Developmental changes in alcohol pharmacokinetics in rats

Exploratory studies of ethanol drinking in the white-tufted marmoset (Callithrix jacchus)

The white-tufted marmoset is a small, nonhuman primate that is rapidly gaining popularity as a model organism, especially for neuroscience research. To date, little work in the alcohol research field has utilized the marmoset. As a step toward establishing the marmoset as a research model for alcohol experimentation, a series of exploratory studies were undertaken to characterize ethanol drinking behavior. A voluntary drinking paradigm was established whereby the common marmoset would consume pharmacologically relevant amounts of ethanol. To facilitate ethanol consumption, ethanol was mixed with a marshmallow flavored solution (hereafter called marshmallow juice) to mask the presumed adverse taste of ethanol. Using marshmallow juice flavored solutions, marmosets readily consumed ethanol up to 1 g/kg during 10 min binge-like drinking sessions or up to 5 g/kg during ∼4 h drinking sessions. Consumption of 1.0-1.5 g/kg during a 30 min session resulted in blood ethanol concentrations of 49-73 mg/dl, which are predicted to be pharmacologically relevant. In animals that were stably consuming ethanol in marshmallow juice, gradually reducing the concentration of the marshmallow juice flavoring resulted in markedly reduced ethanol consumption. Lastly, when offered a choice between ethanol in marshmallow juice and marshmallow juice alone, marmosets displayed a very strong preference for the marshmallow juice solution without ethanol. From these studies, it is concluded that marmosets will voluntarily consume ethanol if the taste is masked with a sweet solution such as marshmallow juice. These studies represent the first report of alcohol consumption and preference in the white-tufted marmoset.

Choline Supplementation Alters Hippocampal Cytokine Levels in Adolescence and Adulthood in an Animal Model of Fetal Alcohol Spectrum Disorders

Alcohol (ethanol) exposure during pregnancy can adversely affect development, with long-lasting consequences that include neuroimmune, cognitive, and behavioral dysfunction. Alcohol-induced alterations in cytokine levels in the hippocampus may contribute to abnormal cognitive and behavioral outcomes in individuals with fetal alcohol spectrum disorders (FASD). Nutritional intervention with the essential nutrient choline can improve hippocampal-dependent behavioral impairments and may also influence neuroimmune function. Thus, we examined the effects of choline supplementation on hippocampal cytokine levels in adolescent and adult rats exposed to alcohol early in development. From postnatal day (PD) 4-9 (third trimester-equivalent), Sprague-Dawley rat pups received ethanol (5.25 g/kg/day) or sham intubations and were treated with choline chloride (100 mg/kg/day) or saline from PD 10-30; hippocampi were collected at PD 35 or PD 60. Age-specific ethanol-induced increases in interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and keratinocyte chemoattractant/human growth-regulated oncogene (KC/GRO) were identified in adulthood, but not adolescence, whereas persistent ethanol-induced increases of interleukin-6 (IL-6) levels were present at both ages. Interestingly, choline supplementation reduced age-related changes in interleukin-1 beta (IL-1β) and interleukin-5 (IL-5) as well as mitigating the long-lasting increase in IFN-γ in ethanol-exposed adults. Moreover, choline influenced inflammatory tone by modulating ratios of pro- to -anti-inflammatory cytokines. These results suggest that ethanol-induced changes in hippocampal cytokine levels are more evident during adulthood than adolescence, and that choline can mitigate some effects of ethanol exposure on long-lasting inflammatory tone.

Moderate ethanol exposure during early ontogeny of the rat alters respiratory plasticity, ultrasonic distress vocalizations, increases brain catalase activity, and acetaldehyde-mediated ethanol intake

