The role of testosterone in the development of experimental alcoholism

Sections

ABSTRACT
Introduction
Materials and methods
Results and discussion
Conclusions

Details

Author: G. N. LAKOZA , N. K. BARKOV
Pages: 41 to 48
Creation Date: 1980/01/01

The role of testosterone in the development of experimental alcoholism

G. N. LAKOZA Serbsky Institute of General and Forensic Psychiatry, Moscow, Union of Soviet Socialist Republics
N. K. BARKOV Serbsky Institute of General and Forensic Psychiatry, Moscow, Union of Soviet Socialist Republics

ABSTRACT

The hormonal effects of testosterone, progesterone and extradiol on voluntary preference of ethanol were investigated in experiments carried out on castrated male albino rats. It was observed that testosterone stimulated the development of ethanol preference, while the effects of progesterone and estradiol were significantly slower and less intensive. It was also observed that the androgenic action of testosterone was more important than its anabolic action in stimulating ethanol preference.

Introduction

Recently considerably increased attention has been paid to the effect of endocrinic disorders on the development of alcoholism. In this respect, depression of sexual function has been given much importance. Chronic alcoholism is known to have a negative effect on the sexual function, an effect which manifests itself in signs of feminization in men, masculinization in women, changes in sexual desire, impotence, sterility, pathologies in pregnancy and labour.

The consumption of alcohol causes a short-term decrease in testosterone level in the blood of healthy men [ 1] [ 2] ; testosterone in the blood of alcoholics is also often decreased [ 3] . At the same time, the fact that the degree of damage to sexual function of alcoholics in some cases coincides with increased levels of testosterone and androgen 17-OH in plasma is considered paradoxical [ 4] [ 5] . This may be connected with changes in testosterone metabolism [ 6] and estrogenic steroids [ 7] , which are often observable in alcoholic patients.

The foregoing indicates the role testosterone plays in the pathogenesis of chronic alcoholism, but it does not clarify the role of the male hormone in the etiology of this disease. This problem has never been given direct study. Data exist only on the possible initial damaging effect ethanol has on sexual glands [ 8] and on changes in the level of sex hormones at a stage of established alcoholism.

In this research the effect of testosterone, in comparison with the female hormones progesterone and estradiol, on the voluntary preference for ethanol was studied in experiments on castrated male albino rats. In addition, the action of testosterone analogues with different ratios of androgenic and anabolic components and antiandrogen cyproterone acetate was studied. This made it possible to analyse the correlation of androgenic and anabolic action of the male hormone in the development of experimental alcoholism.

The androgenic index of testosterone, which is defined as the ratio of androgenic to anabolic action, is equal to one. The anabolics nerobol and 19-nor-D-homotestosterone have lower androgenic indices than testosterone; the indices are 0.5 and 0.25 respectively [ 9] .

Materials and methods

In the experiments use was made of 96 male albino rats weighing 160-180 g with a stable low hormonal background. For this purpose they were castrated a month before the beginning of the experiment.

The experiment was carried out in two parts.

The first part of the experiment lasted seven weeks. Forty-eight rats were divided into four groups of 12 animals each. The first group served as a control. Hormones were injected daily to rats of the second, third and fourth groups; the animals of the second group received testosterone proportionate (1 mg/kg), the third group progesterone (1 mg/kg), and the fourth group estradiol benzoate (1 μg/kg) during the first three and a half weeks. During the following three and a half weeks the doses of hormones were increased threefold, and all hormones were injected subcutaneously once a week in oil solutions.

In the second part of the experiment, which lasted 10 weeks, the effect of testosterone propionate was studied in comparison with the anabolics nerobol (Gedeon Richter Co.) and 19-nor-D-homotestosterone (the preparation was synthesized at the Institute of Bioorganic Chemistry, Academy of Sciences, USSR) on four groups of 12 animals each. During the first four weeks of this part of the experiment, all hormones were injected in doses of 1 mg/kg, the testosterone propionate in oil solution once a week, the nerobol and 19-nor-D-homotestosterone, in aqueous solution daily. During the following six weeks all doses of hormones were increased threefold.

The therapeutic effect of cyproterone acetate was studied on a group of rats which received testosterone propionate and could freely choose between water and 8 per cent ethanol solution. Cyproterone acetate SH-80714 (Schoring Co.) in the dose of 10 mg/kg a day was injected intraperitoneally in the course of 10 days.

Alcoholization of animals was carried out under the scheme of Barkov and Nesmelov [ 10] , which ensures compulsory alcoholization of rats by means of intraperitoneal injections of 5 per cent ethanol solution for two weeks. Subsequently, the animals could freely choose between water and 8 per cent ethanol solution. The rats were put into experimental cells equipped with two measuring bottles for three hours every day. The animals were kept on dry standard fodder.

The speed and degree of preference was determined in the situation of free choice between 8 per cent ethanol solution and water. The speed of development of preference was determined by the number of animals in the group preferring ethanol solution to water. The degree of preference was estimated in relative units, calculated by taking the ratio of the average amount of alcohol consumed by one rat per day to the amount of water consumed. In both cases only those animals were taken into consideration whose intake of ethanol solution was no less than twice their intake water.

The significance of experimental data was assessed according to the criterion t at p = 0.05.

Results and discussion

In figure I, experimental data are presented on the effect of male and female hormones on the average speed (A) and degree (B) of development of preference for ethanol in male albino rats during the period of free choice between water and alcohol (third to seventh week of the experiment).

