Our studies indicate that, in the presence of particular isoforms of adenylyl cyclase (i.e., type 7 AC), moderately intoxicating concentrations of ethanol will significantly potentiate transmitter-mediated activation of the cAMP signaling cascade. Activation of this signaling cascade may have important implications for the mechanisms by which ethanol produces intoxication, and/or for the mechanisms of neuroadaptation leading to tolerance to, and physical dependence on, ethanol. We initiated a series of studies to investigate the phosphorylation of AC7 by PKC, the role of this phosphorylation in modulating the sensitivity of AC7 to activation by Gsalpha, and the PKC isotype(s) involved in the phosphorylation of AC7. The T7 epitope-tagged AC7 expressed in Sf9 and HEK293 cells was found to be phosphorylated in vitro by the catalytic subunit of PKC. Treatment of AC7-transfected HEK293 cells with phorbol dibutyrate (PDBu) or ethanol increased the phosphorylation of AC7 and its responsiveness to Gsalpha. In human erythroleukemia (HEL) cells, which endogeneously express AC7, ethanol and PDBu increased AC activity stimulated by PGE(1). The potentiation by both PDBu and ethanol was found to be sensitive to the PKC delta-selective inhibitor, rottlerin. The potentiation of AC activity by ethanol in HEL cells was also selectively attenuated by the RACK inhibitory peptide specific for PKC delta, and by expression of the dominant negative, catalytically inactive, form of PKC delta. These data demonstrate that AC7 can be phosphorylated by PKC, leading to an increase in functional activity, and ethanol can potentiate AC7 activity through a PKC delta-mediated phosphorylation of AC7.

Adenylyl Cyclases↗

PubMedDate not supplied

Peptide--neurotransmitter interactions influencing ethanol tolerance.

Chronic exposure of mice to ethanol leads to the development of functional tolerance to the hypothermic and sedative effects of this drug. Treatment of the animals with the mammalian antidiuretic hormone, arginine vasopressin, results in a prolonged duration of such tolerance, in comparison to animals exposed to ethanol but not to the hormone. Another neurohypophyseal hormone, oxytocin, at an equimolar dose, is ineffective in maintaining tolerance. The centrally mediated effects of arginine vasopressin on memory processes may be related to the hormone-induced prolongation of ethanol tolerance.

Animals↗

PubMedDate not supplied

Adaptive changes in the dopamine system produced by chronic ethanol feeding.

The consumption of ethanol by mice resulted in an altered sensitivity of the brain dopamine systems to perturbations produced by agonists and antagonists. The results indicate that ethanol feeding and withdrawal produces a state in which the normal coupling between dopamine receptors and the effectors for these receptors is significantly altered.

Adenylyl Cyclases↗

PubMedDate not supplied

Acute tolerance in inbred and selected lines of mice.

Mice of the C57Bl and C3H strains regained their righting reflex at higher brain ethanol levels than those at which they had lost their righting reflex, indicating that these animals developed acute tolerance. DBA mice did not develop acute tolerance. DBA mice "slept" significantly longer than C57Bl mice, but all mice lost their righting reflex at similar brain ethanol levels. Mice of SS and LS lines also showed no evidence for developing acute tolerance but differed significantly in brain ethanol levels upon loss of righting reflex. Both acute tolerance development and initial brain sensitivity to ethanol seem to determine duration of ethanol "sleep time" in mice.

Animals↗

PubMedDate not supplied

Characterization of brain acetaldehyde oxidizing systems in the mouse.

C57BL mice were treated (75 or 100 mg/kg) with pargyline or Lilly 51641 90 min prior to sacrifice. Liver and brain subcellular fractionation revealed that pretreatment with these drugs resulted in a significant inhibition of aldehyde dehydrogenase (ALDH) in liver cytosol and mitochondria, while brain ALDH in these same fractions was unaffected. Administration of pargyline or Lilly 51641 prior to ethanol treatment (3.0 g/kg) resulted in a significant elevation of blood acetaldehyde. Significant increases in brain acetaldehyde concentrations were not observed until blood acetaldehyde levels surpassed 200 nmol/ml. When mice were injected with ethanol (3.0 g/kg) and acetaldehyde (200 mg/kg), a similar relationship between blood and brain acetaldehyde concentrations was observed. Data presented in the present study indicate that there are very efficient enzymatic mechanisms responsible for acetaldehyde oxidation in brain and that at blood acetaldehyde concentratins normally occurring after ethanol ingestion, brain acetaldehyde levels would be extremely low.

