Unpredictable cold-immobilization stress effects on voluntary ethanol consumption in rats

The effects of exposure to a schedule of unpredictable cold-immobilization stress on voluntary ethanol consumption were examined. Following testing for ethanol preference, rats were divided into high, medium and low ethanol consuming groups on the basis of daily ethanol intake (g/kg/day) and exposed to immobilization stress over an 18 day period. Voluntary ethanol consumption was monitored during the stress period and for an additional 36 days post-stress. Results indicated a differential effect of stress on ethanol intake in that low ethanol consuming rats increased their ethanol intake during the stress period and maintained this increase throughout the entire post-stress period as compared to non-stressed controls. High ethanol consuming groups demonstrated a small (marginally significant) decrease in ethanol intake during the stress period as compared to baseline levels. No change in ethanol intake was observed for the medium ethanol consuming groups. The results suggest that unpredictable immobilization stress has a differential effect on ethanol intake depending upon pre-stress levels of ethanol consumption.     

Moderate alcohol consumption: effects on lipids and cardiovascular disease risk

Light to moderate alcohol consumption is associated with a reduced risk of coronary heart disease, as well as ischaemic stroke and possibly type 2 diabetes. Epidemiological and physiological data are in favour of a causal relationship. Proposed protective mechanisms include the stimulation of HDL-mediated processes such as reverse cholesterol transport and antioxidative effects. More well-controlled studies are needed to provide a complete understanding of the complexity of the underlying physiological mechanisms.     

Effects of stress and alcohol consumption on emotional/motivational behavior of rats and their first generation offspring

Neurophysiological manifestations of formation of the dependence on ethanol under stress conditions were studied in rats and their first generation offspring. In chronic experiments on 32 male rats, emotional stress was modeled (induction by nociceptive electrocutaneous stimulation), and an increased addiction to ethanol was formed. In these animals and in the first generation of their offspring (obtained from the above males and intact females), we studied emotional/motivational behavior, recorded the mass electrical activity from different brain structures, and measured the arterial pressure. In stressed rats, which acquired attraction to ethanol, negative emotional responses became transformed into positive, and behavioral and electrographic manifestations of the seizure activity developed. In the first generation offspring, the pattern of central rearrangements in the mechanisms of emotional/motivational behavior was to a great extent similar to that in parent rats.     

Fetal testosterone surge: specific modulations induced in male rats by maternal stress and/or alcohol consumption

Plasma testosterone (T) was measured in control male and female rats on gestational days 16, 17, 18, 19, and 20 and on days 17-20 in males from dams who were fed ethanol and/or were stressed during pregnancy. Circulating T in control males showed an earlier rise, yielding a longer period of prenatal T elevation, than was reported previously (Endocrinology 106 (1980)306). Compared to control males, exposure to alcohol-alone augmented T on days 18 and 19, stress-alone attenuated prenatal T, and the combination of stress and alcohol completely blocked the normal rise in T between days 17 and 18. When these prenatal alterations in T are viewed along with effects these same treatments have on the postparturient T surge (Horm. Behav. 41 (2002) 229), a possible explanatory mechanism emerges for the uniquely different behavioral patterns of sexual behavior differentiation induced in males by prenatal exposure to alcohol, stress, or both factors. Whereas the potential for feminine behavior is retained to the extent that either the prenatal or the neonatal T surge is attenuated, the male potential is more sensitive to reductions in the fetal surge and is maximally disrupted if both the prenatal and the postparturitional T surges are suppressed.     

Genetical genomic determinants of alcohol consumption in rats and humans

Background

We have used a genetical genomic approach, in conjunction with phenotypic analysis of alcohol consumption, to identify candidate genes that predispose to varying levels of alcohol intake by HXB/BXH recombinant inbred rat strains. In addition, in two populations of humans, we assessed genetic polymorphisms associated with alcohol consumption using a custom genotyping array for 1,350 single nucleotide polymorphisms (SNPs). Our goal was to ascertain whether our approach, which relies on statistical and informatics techniques, and non-human animal models of alcohol drinking behavior, could inform interpretation of genetic association studies with human populations.