Early ontogeny of the rat (late gestation and postnatal first week) is a sensitive period to ethanol’s positive reinforcing effects and its detrimental effects on respiratory plasticity. Recent studies show that acetaldehyde, the first ethanol metabolite, plays a key role in the modulation of ethanol motivational effects. Ethanol brain metabolization into acetaldehyde via the catalase system appears critical in modulating ethanol positive reinforcing consequences. Catalase system activity peak levels occur early in the ontogeny. Yet, the role of ethanol-derived acetaldehyde during the late gestational period on respiration response, ultrasonic vocalizations (USVs), and ethanol intake during the first week of the rat remains poorly explored. In the present study, pregnant rats were given a subcutaneous injection of an acetaldehyde-sequestering agent (D-penicillamine, 50 mg/kg) or saline (0.9% NaCl), 30 min prior to an intragastric administration of ethanol (2.0 g/kg) or water (vehicle) on gestational days 17–20. Respiration rates (breaths/min) and apneic episodes in a whole-body plethysmograph were registered on postnatal days (PDs) 2 and 4, while simultaneously pups received milk or ethanol infusions for 40-min in an artificial lactation test. Each intake test was followed by a 5-min long USVs emission record. On PD 8, immediately after pups completed a 15-min ethanol intake test, brain samples were collected and kept frozen for catalase activity determination. Results indicated that a moderate experience with ethanol during the late gestational period disrupted breathing plasticity, increased ethanol intake, as well brain catalase activity. Animals postnatally exposed to ethanol increased their ethanol intake and exerted differential affective reactions on USVs and apneic episodes depending on whether the experience with ethanol occur prenatal or postnatally. Under the present experimental conditions, we failed to observe, a clear role of acetaldehyde mediating ethanol’s effects on respiratory plasticity or affective states, nevertheless gestational acetaldehyde was of crucial importance in determining subsequent ethanol intake affinity. As a whole, results emphasize the importance of considering the participation of acetaldehyde in fetal programming processes derived from a brief moderate ethanol experience early in development, which in turn, argues against “safe or harmless” ethanol levels of exposure.

Choline Supplementation Modifies the Effects of Developmental Alcohol Exposure on Immune Responses in Adult Rats

Prenatal alcohol exposure can disrupt the development of numerous systems, including the immune system. Indeed, alterations in cytokine levels may contribute to the neuropathological, behavioral, and cognitive problems, and other adverse outcomes observed in individuals with fetal alcohol spectrum disorders. Importantly, supplementation with the essential nutrient choline can improve performance in hippocampal-dependent behaviors; thus, the present study examined the effects of choline on plasma and hippocampal cytokines in adult rats exposed to ethanol in early development. From postnatal day (PD) 4–9 (third trimester equivalent), pups received ethanol (5.25 g/kg/day) or Sham intubations. Subjects were treated with choline chloride (100 mg/kg/day) or saline from PD10–30. On PD60, plasma and hippocampal tissue was collected before and after an immune challenge (lipopolysaccharide (LPS); 50 ug/kg). Prior to the immune challenge, ethanol-exposed subjects showed an overall increase in hippocampal pro-inflammatory cytokines, an effect mitigated by choline supplementation. In contrast, in the plasma, choline reduced LPS-related increases in pro-inflammatory markers, particularly in ethanol-exposed subjects. Thus, early choline supplementation may modify both brain and peripheral inflammation. These results suggest that early choline can mitigate some long-term effects of ethanol exposure on hippocampal inflammation, which may contribute to improved hippocampal function, and could also influence peripheral immune responses that may impact overall health.

Rat Model of Late Gestational Alcohol Exposure Produces Similar Life-Long Changes in Thalamic Nucleus Reuniens Following Moderate- Versus High-Dose Insult

AIMS

Recent studies have recognized that thalamic nucleus reuniens (Re) undergoes substantial neuron loss following alcohol exposure (AE) during the brain growth spurt (BGS). As all previous studies have utilized high-dose AE paradigms, we tested whether moderate-dose AE is capable of damaging Re to a similar degree as high-dose AE.

METHODS

We used a rat model of third-trimester binge AE (relative to human pregnancy) to administer ethanol to rat pups at either a high (5.25 g/kg/day) or moderate (3.00 g/kg/day) dose during the BGS (postnatal days [PD] 4-9) via intragastric intubation. In adulthood (i.e. PD72), we quantified the volume of Re as well as the total number of neurons and non-neuronal cells in the nucleus (which were further divided into microglia versus 'other' non-neurons), using unbiased stereological estimation of cells identified with immunofluorescent markers (i.e. nuclear label Hoechst, neuron-specific protein NeuN, and microglia-specific protein Iba1). Data were analyzed both between-treatment and correlated with peak blood alcohol concentration (BAC).

RESULTS AND CONCLUSIONS

We observed significant neuronal and non-neuronal cell loss in both the high-dose and moderate-dose AE groups (relative to both procedural control and typically-developing control groups), which mediated reductions in Re volume. Outcomes did not correlate with peak BAC, further supporting that Re is vulnerable to AE-induced neurodegeneration at lower doses than previously suspected. Given the role that Re has in coordinating prefrontal cortex and hippocampus, the current study highlights the role that thalamic damage may play in the range of behavioral alterations observed in Fetal Alcohol Spectrum Disorders.

