane anesthetized male Sprague-Dawley rats were divided into following groups (i) Saline + DCLHb (400 mg/kg) (n = 9), (ii) Ethanol (1 g/kg) + DCLHb (400 mg/kg) (n = 9), and (iii) Ethanol (4 g/kg) + DCLHb (400 mg/kg) (n = 8). Cardiovascular parameters were determined using a radioactive microsphere technique. DCLHb when administered to saline treated rats produced an increase in MAP, TPR, decreased renal and hepatic blood flow and increased blood flow to the skin and mesentery & pancreas. A high dose of ethanol (4 g/kg) significantly attenuated the DCLHb induced pressor response (p < 0.05) and increase in TPR (p < 0.05). Cardiac output was severely reduced by DCLHb in rats treated with high dose ethanol as compared to saline. No changes in TPR and cardiac output were observed in the low dose ethanol (1 g/kg) group. DCLHb reduced blood flow to the heart and mesentery & pancreas in rats treated with high dose ethanol. DCLHb caused a decrease in musculo-skeletal vascular resistance in rats treated with high dose ethanol. This decrease in vascular resistance in the musculo-skeletal system appears to be contributing to a decrease in TPR. It is concluded that ethanol in higher doses significantly alters the hemodynamic effects of DCLHb and may interfere with the resuscitative effects of DCLHb.     

Effects of ethanol on locomotor and anxiety-like behaviors and the acquisition of ethanol intake in Lewis and spontaneously hypertensive rats

The purpose of the present study was to investigate whether Lewis (LEW) and spontaneously hypertensive rats (SHR), characterized in numerous behavioral tests as strains with high-anxiety and low-anxiety, respectively, could differ in their sensitivity to the effects of ethanol in the elevated plus maze (EPM) and the open field (OF), two classical models of anxiety/emotionality, as well as in the acquisition of ethanol drinking behavior. It was also of interest to examine the relationship between sweet and bitter fluids preference and ethanol intake. SHR and LEW rats were given saline or ethanol injections (0.6 or 1.2 g/kg, ip.) and tested in the EPM and OF. Subsequently the same animals were given continuous free choice between water and ethanol solution (2-8%). Additional groups of animals were exposed to a free-choice regimen between saccharin (0.002-0.09%) or quinine (0.0001-0.0015%) and water. The low dose of ethanol (0.6 g/kg) induced anxiolytic-like effects and intensive locomotor activation mainly in SHR rats tested in the OF arena. Overall, LEW counterparts were unaffected in OF test. In oral self-administration paradigm, SHR rats consumed significantly more ethanol than LEW rats. Concerning other solutions, SHR rats consumed large amounts of saccharin compared with LEW rats. These data indicate that the SHR preference for ethanol intake may be positively related to their differential sensitivity to the anxiolytic/stimulant effects of ethanol and to the sensitivity of this strain for saccharin reinforcement. In addition, these findings provide evidence that the SHR strain may represent a useful genetic and pharmacological tool to investigate ethanol drinking traits.     

Ghrelin's quick inhibition of androgen-dependent behaviors of male house mice (Mus musculus)

Ghrelin is a peptide hormone released by the stomach that stimulates hunger. Ghrelin also suppresses reproductive physiology by inhibiting the HPG axis. However, to our knowledge, our results are the first to demonstrate ghrelin's quick suppression of sex-hormone-regulated behaviors. In experiment 1, 2 orexigenic i.p. ghrelin injections (0.165 mg/kg and 0.33 mg/kg) suppressed male courtship behavior (ultrasonic calling to a female) and intermale aggression (latency to attack a stimulus male) 20 min following administration. Experiment 2 (examining only the 0.33 mg/kg dose ) replicated ghrelin's suppression of ultrasonic calling and intermale aggression; however, a third behavior, preference for volatile female odors (20 min following administration), was not significantly inhibited. In experiment 2, ghrelin treatment did not affect general locomotor activity (distance traveled 20 min following injection) or seminal vesicle weight (measured 5 days after completing ghrelin injections). We hypothesize that ghrelin's quick suppression of male aggression and ultrasonic mating calls was mediated through its effects on the brain (rather than indirectly through inhibition of the HPG axis).     