The results of the two-week compulsory alcoholization of animals by means of intraperitoneal injections of ethanol was that, by the third week of the experiment, in the situation of free choice between water and 8 per cent ethanol solution, a rather high percentage of rats (30 to 40 per cent) preferring ethanol to water could be observed in all groups.

Further observation showed that, as the experiment continued, the number of rats preferring ethanol to water increased in all experimental groups. But the highest number, in comparison with the control group, was in the second ("testosterone") group (in the fourth and sixth weeks the number was statistically significant as compared with the controls).

Preference for ethanol consumption in castrated animals receiving female hormones developed slower and less intensively than in rats receiving testosterone.

Statistically significant differences in the speed of development of preference in those animals receiving progesterone and estradiol, in comparison with the controls, were not observed in the course of the experiment.

The results of the study on the effect of sex hormones on the degree of preference for ethanol in castrated male albino rats coincide in many respects with the data on the speed of its development.

In this respect, the group of rats receiving testosterone differed greatly from the other groups. By the fourth week of the experiment the rats in this group were consuming a volume of 8 per cent ethanol solution which was 14 times the volume of consumed water.

In the sixth and seventh weeks the volume of consumed ethanol was respectively 45 and 25 times the volume of consumed water.

The increase in preference for ethanol consumption in the group of rats receiving estradiol and progesterone was as low as in the group of castrated rats which received no hormones and equalled 5-8 relative units.

Figure 1 Effect of sex hormones on the speed (A) and degree (B) of development of ethanol preference in castrated male rats. The arrows show where differences are statistically significant (p = 0.05).

Full size image: 29 kB, Figure 1 Effect of sex hormones on the speed (A) and degree (B) of development of ethanol preference in castrated male rats

Thus, the experiments on castrated male rats showed that testosterone propionate produced a selective stimulating effect on the speed and degree of development of addiction to ethanol in comparison with the female hormones progesterone and estradiol.

In fact, estradiol and progesterone had little influence on this process, and even showed a tendency towards making it slower.

The results of the second part of the experiment, the series of tests on the effect of testosterone and its analogues nerobol and 19-nor-D-homotestosterone on the speed and degree of the development of preference for ethanol, are presented in figure II.

This series of tests also demonstrated that compulsory alcoholization resulted in rapid alcoholization of rats in the situation of free choice between water and 8 per cent ethanol solution.

The number of rats preferring ethanol to water increased in all groups. The number was highest in the group of rats receiving testosterone when compared with the controls, whereas it was lowest in the group of animals receiving 19-nor-D-homotestosterone-the substance having the lowest androgenic index. It should be noted that this difference was not statistically significant.

Thus the substances having high androgenic index, i.e. testosterone propionate and nerobol, unlike 19-nor-D-homotestosterone, appear to stimulate the preference for ethanol sharply. Preference for ethanol consumption increased up to 50 relative units under the influence of testosterone propionate.

Preference for ethanol consumption in animals receiving 19-nor-D-homotestosterone varied from 2 to 10 relative units and was even less pronounced than in the control group.

The comparison of obtained data allows us to conclude that the preference for ethanol consumption in male albino rats induced by testosterone and its analogues is directly dependent on the ratio of their androgenic properties to anabolic ones, i.e. on the androgenic index.

The role of the androgenic component of testosterone propionate in the stimulation of experimental rat alcoholism was further analysed in tests with antiandrogen cyproterone acetate, which was administered with a therapeutic aim.

Antiandrogen was found to produce a sharp declining effect on the experimental alcoholism created in castrated male albino rats receiving testosterone.

These data also confirmed the important role androgenic properties of testosterone played in the stimulation of experimental alcoholism.

The data obtained concerning the selective stimulating effect of testosterone propionate in comparison with female hormones on the development of experimental alcoholism seem unexpected, because the castrated rats receiving testosterone substitution therapy were supposed to be more resistant to any intoxication, including also alcoholic intoxication.

Rubin and co-workers found that ethanol was capable of significantly increasing the activity of the microsomal 5 α-testosterone-reductase enzyme, which could convert testosterone into its more active metabolite, dihydrotestosterone [ 11] .

It is possible that the increase in the activity of 5α-testosterone reductase, functioning on the level of alcoholdehydrogenase, changes the redox-state of the liver. The latter is known to be one of the important mechanisms of the effect of ethanol on liver metabolism in chronic alcoholics [ 12] .

FigureII Effect of testosterone and its analogues on the speed (A) and degree (B) of the development of ethanol preference in castrated male rats. The arrows show where differences are statistically significant (p = 0.05).

Full size image: 32 kB, FigureII Effect of testosterone and its analogues on the speed (A) and degree (B) of the development of ethanol preference in castrated male rats

The study of the mechanism of the testosterone stimulating effect on the development of experimental alcoholism allows us to conclude that the androgenic component plays a more important role in this phenomenon than does the anabolic component.

These data on the motivation for ethanol consumption are of interest and may have practical implications in the determined search for anti-alcoholic hormonal drugs.

Conclusions

  1. Testosterone stimulates the development of ethanol preference in castrated male albino rats, whereas estradiol and progesterone have significantly less effect.

  2. The androgenic component of testosterone action is more important than the anabolic component in the stimulation of experimental alcoholism.

References

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