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Recent advances in the understanding of the neurobiological basis of alcohol dependence suggest that the endocannabinoid system may play a key role in the reinforcing effects of ethanol. In the present study, disruption of CB1 receptors in mice generated on a CD1 background decreased both ethanol consumption and preference. This decreased ethanol self-administration was associated with increased sensitivity to the acute intoxicating effects of ethanol. Mutant mice were more sensitive to the hypothermic and sedative/hypnotic effects of acute ethanol administration (1.5-4.0 g/kg), although plasma ethanol concentrations did not differ from those of controls. Moreover, wild-type mice exhibited normal locomotor activation caused by 1.0-2.5 g/kg injection of ethanol, whereas mutant mice displayed sedation in response to the injection of the same ethanol doses. The severity of alcohol withdrawal-induced convulsions was also increased in CB1(-/-) mice. Our results suggest that CB1 receptors participate in the regulation of ethanol drinking and demonstrate that their disruption lead to increased ethanol sensitivity and withdrawal severity.

The effects of prenatal exposure to some drugs of abuse, such as nicotine, on breathing function have been clearly established. However, the case of alcohol (ethanol), the most widely consume drug of abuse, remains unknown. Prenatal ethanol consumption in humans may lead to fetal alcohol syndrome and although the effect of chronic prenatal ethanol exposure (CPEE) on cognitive function is frequently studied, nothing is known about CPEE's effects on breathing as compared with other drugs of abuse. The role of nicotine for example, in human neonatal pathology, such as sudden infant death syndrome, is acknowledged today, whereas the full scope of CPEE's role is only recently emerging. Here, we review preclinical investigations on the effects of CPEE on breathing in different animal models, including possible mechanisms of adaptation to CPEE. These recent preclinical studies shed new light on a widely used drug of abuse and should facilitate the understanding of the danger posed by alcohol consumption during pregnancy.

AbstractBackgroundMultiple ethanol binge drinking‐like exposures during adolescence in the rat induce neuroinflammation, loss of neurogenesis, and cognitive deficits in adulthood. Interestingly, the first ethanol binge drinking‐like exposure during adolescence also induces short‐ term impairments in cognition and synaptic plasticity in the hippocampus though the cellular mechanisms of these effects are unclear. Here, we sought to determine which of the cellular effects of ethanol might play a role in the disturbances in cognition and synaptic plasticity observed in the adolescent male rat after two binge‐like ethanol exposures.MethodsUsing immunochemistry, we measured neurogenesis, neuronal loss, astrogliosis, neuroinflammation, and synaptogenesis in the hippocampus of adolescent rats 48 h after two binge‐like ethanol exposures (3 g/kg, i.p., 9 h apart). We used flow cytometry to analyze activated microglia and identify the TLR4‐expressing cell types.ResultsWe detected increased hippocampal doublecortin immunoreactivity in the subgranular zone (SGZ) of the dentate gyrus (DG), astrogliosis in the SGZ, and a reduced number of mature neurons in the DG and in CA3, suggesting compensatory neurogenesis. Synaptic density decreased in the stratum oriens of CA1 revealing structural plasticity. There was no change in microglial TLR4 expression or in the number of activated microglia, suggesting a lack of neuroinflammatory processes, although neuronal TLR4 was decreased in CA1 and DG.ConclusionsOur findings demonstrate that the cognitive deficits associated with hippocampal synaptic plasticity alterations that we previously characterized 48 h after the first binge‐like ethanol exposures are associated with hippocampal structural plasticity, astrogliosis, and decreased neuronal TLR4 expression, but not with microglia reactivity.