Pregnancy outcomes after weekly oral administration of ethanol during gestation in the pig-tailed macaque (Macaca nemestrina)

Ethanol was orally administered once per week to gravid pig-tailed macaques (Macaca nemestrina) in doses of 0.3, 0.6, 1.2, 1.8, 2.5, 3.3, or 4.1 g/kg. A control group received a sucrose solution, isocaloric and isovolemic to the highest ethanol dose. Pregnancy was followed after 116 possible conceptions in 54 females. Peak plasma ethanol concentrations (PPECs) ranged from 24 +/- 6 mg/dl at the 0.3 g/kg dose to 549 +/- 71 mg/dl at the 4.1 g/kg dose. An increased rate of spontaneous abortion was related to ethanol exposure at and above 1.8 g/kg (mean PPEC = 205 mg/dl). Pregnancy failure in the first 30 days of gestation increased at doses above 2.5 g/kg. The effect on pregnancy outcome of weekly exposure to ethanol in this nonhuman primate is comparable to available data on humans. The methodology of this study represents an effective model for studying ethanol teratogenesis in a nonhuman primate.     

Changes in Histamine Metabolism in the Mouse Hypothalamus Induced by Acute Administration of Ethanol

The effect of acute ethanol administration on histamine (HA) dynamics was examined in the mouse hypothalamus. The steady-state level of HA did not change after intraperitoneal administration of ethanol (0.5-5 g/kg), whereas the level of tele-methylhistamine (t-MH), a predominant metabolite of brain HA, increased when 3 and 5 g/kg of ethanol was given. Pargyline hydrochloride (80 mg/kg, i.p.) increased the level of t-MH by 72.2% 90 min after the treatment. Ethanol at any dose given did not significantly affect the t-MH level in the pargyline-pretreated mice. Decrease in the t-MH level induced by metoprine (10 mg/kg, i.p.), an inhibitor of HA-N-methyltransferase, was suppressed by ethanol (5 g/kg), thereby suggesting inhibition of the elimination of brain t-MH. Ethanol (5 g/kg) significantly delayed the depletion of HA induced by (S)-alpha-fluoromethylhistidine (50 mg/kg, i.v.), a specific inhibitor of histidine decarboxylase. Therefore, a large dose of ethanol apparently decreases HA turnover in the mouse hypothalamus.     

Comparison between multiple behavioral effects of peripheral ethanol administration in rats: sedation, ataxia, and bradykinesia

Although low doses of systemic ethanol stimulate locomotion in mice, in rats the typical response to peripheral ethanol administration is a dose-dependent suppression of motor activity. In the present study, male rats received acute doses of ethanol IP (0.0, 0.25, 0.5, 1.0 or 2.0 g/kg) and were tested on several behavioral tasks related to the motor suppressive or sedative effects of the drug. This research design allowed for comparisons between the effects of ethanol on different behavioral tasks in order to determine which tasks were most sensitive to the drug (i.e., which tasks would yield deficits that appear at lower doses). In the first two experiments, rats were evaluated on a sedation rating scale, and ataxia/motor incoordination was assessed using the rotarod apparatus. Administration of 2.0 g/kg ethanol produced sedation as measured by the sedation scale, and also impaired performance on the rotarod. In a third experiment, ethanol reduced locomotion in the stabilimeter at several doses and times after IP injection, with 0.25 g/kg being the lowest dose that produced a significant decrease in locomotion. Finally, experiment four studied the effects of ethanol on operant lever pressing reinforced on a fixed ratio 5 (FR5) schedule for food reinforcement. Data showed suppressive effects on lever pressing at doses of 1.0, and 2.0 g/kg ethanol. Analysis of the interresponse time distribution showed that ethanol produced a modest slowing of operant responding, as well as fragmentation of the temporal pattern of responding and increases in pausing. Taken together, these results indicate that rats can demonstrate reduced locomotion and slowing of operant responding at doses lower than those that result in sedation or ataxia as measured by the rotarod. The detection of subtle changes in different motor test across a broad range of ethanol doses is important for understanding ethanol effects in other cognitive, motivational or sensory processes.     

