Edward Majchrowicz

Induction of physical dependence upon ethanol and the associated behavioral changes in rats

This paper reports findings relative to a simple, rapid and reproducible technique for the induction of physical dependence upon ethanol in the rat. The dependence was induced by intragastric intubation of 20% (w/v) ethanol solutions at 9–15 g/kg in 3–5 fractional doses daily for 4 days, maintaining blood ethanol concentrations above a threshold level sufficient to sustain observable sedation throughout the entire period of intubation. Two phases were distinguished during the withdrawal period: 1. Prodromal detoxication, characterized by a spectrum of signs and responses of diminishing severity, related to the decline in blood ethanol concentrations (mg/dl): death, >640; coma, 780–460; loss of righting reflex, 640–440; ataxia 3–1, 570–250; sedation, 340–190; neutrality, 220–130; 2. Ethanol dependence, characterized by a spectrum of withdrawal signs and reactions of progressively increasing severity as blood ehtanol concentration approached 100mg/dl: hyperactivity, tremors, akinesia, spastic rigidity, and induced and spontaneous convulsions. A rapid succession of two diverse clusters of signs and reactions represents a reversal of the central nervous system function from the extremes of ethanol intoxication (CNS depression) to the extremes of ethanol dependence (CNS hyperexcitability) during the withdrawal period. Both extremes may terminate in death.

Temporal Relationship of the Induction of Tolerance and Physical Dependence after Continuous Intoxication with Maximum Tolerable Doses of Ethanol in Rats.

Rats were treated by intragastric intubation of a 20% ethanol solution in doses of 9–15 g/kg in 3–5 fractions for 1–7 days. Both tolerance and physical dependence were demonstrated after this treatment with the maximum tolerable doses to only a few days. Tolerance was assessed by signs of severity of intoxication: coma, loss of righting reflex, ataxia-3, ataxia-2, ataxia-1, sedation, and neutrality. During withdrawal, as blood ethanol concentrations approached 100 mg/dl the ethanol dependence phase was characterized by the onset of signs and responses of progressive severity: hyperactivity, tremors, spastic rigidity, and spontaneous convulsive seizures. A significant degree of tolerance was demonstrated for all signs of intoxication after 4 days of treatment, but did not reach maximum level even after 7 days. The severity of the withdrawal reactions intensified progressively to a maximum intensity after 4 days of treatment when as many as 72% of animals exhibited severe withdrawal signs and reactions including convulsive seizures. These different time courses suggest that tolerance and physical dependence are mediated through different mechanisms.

Blood Concentrations of Acetaldehyde and Ethanol in Chronic Alcoholics

Fifteen adult male alcoholic volunteers were studied before, during, and after a 10- to 15-day period of experimentally induced intoxication. Blood acetaldehyde concentrations ranged from 0.11 to 0.15 and from 0.04 to 0.08 milligrams per 100 milliliters when blood ethanol concentrations ranged from 1 to 400 milligrams per 100 milliliters after consumption of bourbon or grain ethanol, respectively. No dose or dose-time relationships were found between blood ethanol concentrations and blood acetaldehyde concentrations during any phase of this study.

Effects of ethanol administration on parameters of immunocompetency in rats.

Ethanol administered to rats intragastrically in doses sufficient to cause dependency resulted in a rapid cell loss from the thymus and spleen. Cell loss from the peripheral blood was due primarily to a loss of lymphocytes, but a concomitant granulocytosis resulted in only small changes in the total leukocyte count. Lymphocyte proliferation to both T‐ and B‐cell mitogens was severely compromised by ethanol treatment. The cell loss and functional lymphocyte impairment also occurred at half the ethanol dose required to induce dependency. Although cell numbers recovered relatively quickly after ethanol withdrawal, lymphocyte function, as measured by proliferation, recovered more slowly. Ethanol administration before or during immunization with sheep erythrocytes resulted in an impairment in the ability of animals to respond with a primary immune response to this antigen. These data suggest that ethanol given in quantities sufficient to produce dependence impairs in vitro and in vivo parameters of immunocompetency.

Adrenal function and alcoholism. II. Catecholamines.

&NA; Urinary excretion of catecholamines and their metabolites were determined in alcoholic subjects during chronic ethanol ingestion and after alcohol withdrawal. A dose response relationship was found between magnitude of blood alcohol levels and increased excretion of epinephrine, metanephrine, norepinephrine and noremetanephrine. Maximal excretion of epinephrine occurred when subjects developed withdrawal signs and symptoms after they had stopped drinking. A significant decrease in excretion of VMA and a concomitant increase in MHPG excretion occurred when subjects were drinking. These data indicate that chronic ethanol ingestion is associated with both stimulation of adrenergic activity and alteration in pathways of catecholamine catabolism.