Acetaldehyde↗

PubMedDate not supplied

Binding characteristics of 3H-flunitrazepam and CL-218,872 in cerebellum and cortex of C57B1 mice made tolerant to and dependent on phenobarbital or ethanol.

The influence of chronic phenobarbital (PB) or chronic ethanol administration on binding characteristics of 3H-flunitrazepam (3H-FLU) in cerebellum and cortex of C57Bl mice was examined. Chronic PB treatment for six days decreased the number of binding sites (Bmax) for 3H-FLU, whereas no change in the affinity (KD) was found. Further kinetic analysis revealed that the overall decrease in Bmax was due to a reduced number of high affinity (Type 1) benzodiazepine (BDZ) binding sites in the cerebellum, but to a decreased number of low affinity (Type 2) BDZ binding sites in the cortex. Furthermore, a marked reduction in the pentobarbital-produced enhancement of 3H-FLU binding was observed in the cerebellum of the PB-treated animals. Following chronic ethanol administration for seven days, no change in the Bmax or in the KD could be demonstrated. However, in chronically ethanol-treated mice, the pentobarbital-induced stimulation of 3H-FLU binding was reduced in the cerebellum of mice 24 hours after discontinuation of the ethanol treatment. The significance of the present findings for the development of tolerance to and dependence on barbiturates and ethanol is discussed.

Alcoholism↗

PubMedDate not supplied

Basal firing rate of rat locus coeruleus neurons affects sensitivity to ethanol.

Intracellular recordings were made from spontaneously active rat locus coeruleus (LC) neurons in a totally submerged brain slice preparation. Bath application of ethanol (ETOH) (1-60 mM) inhibited the spontaneous firing of LC neurons. These ETOH concentrations are equal to or below ETOH concentrations found in the brain during mild to moderate intoxication. The basal frequency of spontaneous firing of LC neurons ranged from 0.4-7 Hz. For 9 LC neurons which showed complete block of firing by ETOH, the latency to block was found to be directly related to the logarithm of the firing rate (correlation coefficient 0.94). This relationship was not secondary to a relationship between membrane potential and latency to block since for the same 9 neurons, membrane potential and latency to block were not significantly correlated. We conclude that the basal firing rate of a neuron can affect its sensitivity to the inhibitory effects of ETOH.

Animals↗

PubMedDate not supplied

Characteristics of receptors and enzymes in brains of human alcoholics.

Acute and chronic ethanol administration to animals has been shown to produce changes in the turnover of numerous neurotransmitters, as well as to change the characteristics of certain neurotransmitter receptors. In the present study, brains obtained from human alcoholics and matched control subjects were examined for similar changes. In frontal cortex, the affinity of opiate receptors for dihydromorphine was significantly reduced in brains of alcoholics. Judging from animal studies, this change may reflect alterations in opiate receptor-effector coupling processes. No changes were observed in muscarinic cholinergic or beta-adrenergic receptors in humans, in contrast to animals, possibly because of the protracted abstention from alcohol among the alcoholic patients prior to death. Similarly, no changes in the activities of choline acetyltransferase, tyrosine hydroxylase or MAO-B were observed in brains of alcoholics as compared to the control population. Our studies suggest that many of the alterations witnessed during alcohol intoxication and withdrawal in animals may be more subtle in humans, or may be reversible with abstinence.

Alcoholism↗

PubMedDate not supplied

Ethanol does not affect serotonin receptor binding in rodent brain.

The effects of ethanol on serotonin (5-hydroxytryptamine, 5-HT) receptor binding in rat and mouse brain were determined under in vitro conditions and in mouse brain following seven days of ethanol ingestion. 5-HT1A receptor characteristics were measured utilizing the agonist [3H]8-hydroxy-2-(di-n-propylamino)tetralin ([ 3H]DPAT), and 5HT2 receptor-binding studies utilized the antagonist [3H]ketanserin. At the highest concentration of ethanol tested in vitro (680 mM), there was only 25% inhibition of [3H]DPAT binding in rat and mouse brain and 14% inhibition of [3H]ketanserin binding in rat brain. Effects of an anesthetic concentration of ethanol (100 mM) on agonist binding in the presence and absence of the guanine nucleotide GTP were also evaluated in vitro in mouse brain. In no case did ethanol (100 mM) significantly affect 5-HT1A or 5-HT2 receptor-binding characteristics. When 5-HT receptor characteristics were measured after mice consumed ethanol for seven days, there was no change in either 5-HT1A or 5-HT2 receptor-binding properties in any of the brain areas examined.

8-Hydroxy-2-(di-n-propylamino)tetralin↗