Results

In the HXB/BXH recombinant inbred (RI) rats, correlation analysis of brain gene expression levels with alcohol consumption in a two-bottle choice paradigm, and filtering based on behavioral and gene expression quantitative trait locus (QTL) analyses, generated a list of candidate genes. A literature-based, functional analysis of the interactions of the products of these candidate genes defined pathways linked to presynaptic GABA release, activation of dopamine neurons, and postsynaptic GABA receptor trafficking, in brain regions including the hypothalamus, ventral tegmentum and amygdala. The analysis also implicated energy metabolism and caloric intake control as potential influences on alcohol consumption by the recombinant inbred rats. In the human populations, polymorphisms in genes associated with GABA synthesis and GABA receptors, as well as genes related to dopaminergic transmission, were associated with alcohol consumption.

Conclusion

Our results emphasize the importance of the signaling pathways identified using the non-human animal models, rather than single gene products, in identifying factors responsible for complex traits such as alcohol consumption. The results suggest cross-species similarities in pathways that influence predisposition to consume alcohol by rats and humans. The importance of a well-defined phenotype is also illustrated. Our results also suggest that different genetic factors predispose alcohol dependence versus the phenotype of alcohol consumption.     

Shear stress and shear rate differentially affect the multi-step process of leukocyte-facilitated melanoma adhesion

Previous studies have shown that neutrophils (PMNs) facilitate melanoma cell extravasation [M.J. Slattery, C. Dong, Neutrophils influence melanoma adhesion and migration under flow conditions, Intl. J. Cancer 106 (2003) 713–722] Little is known, however, about the specific interactions between PMNs, melanoma and the endothelium (EC) or the molecular mechanism involved under flow conditions. The aim of this study is to investigate a “two-step adhesion” hypothesis that involves initial PMN tethering on the EC and subsequent melanoma cells being captured by tethered PMNs. Different effects of hydrodynamic shear stress and shear rate were analyzed using a parallel-plate flow chamber. Results indicate a novel finding that PMN-facilitated melanoma cell arrest on the EC is modulated by shear rate, which is inversely-proportional to cell–cell contact time, rather than by the shear stress, which is proportional to the force exerted on formed bonds. β₂ integrins/ICAM-1 adhesion mechanisms were examined and the results indicate LFA-1 and Mac-1 cooperate to mediate the PMN–EC–melanoma interactions under shear conditions. In addition, endogenously produced IL-8 contributes to PMN-facilitated melanoma arrest on the EC through the CXC chemokine receptors 1 and 2 (CXCR1 and CXCR2) on PMN. These results provide new evidence for the complex role of hemodynamic forces, secreted chemokines and PMN–melanoma adhesion in the recruitment of metastatic cancer cells to the EC.     

Restoration of fluid balance after exercise-induced dehydration: effects of alcohol consumption

Shirreffs, Susan M., and Ronald J Maughan. Restorationof fluid balance after exercise-induced dehydration: effects of alcoholconsumption. J. Appl. Physiol. 83(4):1152-1158, 1997.The effect of alcohol consumption on therestoration of fluid and electrolyte balance after exercise-induceddehydration [2.01 ± 0.10% (SD) of body mass] wasinvestigated. Drinks containing 0, 1, 2, and 4% alcohol were consumedover 60 min beginning 30 min after the end of exercise; a differentbeverage was consumed in each of four trials. The volume consumed(2,212 ± 153 ml) was equivalent to 150% of body mass loss. Peakurine flow rate occurred later (P = 0.024) with the 4% beverage. The total volume of urine produced overthe 6 h after rehydration, although not different between trials(P = 0.307), tended to increase as thequantity of alcohol ingested increased. The increase in blood(P = 0.013) and plasma(P = 0.050) volume with rehydrationwas slower when the 4% beverage was consumed and did not increase tovalues significantly greater than the dehydrated level(P = 0.013 andP = 0.050 for blood volume and plasmavolume, respectively); generally, the increase was an inverse functionof the quantity of alcohol consumed. These results suggest that alcoholhas a negligible diuretic effect when consumed in dilute solution aftera moderate level of hypohydration induced by exercise in the heat.There appears to be no difference in recovery from dehydration whetherthe rehydration beverage is alcohol free or contains up to 2% alcohol,but drinks containing 4% alcohol tend to delay the recovery process.