Systemic injections of gastro-intestinal peptides alter behavior in rats

Twenty-four male albino rats were given daily intraperitoneal injections of vasoactive intestinal polypeptide (VIP), motilin, human gastrin I (1–17) or the diluent control vehicle at a dose of 100 μg/kg for four consecutive days and food intake, water intake, body weight, and running wheel activity were determined every 24 hours. Animals injected with motilin or human gastrin I (1–17) exhibited decreased food intake relative to those injected with VIP or diluent, which did not differ from each other, although food intake increased reliably over days. The mean water consumption followed the same pattern as that of food intake. As expected from the above results, VIP produced weight gains as compared with rats injected with motilin or gastrin but not reliably more than after diluent. A reliable effect of trials for weight gain was the greatest on day three. Running wheel activity was not affected by injections of human gastrin I (1–17), motilin, or diluent but was reliably decreased by VIP. No significant differences existed across days. Although the results indicate that GI peptides may affect behavior when injected systemically and that like other peptides they have multiple effects, caution is urged in the interpretation of behavioral results at this time.     

In vivo studies of ethanol on prolactin and luteinizing hormone in rats and mice

The interaction of ethanol (EtOH), prolactin (Prl) and luteinizing hormone (LH) was examined in two studies. In the first study, adult male C57 B1/6J mice were given a single intraperitoneal injection of either vehicle or Prl at 5, 10 and 20 mg/kg and a significant dose-related suppression of ethanol consumption was found. This injection did not cause any differences in food intake or body weight. Additionally, a 5 mg/kg dose of Prl was also given to adult male Long Evans Hooded rats and, similarly, there was a significant suppression of ethanol consumption. In a second study, when rats were given a free choice between water and 5% EtOH, three subgroups were found regarding the amount of EtOH consumption: low, medium and high. After 2 weeks of free choice, hypothalamic, but not serum Prl and LH levels, were significantly increased in EtOH-imbibing groups compared to controls. These findings suggest important interactions between EtOH consumption and ambient levels of Prl and LH.     

Modulation of elevated plus maze behavior after chronic exposure to the anabolic steroid 17alpha-methyltestosterone in adult mice

Exposure to supraphysiological doses of androgens may disrupt affective components of behavior. In this study, behavior of adult C57Bl/6 male mice was studied after exposure to the anabolic androgenic steroid (AAS) 17alpha-methyltestosterone (17alpha-meT; 7.5 mg/kg) via a subcutaneous osmotic pump for 17 days. Controls received vehicle implants (0.9% NaCl + 30% cyclodextrine). On day 15, experimental animals were challenged with an ethanol (EtOH) injection (i.p.; 1 g/kg) while controls received saline injections. Five minutes after the injection, animals were tested in an automated elevated plus maze (EPM) or in automated activity chambers. In addition, injection-free animals were tested for ethanol consumption on day 16 after an overnight water deprivation period. Whereas chronic exposure to 17alpha-meT did not modulate open arm behavior, EtOH-exposed animals made more entries into the open arms than controls (P < 0.05). A significant reduction of risk assessment behaviors (rearing, flat approach behavior, and stretch attended posture) over the EPM was noted for EtOH-exposed animals whereas a reduction in stretch attended postures was observed among 17alpha-meT-exposed animals. Locomotor activity, and light-dark transitions in activity chambers remained unaltered. Exposure to AAS did not modulate EtOH consumption. Our data suggest that exposure to a supraphysiological dose of 17alpha-meT has minimal effects on exploratory-based anxiety.     

Binge Ethanol Prior to Traumatic Brain Injury Worsens Sensorimotor Functional Recovery in Rats

A significant number of patients suffering from traumatic brain injury (TBI) have a high blood alcohol level at the time of injury. Furthermore, drinking alcohol in a binge-like pattern is now recognized as a national problem, leading to a greater likelihood of being injured. Our objective was to determine the consequences of a binge paradigm of alcohol intoxication at the time of TBI on long-term functional outcome using a sensitive test of sensorimotor function. We trained adult, male, Sprague Dawley rats on the skilled forelimb reaching task and then administered a single binge dose of ethanol (2g/kg, i.p.) or saline for three consecutive days (for a total of 3 doses). One hour after the final ethanol dose, rats underwent a TBI to the sensorimotor cortex corresponding to the preferred reaching forelimb. Animals were then tested for seven weeks on the skilled forelimb reaching task to assess the profile of recovery. We found that the group given ethanol prior to TBI displayed a slower recovery curve with a lower recovery plateau as compared to the control group. Therefore, even a relatively short (3 day) episode of binge alcohol exposure can negatively impact long-term recovery from a TBI, underscoring this significant public health problem.     

