Letter: A simple screening test for drugs of potential use in ethanol withdrawal

Effect of two iron-chelators, desferrioxamine and diethylenetriaminepentaacetic acid, on the development of tolerance to the physical dependence on ethanol in mice

Physical dependence on ethanol was induced in mice by exposing the animals to increasing concentrations of ethanol vapor for a period of 9 days. The degree of dependence was assessed by subjective scoring of a characteristic behavioral withdrawal syndrome upon cessation of ethanol administration. The daily administration of desferrioxamine (350 mg/kg, i.p.) or of diethylenetriaminepentaacetic acid (200 mg/kg, i.p.) during the ethanol treatment period reduced by 50% the behavioral withdrawal score. On the other hand, an iron-load of 250 mg/kg administered once prior to ethanol treatment and once during ethanol exposure caused a significant increase in the withdrawal score. While the degree of dependence was significantly lowered by the iron chelators, the state of tolerance after chronic ethanol treatment was not altered by these agents. However, the capacity of these ethanol-treated animals to develop rapid functional tolerance at termination of the chronic ethanol exposure was significantly enhanced by desferrioxamine and diethylenetriaminepentaacetic acid. The results are discussed in view of possible role of iron-induced peroxidation of neuronal membrane lipids in the development of tolerance to and dependence on, ethanol.

The effect of neuroleptics, tranquillizers, narcotics, antidepressants and anticonvulsive drugs on the alterations of mouse behaviour caused by acetaldehyde

In a study of the effect of 26 psychoactive drugs on the complex of mouse behaviour changes caused by acetaldehyde it was found that tranquillizers, hypnotics, sodium oxybutyrate and ethanol are the most efficient. The differences in teh drug effects were determined by a tan alpha criterion. Antidepressants and neuroleptics have equal tan alpha, whereas narcotics, anti-convulsive drugs and tranquillizers all have similar tan alpha, but greater than that of the antidepressants and neuroleptics. A direct dose/effect relationship was found to exist for all the drugs investigated except for neuroleptics and antidepressants. For the latter drugs an increase in dose is followed by an increased effect, which, however, decreases on further increase of the dose. The convulsive syndrome is completely abolished only by tranquillizers and narcotics. Our results are quite in agreement with clinical data about the effectiveness of psychoactive drugs in the treatment of the alcohol abstinence syndrome. The method can be used not only for screening purposes, but also to define the specificity in the action of antialcoholic drugs.

A method for bioassay of physical dependence on sedative drugs in dog

A method for an economical bioassay of physical dependence on sedatives is presented. Dogs maintained on sodium pentobarbital (200 mg/kg/24 h i.v.) were given periodic graded reductions in maintenance dose, and subscales for measuring signs of abstinence were developed. Using these subscales the relative potencies compared with sodium pentobarbital were determined for sodium secobarbital (RP = 0.85) and methaqualone (RP = 0.14). Sodium thiopental and methaqualone were assayed and found to be equipotent (RP = 0.96) in reducing the signs of abstinence from sodium pentobarbital. The occurrence of convulsions, during periods of complete reduction of the maintenance drug, became less frequent the longer the dogs had been maintained on a constant dose of sodium pentobarbital.

Preparation and pharmacological activity of the condensation product of adrenaline with acetaldehyde

In vitro incubation of adrenaline with acetaldehyde resulted in the formation of an amorphous product (MA 3) which gave origin to two spots on chromatography plates. Preparative TLC allowed us to separate the corresponding substances, MA 4 and MA 5. Gas chromatography-mass spectrometry, ultraviolet and infrared spectra of MA 4 agree with the structure corresponding to 1,2-dimethyl-4,6,7-trihydroxy-1,2,3,4-tetrahydroisoquinoline. MA 5 is very unstable and was not further characterized. Pharmacological experiments were carried out with MA 3 and MA 4 (and in some cases, MA 5) on isolated saphenous vein strips and isolated guinea-pig atria; responses of the nictitating membrane, blood pressure and hind-limb perfusion pressure were obtained in the anaesthetized dog. There were only quantitative differences between the effects of MA 3, MA 4 and MA 5 (where tested). Therefore, these effects are described as effects of TIQs (tetrahydroisoquinolines). TIQs contracted isolated saphenous vein strips, behaving as total agonists; the dose-response curves were displaced to the right by phentolamine and to the left by cocaine (potentiation factor: 2.7 +/- 0.1). In the dog, contractions of the nictitating membrane, rises of blood pressure and of the perfusion pressure (after i.a. injection) were observed. On isolated guinea-pig atria, weak beta adrenergic receptor activation was found. With higher concentrations, beta receptor blockade was observed, for both cardiac and vascular smooth muscle receptors. The effects of TIQs were short-lasting, showing that a rapid inactivation occured both in vitro and in vivo; neuronal uptake appears to play an important role in inactivation, since cocaine was able to block about 70% of the inactivation capacity of isolated vein strips. The effects of nerve stimulation on the vein strips or on the nictitating membrane were reduced by TIQs; however, this did not affect responses to noradrenaline and enhanced those to tyramine or DMPP. Simultaneously with reduction of the effects of electrical stimulation, blockade of inactivation of endogenous and exogenous noradrenaline was induced by TIQs. Marked depletion of noradrenaline levels in the heart, hypothalamus and aorta of the guinea pig was caused by MA 3 (1-3 mg/kg). It is concluded that the condensation products of adrenaline with acetaldehyde are not devoid of pharmacological activity, are taken up by adrenergic nerve terminals and may act as false transmitters. The similarity of effects of TIQs and acetaldehyde suggests that formation of TIQs may occur in vivo, after acetaldehyde (or ethanol) administration, both in the adrenal gland and in sympathetic nerve terminals. These TIQ alkaloids could play an important role in alcoholic intoxication and in the ethanol withdrawal syndrome.