     

Metabonomic studies on the physiological effects of acute and chronic psychological stress in Sprague-Dawley rats

The biochemical effects of acute and chronic psychological stress have been investigated in male Sprague-Dawley rats using a combination of 1H NMR spectral analysis of plasma and conventional hematological analyses. Animals were subjected to 35 consecutive days of 6-h sessions of stress, and following a 9 day break, were stressed for a further 6-h period. Plasma samples were collected at 0, 1, 3, and 6 h on days 1, 9, 21, 35, and 44, measured using 600 MHz 1H NMR spectroscopy, and analyzed by Principal Components Analysis. Time-dependent biochemical effects of psychological stress on a range of endogenous metabolites were evident and were correlated with the intensity of the stress response as defined by corticosterone and hematological parameters. Following acute stress, increases in the levels of glucose and ketone bodies, and decreases in the levels of acetate, alanine, isoleucine, lactate, leucine, valine, and lipoproteins, were observed. Chronic stress-induced increases in plasma levels of alanine, lactate (day 9), and leucine, valine, and choline (day 44) and decreases in acetate (day 9) and lipoprotein concentrations were observed. Positive correlations between plasma corticosterone level and glucose and glycerol, and between plasma lipoprotein concentrations and hemoglobin levels, were established using Projection to Latent Structures (PLS) analysis. This study indicates the potential of using NMR-based metabonomic strategies for the characterization of endogenous metabolic perturbations induced by psychological stressors and lifestyle choices.     

Water stress effects on maize: Carbohydrate metabolism of resistant and susceptible cultivars ofZea mays L.

Carbohydrate changea in drought resistant and susceptible cultivars ofZea mays L. were studied at two different stages under imposed water stress in water culture experiments. The gradual decline in total carbohydrates with increasing stress levels was observed. At the 1st leaf stage starch content of the resistant cv. Agati-76 was lower than that of susceptible cv. Vijay but the reducing and non-reducing sugar content was much higher. At the 3rd leaf stage starch content was similar in two cultivars but sugar content was higher in the resistant cv. Agati-76. Differential changes in root and shoot carbohydrates as affected by increasing levels of stress were noticed. Carbohydrate changes have been discussed in relation to drought resistance.     

Protective effect of calpain inhibitor N-acetyl-l-leucyl-l-leucyl-l-norleucinal on acute alcohol consumption related cardiomyopathy

Excessive alcohol consumption and alcoholism cause medical problems with high mortality and morbidity rates. In this study we aimed to decrease the alcohol related tissue damage by inhibiting calpain activation which plays an important role in apoptosis and necrosis, in rats with cardiomyopathy induced by acute alcohol consumption. Male Sprague–Dawley rats were separated into four groups (control, vehicle, alcohol and alcohol + inhibitor) with 10 rats in each. Control group received isocaloric maltose while vehicle group received isocaloric maltose with DMSO, and alcohol group received 8 g/kg absolute ethanol by gavage. Inhibitor group received 20 mg/kg calpain inhibitor 1 intraperitonally prior to alcohol administration. Calpain activities, cathepsin L levels and cytochrome c release rates were significantly increased in alcohol group compared to control group (p < 0.05). Serum CK MB and BNP levels of alcohol group were excessively increased compared to control group (respectively p < 0.001 and p < 0.01). Serum BNP levels of alcohol + inhibitor group were significantly (p < 0.05) decreased compared to alcohol group. In addition to these, histological evaluation of light microscope images and the results of DNA fragmentation and immunohistochemical caspase-3 activity results showed significant improvement of these parameters in alcohol + inhibitor group compared to alcohol group. Results of our biochemical and histological evaluation results revealed that the calpain inhibitor N-acetyl-leu-leu-norleucinal may have an ameliorating effect on acute alcohol consumption related cardiac tissue damage due to its effects on cell death pathways.     