Contractile function, glucose consumption and lactate release by the isolated rat heart during different regimens of alcohol administration and after discontinuation of ethanol

Acute or chronic intoxication of rats with ethanol (intragastric administration at a dose of 8 g/kg or free-choice drinking of 10% ethanol for 3 months) produced no significant changes in contractile function, glycogen content, glucose uptake and lactate release in isolated hearts. Withdrawal syndrome simulated in rats following a short period of severe intoxication with ethanol at a dose of 4-5 g/kg twice daily has demonstrated a 15 and 28% decrease in peak systolic pressure and tension time index, respectively. In this case glucose uptake and lactate release were 2 times higher. Changes in glycogen level were observed three days after the last ethanol administration. The rats, survived after the abstinence period, revealed areas of perivascular myocardial necrosis. It is concluded that withdrawal syndrome plays an important role in pathogenesis of alcoholic cardiomyopathy.     

Systemic injections of gastro-intestinal peptides alter behavior in rats

Twenty-four male albino rats were given daily intraperitoneal injections of vasoactive intestinal polypeptide (VIP), motilin, human gastrin I (1–17) or the diluent control vehicle at a dose of 100 μg/kg for four consecutive days and food intake, water intake, body weight, and running wheel activity were determined every 24 hours. Animals injected with motilin or human gastrin I (1–17) exhibited decreased food intake relative to those injected with VIP or diluent, which did not differ from each other, although food intake increased reliably over days. The mean water consumption followed the same pattern as that of food intake. As expected from the above results, VIP produced weight gains as compared with rats injected with motilin or gastrin but not reliably more than after diluent. A reliable effect of trials for weight gain was the greatest on day three. Running wheel activity was not affected by injections of human gastrin I (1–17), motilin, or diluent but was reliably decreased by VIP. No significant differences existed across days. Although the results indicate that GI peptides may affect behavior when injected systemically and that like other peptides they have multiple effects, caution is urged in the interpretation of behavioral results at this time.     

Different patterns in the induction of metallothionein mRNA synthesis among isoforms after acute ethanol administration

The induction of metallothionein (MT) isoform synthesis was investigated in mouse cerebral cortex 18 h after oral ethanol administration. The expression of MT-I isoform mRNA increased in a dose-dependent manner after ethanol loading at doses between 2 g/kg (ethanol/body weight) and 8 g/kg. Lipid peroxide formation, measured as the amount of malondialdehyde-reactive substances, remained at the control level after all of the administered ethanol doses. The expression of MT-III isoform mRNA remained at the control level up until an ethanol loading dose of 4 g/kg and then finally increased to a significant level at a dose of 8 g/kg, which is almost the LD₅₀ for oral ethanol in mice. The different patterns of MT synthesis induction among MT isoforms suggests that the MT-I isoform, which is ubiquitous in mammalian tissues, plays a significant role as an antioxidant. On the other hand, the MT-III isoform, which has a limited tissue distribution, especially in the central nervous system, seems to be implicated in tissue repair and/or protection against critical tissue injury.     

Co-Segregation of Intermale Aggression with the Pseudoautosomal Region of the Y Chromosome in Mice

The sexual dimorphism of aggression has led to a search for its Y chromosomal correlates. We have previously confirmed that initiation of attack behavior against a conspecific male is Y-dependent in two strains of laboratory mice (NZB and CBA/H). We provide evidence that the non-pseudoautosomal region of the Y is not involved and that only the pseudoautosomal region of the Y is correlated with initiation of attack behavior. The autosomal correlates also contribute to this behavior in an additive or interactive manner with the pseudoautosomal correlates.     

The benzodiazepine receptor inverse agonists FG 7142 and RO 15-4513 both reverse some of the behavioral effects of ethanol in a holeboard test

The intrinsic effect of the benzodiazepine receptor inverse agonists RO 15-4513 and FG 7142 on the behavior of mice in a holeboard were investigated. Both drugs caused dose-related decreases in exploratory head-dipping. The highest dose of FG 7142 (40 mg/kg) also reduced locomotor activity. RO 15-4513 (1.5 and 3.0 mg/kg) and FG 7142 (10 and 20 mg/kg) reversed the reductions in the number of head-dips caused by ethanol (2 g/kg). The higher doses of these two drugs also partially reversed the locomotor stimulant action of ethanol. Animals that received ethanol in combination with either inverse agonist spent less time head-dipping than vehicle-treated controls. These data indicate that FG 7142 and RO 15-4513 can reverse, at least in part, some of the behavioral effects of ethanol. Neither drug significantly altered blood alcohol concentrations suggesting that the antagonism does not result from pharmacokinetic changes.