Executive functioning-specific behavioral impairments in a rat model of human third trimester binge drinking implicate prefrontal-thalamo-hippocampal circuitry in Fetal Alcohol Spectrum Disorders

Individuals diagnosed with Fetal Alcohol Spectrum Disorders (FASD) often display behavioral impairments in executive functioning (EF). Specifically, the domains of working memory, inhibition, and set shifting are frequently impacted by prenatal alcohol exposure. Coordination between prefrontal cortex and hippocampus appear to be essential for these domains of executive functioning. The current study uses a rodent model of human third-trimester binge drinking to identify the extent of persistent executive functioning deficits following developmental alcohol by using a behavioral battery of hippocampus- and prefrontal cortex-dependent behavioral assays in adulthood. Alcohol added to milk formula was administered to Long Evans rat pups on postnatal days 4-9 (5.25 g/kg/day of ethanol; intragastric intubation), a period when rodent brain development undergoes comparable processes to human third-trimester neurodevelopment. Procedural control animals underwent sham intubation, without administration of any liquids (i.e., alcohol, milk solution). In adulthood, male rats were run on a battery of behavioral assays: novel object recognition, object-in-place associative memory, spontaneous alternation, and behavioral flexibility tasks. Alcohol-exposed rats demonstrated behavioral impairment in object-in-place preference and performed worse when the rule was switched on a plus maze task. All rats showed similar levels of novel object recognition, spontaneous alternation, discrimination learning, and reversal learning, suggesting alcohol-induced behavioral alterations are selective to executive functioning domains of spatial working memory and set-shifting in this widely-utilized rodent model. These specific behavioral alterations support the hypothesis that behavioral impairments in EF following prenatal alcohol exposure are caused by distributed damage to the prefrontal-thalamo-hippocampal circuit consisting of the medial prefrontal cortex, thalamic nucleus reuniens, and CA1 of hippocampus.

The offspring of alcohol-exposed sires exhibit heightened ethanol intake and behavioral alterations in the elevated plus maze

Research suggests that addictive traits are indeed heritable, but very few preclinical studies have explored transgenerational effects of paternal alcohol exposure. The present study addressed this gap in knowledge. We explored whether offspring of ethanol-exposed sires would be more likely to accept ethanol than descendants of water-exposed and control sires. We also investigated whether the second generation of ethanol-exposed descendants would accept ethanol more than controls and were more or less likely to experience anxiety-like behavior in behavioral assessments. We exposed male rats to repeated binge doses of alcohol (4 g/kg/day across 8 days), water, or left them untreated and mated them with untreated females. We then bred the offspring of these rats to test transgenerational effects of paternal alcohol exposure. We tested 14-day-old offspring from the first and second filial generation for their acceptance of ethanol and water, and measured anxiety-like behavior in 38-day-old, second-generation offspring using an elevated plus maze. The results indicate that offspring of ethanol-exposed sires increase ethanol acceptance in the first generation compared to untreated controls, whereas in the second-generation increased ethanol acceptance vs. these controls is seen in descendants of both ethanol- and vehicle-treated sires. At adolescence, the second generation of rats derived from alcohol-exposed sires exhibited significantly more time spent in the open arms and significantly more arm entries than any other group. The present study suggests that parental ethanol exposure is associated with lingering effects in the infant and adolescent offspring. The second filial generation was also found to be affected, albeit similarly by grandparental ethanol exposure or by the stress of the vehicle administration.

Changes in Representation of Thalamic Projection Neurons within Prefrontal-Thalamic-Hippocampal Circuitry in a Rat Model of Third Trimester Binge Drinking