The glutamatergic system plays a central role in both the acute and chronic effects of ethanol. Among all the glutamate receptors the ionotropic NMDA receptors are crucial because of their role in synaptic plasticity. A large body of evidences suggests that short-term and long-term effects of ethanol may change synaptic plasticity via an alteration of the expression of the GluN2B subunit, one constitutive element of the NMDA receptor. The present review is focusing on the role of the GluN2B subunit after ethanol exposure during early life (in utero and adolescence) and also at adulthood. The roles of other NMDA subunits are also discussed in the context of the increasing evidence that the ratio of the different subunits, such as GluN2A-to-GluN2B, seems to better reflect the effects of ethanol and to explain how ethanol exposure can have short lasting and long lasting effects on synaptic plasticity, cognitive processes and some of the ethanol-related behaviors.

Perinatal exposure to drugs of abuse, including alcohol (ethanol), is known to impinge the development of respiratory function. However, most studies described the short-term effects of these exposures, focusing mostly on the early postnatal life. After exposure to ethanol during gestation and lactation we have previously shown that 3-4 week-old rat exhibit chronic hypoventilation and an altered response to hypoxia at the end of ethanol exposure. However, whether these deficits are reversible following ethanol withdrawal remained unknown. Here, we investigated through whole-body plethysmography the respiratory activity of 2 months-old rats exposed to ethanol from gestation to weaning followed by one month of ethanol withdrawal. After ethanol withdrawal, rats persistently exhibited a significant reduction in respiratory frequency without change in tidal volume associated to a lower arterial blood oxygen content. In addition, the response to hypoxia in these rats was reduced whereas the response to hypercapnia remained unaltered. In conclusion perinatal exposure to ethanol in rats, unlike exposure to cocaine, morphine or nicotine, is characterized by selective alterations of basal respiratory activity and chemosensitivity that persist long after withdrawal.

Alcohol (ethanol) disturbs cognitive functions including learning and memory in humans, non-human primates, and laboratory animals such as rodents. As studied in animals, cellular mechanisms for learning and memory include bidirectional synaptic plasticity, long-term potentiation (LTP), and long-term depression (LTD), primarily in the hippocampus. Most of the research in the field of alcohol has analyzed the effects of ethanol on LTP; however, with recent advances in the understanding of the physiological role of LTD in learning and memory, some authors have examined the effects of ethanol exposure on this particular signal. In the present review, I will focus on hippocampal LTD recorded in rodents and the effects of fetal alcohol exposure on this signal. A synthesis of the findings indicates that prenatal ethanol exposure disturbs LTD concurrently with LTP in offspring and that both glutamatergic and γ-aminobutyric acid (GABA) neurotransmissions are altered and contribute to LTD disturbances. Although the ultimate mode of action of ethanol on these two transmitter systems is not yet clear, novel suggestions have recently appeared in the literature.

AbstractEthanol consumption impairs learning and memory through disturbances of NMDA‐type glutamate receptor‐dependent synaptic plasticity (long‐term depression [LTD] and long‐term potentiation [LTP]) in the hippocampus. Recently, we demonstrated that two ethanol binge‐like episodes in young adult rats selectively blocked NMDA‐LTD in hippocampal slices, increased NMDA receptor sensitivity to a GluN2B subunit antagonist, and induced cognitive deficits. Here, using knockout adult mice, we show that a stress‐responsive transcription factor of the heat shock factor family, HSF2, which is involved in the perturbation of brain development induced by ethanol, participates in these processes. In the absence of ethanol, hsf2−/− mice show a selective loss of LTD in the hippocampus, which is associated with an increased sensitivity of NMDA‐field excitatory postsynaptic potentials (fEPSPs) to a GluN2B antagonist, compared with wild‐type (WT) mice. These results suggest that HSF2 is required for proper glutamatergic synaptic transmission and LTD plasticity. After 1 month of chronic ethanol consumption in a two‐bottle choice paradigm, WT mice showed an increase in hippocampal synaptic transmission, an enhanced sensitivity to GluN2B antagonist, and a blockade of LTD. In contrast, such modulation of synaptic transmission and plasticity were absent in hsf2−/− mice. We conclude that HSF2 is an important mediator of both glutamatergic neurotransmission and synaptic plasticity in basal conditions and also mediates ethanol‐induced neuroadaptations of the hippocampus network after chronic ethanol intake.