Biphasic action of ethanol

The alcohol facilitation effect on memory: a dose-response study

Sixteen normal male subjects participated in four sessions where they studied a set of pictures followed by either placebo, 0.025, 0.50, or 1.0 ml/kg alcohol. Later, when sober, recognition memory was tested. These doses resulted in peak blood alcohol concentrations (BAC) of 0.00, 0.018, 0.034, and 0.067 g/100 ml, respectively. The 1.0 and 0.50 ml/kg doses significantly improved memory for pictures studied before drinking. Alcohol appears to enhance memory directly rather than indirectly via a reduction in interference. It is suggested that a particular phase of the rising blood alcohol curve (0.02-0.03 g/100 ml) facilitates trace consolidation. The facilitating and possibly excitatory effects of alcohol may be important for understanding the rewarding aspects of drinking.

The excitatory component of ethanol in mice: a chronic study

The effects of chronic administration of initially depressant, ineffective and excitatory doses of ethanol on the locomotor activity of mice was studied. The results showed that (1) an excitatory effect of ethanol is observed after tolerance develops to its depressant action; (2) the effect induced by an initially excitatory dose of ethanol became more pronounced with chronic exposure to the drug; and (3) tolerance to the excitatory effect was not reached after 60 days of ethanol treatment.

Biochemical evidence for an interaction of ethanol and stress: preliminary studies

Studies were carried out to examine the interaction of stress and ethanol. Ethanol (0.5 g/kg)-treated, stressed (electric foot shocks) rats exhibited less marked elevations in plasma levels of nonesterified fatty acids and of corticosterone compared to saline-treated stressed subjects. Stress alone markedly elevated these two parameters in plasma. Ethanol treatment alone also resulted in small elevations in both parameters. Results provide support for a significant interaction of ethanol and stress, and might provide some basis for the purported stress-relieving effect of low doses of ethanol.

Biphasic action of ethanol on single units of the dorsal hippocampus and the relationship to the cortical EEG

The effects of four doses of ethanol (100, 200, 400, 800 mg/kg) administered IV, on the spontaneous firing rate of single units in the dorsal hippocampal regin of the rat were studied. At the lower doses, a mixture of excitatory and inhibitory effects occurring in that order was seen, reflecting a biphasic action of ethanol at the level of the single neuron. As the dose increased, the excitation disappeared and successively greater degrees of response inhibition prevailed. The pattern of the fronto-cortical EEG changed from predominantly low amplitude fast activity with a few episodes of high amplitude slow activity at low doses, to more sustained episodes of slow activity at high doses. The time-response curve showed that the peak of maximum inhibition seen at the highest dose occurred with a longer latency than the peak of maximum excitation seen at the lower doses. Finally, the changes in unit firing appeared to follow four general patterns and to be correlated with the mode of fronto-cortical EEG activity.

Mood effects of alcohol

Doses of 0.41, 0.63, and 0.85 g alcohol/kg body weight were administered using a double-blind Latin square design to subjects who made mood ratings at seven points in time during 3h subsequent to administration. The subjects felt more euphoric and extraverted and less tense at mainly the highest dose levels. Lower dose levels tended to induce more negative feelings. Frequent consumers of alcohol derived greater affective benefit than rare drinkers. Intercorrelations between ratings of subjective intoxication and mood variables indicated that the meaning of the variable "subjective intoxication" was different for the three dose levels and for different points in time.

Antagonism of ethanol's central stimulation by catecholamine receptor agonists

The effect of ethanol (2 g/kg) on brain catecholamine neurons in the rat as well as its interaction with catecholamine receptor agonists was studied utilizing single unit recording techniques. Identified dopamine (DA) neurons of the zona compacta, substantia nigra as well as noradrenaline (NA) neurons of the locus coeruleus showed no alterations in firing rate at ethanol administration. Also the function of their presynaptic DA and NA receptors, respectively, appeared normal judging from the unaltered inhibitory response to systemically or microiontophoretically applied receptor agonists, apomorphine and clonidine, respectively, when applied in small doses. In contrast, the catecholamine releasing agent amphetamine caused inhibition of firing of the central catecholamine neurons in the same anesthetized preparation. The rate of tryosine hydroxylation in vivo in central DA and NA neurons measured as the amount of Dopa accumulated in various brain regions following inhibition of aromatic l-amino acid decarboxylase by NSD 1015, 150 md/kg i.p., was significantly increased by ethanol in anesthetized rats. Consequently, the present data do not support the hypothesis derived largely from behavioural evidence that ethanol causes inactivation of central DA and NA neurons. The antagonism by catecholamine receptor agonists, apomorphine and clonidine of ethanol's behaviourally stimulant action may thus be of unspecific character. The results indicate that alterations in tyrosine hydroxylase activity, when measured as Dopa formation after decarboxylase inhibition, can occur without concomitantly altered impulse activity in central DA or NA neurons. At present the action of ethanol on brain DA and NA neurons remains unclear and necessitates further studies.

Retrograde enhancement of human memory with alcohol

In two experiments with normal male subjects, the ingestion of alcohol (1 ml/kg) immediately after learning significantly improved subsequent remembering. By comparison, marijuana (15 mg) had no significant post-acquisition effect. Facilitation of visual and verbal memory with alcohol under these conditions has implications for the interference and consolidation views of memory.

Auditory evoked transient and sustained potentials in the human EEG: II. Effects of small doses of ethanol

The effect of small doses of ethanol (0.4 g/kg) on auditory evoked transient and sustained potentials was studied. Tones of 1-second duration were presented in trains of four stimuli (interstimulus interval = 1 second; intertrain interval = 1 minute). The electroencephalogram was recorded from derivation Cz-Al. Ethanol depressed the transient responses both at the first stimulus of the train and during repeated stimuli. The sustained potentials elicited by the first stimuli of the train were not affected by ethanol, whereas the sustained potentials elicited by repeated stimuli were larger in amplitude under the influence of ethanol than during control experiments. It is suggested that the decrease of the transient responses under the influence of ethanol is mainly due to depression of the reticular formation, whereas the increase of sustained potentials reflects ethanol-induced release of intracortical inhibition.

Reduction of swimming time in mice through interaction of infrasound and alcohol

The effects of noise, alcohol, and the combination of the two were studied on muscular fatigue in several mouse strains to investigate a possible interaction between the two stresses. Muscular fatigue was measured by latency to submersion during a forced-swimming test. Animals were exposed to acoustic stimuli of fixed frequency and intensity for 2h preceding the test. Ethanol was administered orally from 30 min to 3h 30 min prior to testing. Alcohol doses and sound intensities were subliminal when administered separately. While no significant interaction occurred between alcohol and audible sound, the interaction between alcohol and infrasound was highly significant indicating that their joint effects are more than merely additive. Blood alcohol measurements indicate that these interactive effects are prolonged for more than 2h after elimination of alcohol from the blood. Effects are similar in genetically deaf and hearing mice, implicating involvement of nonauditory pathways.

Noradrenergic processes involved in the locomotor effects of ethanol

Male albino Wistar rats were depleted of forebrain noradrenaline by intracerebral injection of 4 microgram of 6-hydroxydopamine into the noradrenaline bundles in the mesencephalon. The locomotor response was examined in response to intraperitoneal injection of ethanol. The locomotor stimulation by 0.1 g/kg ethanol was not altered by the lesion, whereas the sedation found in response to 1 g/kg in controls failed to occur in the lesioned rats and instead a stimulation was seen.