Jorge Mardones

Experimentally Induced Changes in the Free Selection of Ethanol

Publisher Summary The amount of ethanol consumed under free-choice conditions varies in animals. Smaller animals such as mice metabolize ethanol faster, and this may correlate with their higher voluntary intake. Individual variation in the consumption of ethanol is a genetic factor in rats, and these have been inbred to produce drinker and nondrinker strains. No metabolic differences between these two strains have been found. Single deprivation of most of the water-soluble vitamins increases ethanol consumption. Thioctic acid or glutamine decreases ethanol intake. When sugar solution or fat emulsion is offered as a third choice, the intake of ethanol decreases, and this is correlated with the extra calories provided by the third choice. Saccharin after sugar solution also decreases ethanol intake. No increase in ethanol intake occurs in rats after either forced or free-choice ethanol administration for long periods. Of the endocrine influences reported, the thyroid effect is questionable, gonads are noncontributory, and the adrenal cortex has been insufficiently studied. Insulin and oral antidiabetic drugs increase and alloxan or pancreatectomy decreases ethanol intake. Adrenalectomy also decreases voluntary intake. Stimulant, ataractic, or psychotomimetic drugs do not change ethanol intake. Disulfiram and related drugs decrease ethanol intake. Drugs, which produce liver damage, definitely increase ethanol intake. Methionine sulfoximine produces an increase and ultimately a decrease in ethanol intake. These studies are compared to chronic alcoholism in humans.

Effects of Aminotriazole on Ethanol, Water, and Food Intake and on Brain Catalase in UChA and UChB Rats

Aminotriazole (AT), a catalase inhibitor, was administered to UChA (low ethanol consumer) and UChB (high ethanol consumer) rats. Ethanol, water, and solid food intake were measured during basic, treatment, and posttreatment periods. The effects of AT on brain catalase activity and acetaldehyde recovered during incubation of brain homogenates with ethanol were also studied in rats of both strains. Results showed that AT decreased voluntary ethanol intake in UChB rats, and also diminished the consumption of food by rats of both strains. No strain difference in brain catalase activity and acetaldehyde recovered during ethanol incubation was observed. The results suggest that AT effect on ethanol consumption is secondary to a reduction in the appetite for calories and not related to its catalase blocking effect.

Effect of 3-amino-1,2,4-triazole on narcosis time and lethality of ethanol in UChA rats

The capacity of rat brain homogenates to oxidize ethanol by catalase peroxidative system, previously reported, was reevaluated in experiments using lower ethanol concentration, showing that the effect of this system can be observed even with a concentration of 50 mM, equivalent to non lethal blood level. The involvement of catalase was confirmed by its blocking by aminotriazole (AT) or methanol but not by pyrazole or butanol. Evidence for a functional role of ethanol oxidation by brain catalase in the action of this substance was given by the fact that rats pretreated with AT (1 g/kg IP) exhibited a significant shorter narcosis than untreated controls, strongly suggesting the mediation of acetaldehyde in this effect. Previous results with doses of 60 mmole/kg IP were confirmed with 70 mmole/kg IP, but not with 90 mmole/kg IP. A significant prolonging of narcosis time was observed when AT was administered after any of these doses by an unknown mechanism. Furthermore it was observed that AT pretreatment reduced significantly the lethal effect of 110 mmole/kg IP ethanol; but when AT was given after ethanol (90 mmole/kg IP) it enhanced the lethality. These results suggest that catalase peroxidative pathway might play a role not only in narcosis time but also in ethanol toxicity.

Effects of serotonin uptake blockers and of 5-hydroxytryptophan on the voluntary consumption of ethanol, water and solid food by UChA and UChB rats

The effects of zimelidine, fluvoxamine, and citalopram (serotonin uptake blockers), as well as those of 5-hydroxytryptophan (serotonin precursor), on the voluntary consumption of 10% ethanol solution, distilled water and solid food were tested in UChA (genetically low ethanol consumer) and UChB (genetically high ethanol consumer) rats. Since it is well known that drugs which stimulate central serotonergic synapses decrease food and water intake, the data concerning the difference of the respective consumption during the treatment period and the pretreatment one were analysed with a method previously proposed (Alcohol 5:15-19; 1988) to recognize specific effects on ethanol intake. The results showed that while the decrease of ethanol consumption induced by the three serotonin uptake blockers appeared not to be specific of ethanol, the effects of 5-hydroxytryptophan in UChB rats satisfy the criteria for being considered as an expression of a decrease of the specific appetite--or increase satiety--for ethanol. Experimental results cannot help in the explanation of this difference.

Influence of sex difference and hormones on elastine and collagen in the aorta of chickens.

Collagen and elastine of the aorta were estimated in normal chickens of both sexes in cockerels, gonadectomized or treated with estradiol, and in hens treated with testosterone. The results showed that collagen and elastine were significantly higher in males than in females. Gonadectomy in males decreased significantly the content of collagen and elastine, so that the values became similar to those observed in females. The treatment of males with estradiol lowered the collagen and elastine content to values similar to those observed in females and in gonadectomized males. The treatment of females with testosterone increased significantly the collagen and elastine content of the aorta to levels similar to those observed in males.

Genetic differences in tolerance to ethanol: a study in UChA and UChB rats.

The development of tolerance to ethanol was studied in two strains of rats, UChA (low ethanol consumer) and UChB (high ethanol consumer), by the sleeping time test. Marked tolerance (perhaps both metabolic and tissue) appeared in UChA rats, while only a slight tissue tolerance and not a metabolic one appeared in the UChB rats, when they were offered 10% ethanol as the sole fluid during 31 days (p less than 0.001). In UChA, but not in the UChB rats, the chronic treatment with ethanol induced tolerance to pentobarbital as shown by the same test.