Alcohol exposure (AE) during the third trimester of pregnancy-a period known as the brain growth spurt (BGS)-could result in a diagnosis of a fetal alcohol spectrum disorder (FASD), a hallmark of which is impaired executive functioning (EF). Coordinated activity between prefrontal cortex and hippocampus is necessary for EF and thalamic nucleus reuniens (Re), which is required for prefrontal-hippocampal coordination, is damaged following high-dose AE during the BGS. The current experiment utilized high-dose AE (5.25 g/kg/day) during the BGS (i.e., postnatal days 4-9) of Long-Evans rat pups. AE reduces the number of neurons in Re into adulthood and selectively alters the proportion of Re neurons that simultaneously innervate both medial prefrontal cortex (mPFC) and ventral hippocampus (vHPC). The AE-induced change unique to Re→(mPFC + vHPC) projection neurons (neuron populations that innervate either mPFC or vHPC individually were unchanged) is not mediated by reduction in neuron number. These data are the first to examine mPFC-Re-HPC circuit connectivity in a rodent model of FASD, and suggest that both short-term AE-induced neuron loss and long-term changes in thalamic connectivity may be two distinct (but synergistic) mechanisms by which developmental AE can alter mPFC-Re-vHPC circuitry and impair EF throughout the lifespan.

Moderate Adolescent Ethanol Vapor Exposure and Acute Stress in Adulthood: Sex-Dependent Effects on Social Behavior and Ethanol Intake in Sprague-Dawley Rats

Adolescent alcohol use can lead to numerous consequences, including altered stress reactivity and higher risk for later anxiety and alcohol use disorders. Many studies have examined the consequences of heavy ethanol exposure in adolescence, but far less is understood about lower levels of intoxication. The present study examined moderate adolescent ethanol exposure as a possible factor in increasing stress reactivity in adulthood, measured through general and social anxiety-like behaviors, as well voluntary ethanol intake. Male and female Sprague-Dawley rats underwent an adolescent chronic intermittent ethanol (aCIE) vapor exposure during early adolescence, reaching moderate blood ethanol concentrations. Animals then underwent two days of forced swim stress in adulthood. We found that ethanol-exposed males consumed more ethanol than their air counterparts and an interesting stress and ethanol exposure interaction in males. There were no significant effects on voluntary drinking in females. However, the social interaction test revealed increased play-fighting behavior in ethanol-exposed females and reduced social preference in females after two days of stress exposure. Overall, this work provides evidence for sex-specific, long-term effects of moderate aCIE and susceptibility to acute stress in adulthood.

Single-day Postnatal Alcohol Exposure Induces Apoptotic Cell Death and Causes long-term Neuron Loss in Rodent Thalamic Nucleus Reuniens

Fetal alcohol spectrum disorders (FASD) constitute a prevalent, yet preventable, developmental disorder worldwide. While a wealth of research demonstrates that altered function of hippocampus (HPC) and prefrontal cortex may underlie behavioral impairments in FASD, only one published paper to date has examined the impact of developmental alcohol exposure (AE) on the region responsible for coordinated prefrontal-hippocampal activity: thalamic nucleus reuniens (Re). In the current study, we used a rodent model of human third trimester AE to examine both the acute and lasting impact of a single-day AE on Re. We administered 5.25 g/kg of ethanol to male and female Long Evans rat pups on postnatal day (PD) 7. We used unbiased stereological estimation to evaluate cell death or cell loss at three time points: 12 h after alcohol administration; 4 days after alcohol administration (i.e., PD11); in adulthood (i.e.,PD 72). AE on PD7 increased apoptotic cell death in Re on PD7, and caused short-term cell loss on PD11. This relationship between short-term cell death versus cell number suggests that alcohol-related cell loss is driven by induction of apoptosis. In adulthood, alcohol-exposed animals displayed permanent cell loss (mediating volume loss in the Re), which included a reduction in neuron number (relative to procedural controls). Both procedural controls and alcohol exposed animals displayed a deficit in non-neuronal cell number relative to typically-developing controls, suggesting that Re cell populations may be vulnerable to early life stress as well as AE in an insult- and cell type-dependent manner.

Nucleus reuniens of the midline thalamus of a rat is specifically damaged after early postnatal alcohol exposure

