Acquired myasthenia gravis and cholangiocellular carcinoma in a dog

Acquired myasthenia gravis and cholangiocellular carcinoma were diagnosed in a 7-year-old English Setter referred because of forelimb lameness, exercise-induced weakness, and fever. Three months earlier, the dog had had a pleuropulmonary infection caused by a Fusobacterium sp. The concurrent development of myasthenia gravis and cholangiocellular carcinoma in this dog may be explained by a paraneoplastic syndrome, although it is unproven. The cholangiocellular carcinoma may have possessed an acetylcholine receptor-like antigen on the tumor surface, which induced autoantibodies to cross-react with acetylcholine receptors at the neuromuscular junction.

Social models of drinking behavior in animals. The importance of individual differences

Although certain social environments clearly facilitate alcohol intake in humans, the role of social factors in alcohol consumption by animals is less clear. While social housing conditions such as crowding and isolation increase alcohol consumption in animals, in both cases this is mediated by heightened stress. Increases in social tension increase alcohol consumption in social groups of animals, but the literature is extremely variable in reports of how dominance correlates with alcohol consumption. Alcohol administration has biphasic effects on social behavior of animals similar to its biphasic effects on activity levels. We report a novel, social animal model of alcoholism. Rats raised over prolonged periods in highly enriched, social colony environments develop a variety of rhythms of alcohol consumption. But in each colony, only a few animals develop into extreme overconsumers of alcohol, and the proportion of colony-housed animals that develop such excessive alcohol -consumption habits is similar to the proportion of humans with alcohol problems. These overconsumers of alcohol from a rat colony show a variety of alterations in behavior, including chronic inactivity and low dominance standing. They represent a novel, voluntary animal model of social alcoholism.

Increased consumption of diazepam during continuous amphetamine administration

Previous investigations in our laboratory have demonstrated that after implantation of slow-release d-amphetamine pellets, rats with free access to water and a 10% ethanol solution selectively increase their consumption of the ethanol solution. We now report that this d-amphetamine treatment produces a similar increase in drinking of a benzodiazepine (diazepam) solution. Female albino rats were given free access to water and a 0.060 mg/ml diazepam solution and fluid intake was recorded every two days. The baseline consumption of diazepam averaged 25% of the total daily fluid intake. After d-amphetamine pellet implantation, rats increased their diazepam consumption to an average of 48% of total fluid intake, whereas rats implanted with control pellets containing vehicle only showed no change in diazepam drinking.

Ethanol intake increases during continuous administration of amphetamine and nicotine, but not several other drugs

Groups of rats, acclimated to drinking both water and 10% v/v ethanol were implanted with a variety of slow-release devices containing d-amphetamine (d-amp), nicotine, caffeine, phencyclidine (PCP), secobarbital, LSD, mescaline or haloperidol. Ethanol intake was elevated only during treatment with d-amp or nicotine; none of the other drugs affected ethanol consumption even though the amounts of all drugs released were pharmacologically sufficient to affect behavior. Nicotine treated rats were not simply seeking calories provided by the EtOH solution, since nicotine treatment did not enhance intake of a distinctively flavored solution isocaloric to 10% ethanol. These results support a self-medication model of ethanol intake.

Low-level continuous amphetamine administration selectively increases alcohol consumption

Rats dramatically increased alcohol preference following the subcutaneous implantation of slow-release d-amphetamine pellets, so long as access to ethanol was withheld during the initial 6 days after pellet implantation. This increased ethanol preference was not due to a conditioned flavor aversion, nor to increased caloric intake, nor to alcohol deprivation. d-Amphetamine must be administered in a continuous fashion in order to obtain this effect, for daily injections of the same amount of the drug did not increase ethanol intake. This increased ethanol preference is interpreted as self-medication. This effect may provide a new animal model for the tension-reduction theory of ethanol intake.