A method for recognizing specific effects on ethanol intake by experimental animals

A method of mathematical treatment of data concerning changes in voluntary consumption of ethanol solution, water and solid food, induced by experimental treatments in animals, in order to recognize effects on mechanisms involved in specific appetite and satiety for calories, water and ethanol is proposed. The need of such method arises from the fact that several experimental treatments tested by the effects on ethanol consumption alter at the same time the appetite or satiety for calories and/or for water, as well as ingestive behavior. The results of testing the method with the data obtained by treatment of UChA and UChB rats with disulfiram or cyanamide were consistent with the expected ones.

Effect of 3-amino-1,2,4-triazole pretreatment on ethanol blood levels after intraperitoneal administration.

Aminotriazole (1 g/kg IP) pretreatment resulted in higher ethanol blood levels during the first hour after 90 mmole/kg IP ethanol administration and at 1 hour after when rats received 60 mmole/kg IP, than the respective controls receiving the same doses of ethanol. No difference in the blood levels at time higher than 1 hour were observed, in spite of the fact that the inhibitory effect of aminotriazole lasted more than 7 hours. These results are consistent with the idea that hepatic catalase may play a significant role in liver first pass effect when portal blood levels are expected to be rather high, but not when distribution balance is established.

Effects of bromocriptine on the voluntary consumption of ethanol, water, and solid food by UChA and UChB rats

The effect of bromocriptine (stimulant of dopaminergic D2 receptors) on the daily consumption of 10% v/v ethanol solution, distilled water, and solid food, under free-choice conditions, was measured in nine genetically low (UChA) and six high ethanol consumer (UChB) adult female rats. Animals were housed in individual cages and maintained at room temperature of 23 +/- 1 degree C and with 12/12 h dark/light rhythm. The consumption of ethanol solution, water, and solid food was measured in pretreatment, treatment, and posttreatment periods of 3 days (Tuesday through Thursday) of 3 consecutive weeks. During the treatment period rats received daily a single oral dose of 8 mg of bromocriptine mesylate (Sandoz) suspended in 1 ml of water per kg of body weight. Data analysis was performed with a method previously reported, which allows to recognize specific effect of ethanol intake, depurated from the effects on calories and/or water consumption. Results showed that all UChB rats decreased significantly and specifically the consumption of ethanol solution during the treatment period compared to the pretreatment period (mean: -58 +/- 15%) and recovered the pretreatment consumption in the posttreatment period, without significant changes in the consumption of food and/or total water. The only significant change observed in UChA rats was a decrease of the consumption of solid food (mean: -15 +/- 5%). Results are consistent with the idea that a dopaminergic D2 synapsis participates in the neural network responsible for satiation with ethanol.

EVIDENCE OF GENETIC FACTORS IN THE APPETITE FOR ALCOHOL AND ALCOHOLISM

Varela’ postulated that the appetite for alcohol observed in human beings could be classified as physiological, pharmacological, or pathological. It seems that physiological appetite is related to the caloric value of ethanol. People experiencing this kind of appetite do not look for the effect of alcohol on the central nervous system (CNS), with the result that they drink in amounts and conditions that do not allow an increase of blood alcohol to levels affecting behavior. Alcohol consumption on the part of experimental animals, specially rats and mice, has been considered to be caused by physiological a p ~ e t i t e . ~ . ~ Individuals with pharmacological appetite for alcohol clearly want to experience the effects of this drug on the CNS, inducing a change of mood and even a loss of consciousness. Some of these individuals look only for alcoholinduced euphoria, but others want to be alienated through inebriety. Animal models of this kind of appetite are the Masserman cats as well as monkeys allowed to self-inject ethanol solutions. Pathological appetite is defined by Varela as that induced by physical dependence on alcohol, which is expressed by the symptoms characterizing the forms denominated gamma and delta alcoholism by Je l l i ne~k .~ The presence of genetic factors playing an important role in the physiological appetite for alcohol observed in rats and mice can be considered as a very wellestablished fact. The data are from ‘‘drinker” and “nondrinker” strains of rats obtained by artificial selection in the University of Chile (UChA and UChB)5 and in the ALKO laboratories in Helsinki (AA and ANA)6 as well as by the different voluntary intake of alcohol observed in several inbreed strains of mice7. The idea of genetic factors in alcoholism is a very old one; but data concerning it have been accumulating only in recent years. The evidence coming from studies of twins or half-siblings is discussed by other authors in this symposium. I will therefore limit myself to the discussion of the eventual finding of an X-linked factor in alcoholism. The idea of the presence of such a factor arose from the discovery by CruzCokes of a highly significant association between alcoholic liver cirrhosis and color blindness. The association of color blindness with alcoholism independent of liver damage was observed afterwards by Cruz-Coke and Varelaeg In both studies, color vision was tested by the Hardy-Rand-Ritter plates (HRR) and generally classified as undetermined, since the most frequent failure was in the plate 3 of this test. Using a more accurate method, the Farnsworth Munsell 100-hue test (FM 100) Varela and colleagueslo confirmed this association and were able to establish that the color-discrimination disturbance was located in the blue-yellow and bluegreen zone of the spectrum. The association between color blindness and liver cirrhosis was confirmed by Fialkow and co-workers,lI who considered this alteration as secondary to the liver damage, since some of the patients who failed in plate 3 of the HRR test were able to see it after recovery.