Development of tolerance in rats to the hypothermic effects of D-amphetamine and apomorphine

Rats given d-amphetamine (15 mg/kg i.p.) or apomorphine (10 mg/kg i.p.) and placed in a cold environment (4°C) developed marked hypothermia. After daily injections of either drug for seven weeks, the maximal hypothermic responses to d-amphetamine or apomorphine were reduced to 72% and 19% of those obtained initially. Subsequent injection of ET-495, a central dopamine receptor stimulant, caused rectal temperature to decrease only 72% and 49% as much as in control animals. The hypothermic response to apomorphine was also depressed in d-amphetamine-treated animals. These observations suggest that the tolerance to the hypothermic effects of both d-amphetamine and apomorphine that develops is due at least in part to alterations in the sensitivity of dopamine receptors.     

The effects of chronic alcohol and vitamin E consumption on aging pigments and learning performance in mice

Chronic ethanol consumption further accelerates age-related impairment of shuttle box avoidance learning in mice. The hypothesis was tested that the behavioral impairment is a result of brain lipofuscin pigment deposition, which may be accelerated by ethanol consumption and prevented by the antioxidant effects of pharmacological doses of vitamin E. Feeding an ethanol-containing liquid diet for 5 months did not increase the lipofuscin content when compared with mice pair-fed a liquid diet containing isocaloric amounts of sucrose or standard solid laboratory food containing nutritionally adequate amounts of vitamin E. Supplementation of diets with vitamin E decreased brain lipofuscin content in all groups but failed to prevent the age- or ethanol-induced learning deficit. There was no effect of chronic ethanol consumption on brain weights, DNA, RNA, or protein content.It is concluded that the age-related impairment of avoidance learning is accelerated by chronic alcohol consumption. At the molecular level this acceleration is not caused by an increased brain lipofuscin deposition nor is it prevented by the antioxidant effects of vitamin E.     

Cholestasis following chronic alcohol consumption: Enhancement after an acute dose of chlorpromazine

Sprague-Dawley rats were pair-fed nutritionally adequate liquid diets containing either 36% of total calories as ethanol or isocaloric carbohydrates (controls) for 4 weeks. Compared to controls, chronic alcohol consumption leads to slightly increased serum activities of various hepatic enzymes including the alkaline phosphatase (AP). Chlorpromazine administered as a single dose 18 hours after ethanol with-drawal resulted within 18 hours in a significant increase of serum AP activity in rats fed ethanol chronically but not in their pair-fed controls. It is concluded that chronic alcohol consumption predisposes to cholestasis due to chlorpromazine.     

Npy deletion in an alcohol non-preferring rat model elicits differential effects on alcohol consumption and body weight

Neuropeptide Y(NPY) is widely expressed in the central nervous system and influences many physiological processes.It is located within the rat quantitative trait locus(QTL) for alcohol preference on chromosome 4.Alcohol-nonpreferring(NP) rats consume very little alcohol,but have significantly higher NPY expression in the brain than alcohol-preferring(P) rats.We capitalized on this phenotypic difference by creating an Npy knockout(KO) rat using the inbred NP background to evaluate NPY effects on alcohol consumption.Zinc finger nuclease(ZNF) technology was applied,resulting in a 26-bp deletion in the Npy gene.RT-PCR,Western blotting and immunohistochemistry confirmed the absence of Npy mRNA and protein in KO rats.Alcohol consumption was increased in Npy~(+/-) but not Npy~(-/-) rats,while Npy~(-/-) rats displayed significantly lower body weight when compared to Npy~(+/+) rats.In whole brain tissue,expression levels of Npy-related and other alcohol-associated genes,Npy1 r,Npy2r,Npy5 r,Agrp,Mc3 r,Mc4r,Crh and CrMr,were significantly greater in Npy~(-/-) rats,whereas Pome and Crhr2 expressions were highest in Npy~(+/-) rats.These findings suggest that the NPY-system works in close coordination with the melanocortin(MC) and corticotropin-releasing hormone(CRH) systems to modulate alcohol intake and body weight.