Changes in cortical synaptosomal plasma membrane fluidity and composition in ethanol-dependent rats

Synaptosomal plasma membranes (SPM) were examined from the following four groups of rats: controls; rats acutely treated with single doses of ethanol; a prodromaldetoxication group (dependent-intoxicated); rats undergoing overt ethanol-withdrawal syndrome. Estimates of the apparent microviscosity of SPM over a range of temperatures indicated that temperature-induced changes in SPM fluidity were smaller during the prodromal detoxication phase. The cholesterol: phospholipid molar ratio significantly increased in SPM from the prodromal-phase rats, but to a lesser extent in rats undergoing ethanol withdrawal syndrome. The fatty acid content of SPM phospholipids was not significantly changed in any of the treatment groups. Addition of cholesterol in vitro to control membranes altered the apparent microviscosity similarly to the changes found in SPM of ethanol-dependent rats. These studies suggest that physical dependence upon ethanol may be related to changes in synaptosomal membrane composition and viscosity.

Acute ethanol administration selectively alters localized cerebral glucose metabolism

The effects of acute ethanol administration on glucose utilization in the CNS of rat were studied using the 2-deoxyglucose technique. Cerebral glucose utilization was determined for 53 brain regions at peak and descending blood ethanol concentrations averaging 14, 26 and 66 mM. Decreased glucose utilization was the predominant finding and was observed in 20% of the regions evaluated, with median raphe, vestibular nucleus, cerebellar vermis, and various structures associated with the auditory system showing the greatest reductions. The only structures that showed increased glucose utilization were the dentate region of the hippocampus and the superior olive, and this was only apparent at a blood ethanol concentration of 14 mM.

A comparison of calcium antagonists and diazepam in reducing ethanol withdrawal tremors

The calcium antagonists nimodipine and dantrolene were compared with diazepam in an animal model of tolerance and physical dependence upon ethanol. Nimodipine and dantrolene were both effective in suppressing withdrawal tremors but diazepam was clearly superior to both agents. These results suggest that the ethanol with-drawal syndrome is only partially mediated by increased calcium flux.

Cerebral 2-deoxyglucose uptake in rats during ethanol withdrawal and postwithdrawal.

The overt ethanol withdrawal syndrome is associated with a generalized increase in cerebral uptake of 2-deoxyglucose. Relatively high elevations of 2-deoxyglucose were observed in many structures associated with motor function, the mamillary body-anterior thalamus-cingulate cortex pathway, many thalamic nuclei, and the raphe. Overtly withdrawing rats had higher levels of 2-deoxyglucose than postwithdrawing animals that had been abstinent for 1-5 weeks in 96% of the gray areas evaluated. Postwithdrawal was associated with increased amounts of 2-deoxyglucose in comparison to controls in 80% of the gray areas evaluated. Postwithdrawal and control rats did not differ in some areas involved with motor function and some limbic structures, such as the mamillary body-anterior thalamus-cingulate cortex pathway. It is concluded that the ethanol-withdrawal syndrome results in alterations in cerebral physiology, some of which persist for at least 5 weeks postwithdrawal.

Studies of neurotransmitter interactions after acute and chronic ethanol administration

Evidence is accumulating suggesting that ethanol has a biphasic effect on several neurotransmitters in the brain and that interactions between two or more transmitters may contribute to the behavioral response obtained after ethanol administration. In the nigrostriatal complex where the most data have been derived, dopaminergic activity responds in a biphasic manner to ethanol treatment. At low doses, dopaminergic activity is elevated, while at high doses, activity is reduced. After chronic ethanol treatment, pre- and postsynaptic dopaminergic activity is hypoactive. Pharmacological data have suggested the possible involvement of acetylcholine (ACh) and gamma-aminobutyric acid (GABA) in the actions of ethanol on the striatal dopaminergic system. In support of this postulate, striatal high-affinity choline uptake, an index of ACh release, is elevated after high doses of ethanol and after ethanol withdrawal. GABA turnover exhibits a biphasic response to ethanol treatment. At low doses of ethanol, GABA turnover is reduced, while at high doses, turnover is unaffected. These latter effects correlate with known interrelationships of these transmitters in the nigrostriatal complex. The data suggest that an action of ethanol on one transmitter may influence the response of another transmitter to ethanol. To further address the interrelationship of transmitters, a high-performance liquid chromatographic method has been developed to study the activity of several transmitters simultaneously. This approach promises to shed more light on this important area.