Cross-physical dependence of several drugs in methaqualone-dependent rats

DARK Classics in Chemical Neuroscience: Methaqualone

Commonly known as "Quaaludes," methaqualone (1) is a sedative-hypnotic medication, with effects resembling barbiturates and other downers, that exerts its effects through modulation of γ-aminobutyric acid type A receptors (GABA_AR). Following the discovery of the sedative and euphoric effects of methaqualone (1), it was quickly adopted by pharmaceutical companies and promoted by clinicians around the world as a "safe" sleeping pill option, and for a period it was available over the counter. The popularity of methaqualone (1) soared worldwide, and many people began to use it recreationally for its sedative-hypnotic-like psychoactive effects. Not long after its introduction, many individuals began to misuse the drug leading to overdoses and drug dependence which brought to light methaqualone's (1) addictive nature. In this review, the background, synthesis, pharmacology, metabolism, and pharmacokinetics of methaqualone (1) will be covered along with its discovery, history, and the derivatives that are currently available around the world through manufacture in clandestine laboratories.

Genetic differences in the development of physical dependence upon diazepam in Lewis and Fischer 344 inbred rat strains

The purpose of the present study was to investigate physical dependence upon diazepam systematically in two inbred strains of rats, Lewis (LEW) and Fischer 344 (F344). Rats were chronically fed food containing diazepam on an escalating drug dosage schedule, from 1 and 2 to 12 mg/g of food, over a period of 30 days. During treatment, the growth curve in LEW and F344 rats was suppressed compared with the respective controls. Motor incoordination was evaluated by a rotarod performance test. The ranking of the motor incoordination during the final concentration of diazepam was as follows: F344 greater than LEW. After substitution of normal food for the diazepam-admixed food, various signs of diazepam withdrawal occurred 16-120 h later. These signs included vocalization, irritability, muscle rigidity, ear-twitching, Straub's tail, piloerection, fascicular twitch, tremor, convulsion, and death. The incidences of vocalization, ear-twitching, piloerection, and tremor in F344 were significantly higher than those in LEW rats. Furthermore, two of six F344 rats showed spontaneous convulsions and one rat died of convulsions. Overall withdrawal scores were significantly greater in F344 (16.0) than in LEW (6.3) rats. These results suggest that diazepam withdrawal severity is strongly influenced by genetic factors, and F344 rats are highly susceptible to dependence upon benzodiazepines.

Substitution of psychoactive drugs in pentobarbital-dependent rats

The substitution of either bromazepam, diazepam, methaqualone, mazindol, nortriptyline or bupropion for pentobarbital, in dependent rats, was assessed using a continuous drug infusion method. Male, Sprague-Dawley rats were made dependent on pentobarbital during 12 days of continuous, intraperitoneal, pentobarbital infusion. On Day 13, pentobarbital was replaced with either saline, vehicle, or one of the drugs of interest and rats were infused for 24 h. On Day 14, all rats were infused, for 24 h, with saline. Changes in both body weight and behavioral indices of withdrawal were assessed during Day 13 and 14. It was observed that bromazepam and methaqualone substituted for pentobarbital in a dose-dependent fashion. Diazepam also substituted in pentobarbital dependent rats but, inexplicably, the low dose of diazepam provided better substitution than did the higher dose. On the other hand, neither mazindol or nortriptyline substituted for pentobarbital and there was a tendency for exacerbation of the withdrawal signs. Finally, it was noted that the low dose of bupropion appeared to decrease the severity of the withdrawal symptoms. The data supports the view that the substitution of compounds for pentobarbital, in dependent rats, is limited to those compounds which, presumably, possess similar mechanisms of action in the CNS.