Individuals diagnosed with fetal alcohol spectrum disorders often show behavioral impairments in executive functioning. Mechanistic studies have implicated coordination between the prefrontal cortex and the hippocampus (through thalamic nucleus reuniens) as essential for such executive functions. This study is the first to report the long-term neuroanatomical alterations to the ventral midline thalamus after alcohol exposure on postnatal days 4-9 (a rodent model of binge drinking during the third-trimester of human pregnancy). Alcohol added to a milk formula was administered to female Long-Evans rat pups on postnatal days 4-9 (5.25 g/kg/day of ethanol, intragastric intubation). Control animals were intubated without the administration of liquid. In adulthood, brains were immunohistochemically labeled for a neuronal marker (NeuN) conjugated with Cy3 fluorophore and stained with Hoechst33342 to visualize nuclei. Total non-neuronal cell number (NeuN/Hoechst) and neuron number (NeuN/Hoechst), and total volume were estimated using unbiased stereology in two neighboring midline thalamic nuclei: reuniens and rhomboid. Estimates were analyzed using linear mixed modeling to account for animal and litter as clustering variables. A 21% reduction in the total neuron number (resulting in altered neuron-to-non-neuron ratio) and an 18% reduction in total volume were found exclusively in thalamic nucleus reuniens in rats exposed to ethanol. Non-neuronal cell number was not changed in reuniens. No ethanol-induced changes on any measures were observed in rhomboid nucleus. These specific neuroanatomical alterations provide a necessary foundation for further examination of circuit-level alterations that occur in fetal alcohol spectrum disorder.

Fetal Alcohol Programming of Subsequent Alcohol Affinity: A Review Based on Preclinical, Clinical and Epidemiological Studies

The anatomo-physiological disruptions inherent to different categories of the Fetal Alcohol Spectrum Disorder do not encompass all the negative consequences derived from intrauterine ethanol (EtOH) exposure. Preclinical, clinical and epidemiological studies show that prenatal EtOH exposure also results in early programming of alcohol affinity. This affinity has been addressed through the examination of how EtOH prenatally exposed organisms recognize and prefer the drug’s chemosensory cues and their predisposition to exhibit heightened voluntary EtOH intake during infancy and adolescence. In altricial species these processes are determined by the interaction of at least three factors during stages equivalent to the 2nd and 3rd human gestational trimester: (i) fetal processing of the drug’s olfactory and gustatory attributes present in the prenatal milieu; (ii) EtOH’s recruitment of central reinforcing effects that also imply progressive sensitization to the drug’s motivational properties; and (iii) an associative learning process involving the prior two factors. This Pavlovian learning phenomenon is dependent upon the recruitment of the opioid system and studies also indicate a significant role of EtOH’s principal metabolite (acetaldehyde, ACD) which is rapidly generated in the brain via the catalase system. The central and rapid accumulation of this metabolite represents a major factor involved in the process of fetal alcohol programming. According to recent investigations, it appears that ACD exerts early positive reinforcing consequences and antianxiety effects (negative reinforcement). Finally, this review also acknowledges human clinical and epidemiological studies indicating that moderate and binge-like drinking episodes during gestation result in neonatal recognition of EtOH’s chemosensory properties coupled with a preference towards these cues. As a whole, the studies under discussion emphasize the notion that even subteratogenic EtOH exposure during fetal life seizes early functional sensory and learning capabilities that pathologically shape subsequent physiological and behavioral reactivity towards the drug.

Sex and Individual Differences in Alcohol Intake Are Associated with Differences in Ketamine Self-Administration Behaviors and Nucleus Accumbens Dendritic Spine Density

Clinical and preclinical studies have shown that ketamine, an NMDA receptor antagonist, has promising therapeutic value for the treatment of alcohol use disorder (AUD). However, the maintenance of remission will ultimately require repeated infusions of ketamine, which may lead to abuse potential and may hinder its therapeutic benefits. It is therefore crucial to assess the effects of repeated treatments with ketamine on alcohol intake. Accordingly, this study aimed to examine in both sexes how individual differences in alcohol intake alter ketamine self-administration and how ketamine self-administration will alter subsequent alcohol-drinking behaviors. Male and female rats intermittently drank alcohol or water for 10 weeks and were divided into high- or low-alcohol intake groups prior to ketamine self-administration. Rats self-administered ketamine under fixed and progressive ratio schedules of reinforcement from week 4 to 7, and the incubation of ketamine craving was examined from week 8 to 10. To investigate structural plasticity in a brain region involved in reward, nucleus accumbens dendritic spine morphology was examined. Our results show that high alcohol intake in male rats attenuated ketamine self-administration, whereas in female rats high alcohol intake enhanced motivation to self-administer ketamine. Ketamine reduced alcohol intake in high-alcohol male rats but increased it in low-alcohol female rats. Incubation of ketamine craving developed in all groups except low-alcohol females. Three weeks of abstinence from ketamine was associated with increased mushroom spines in all groups except the high-alcohol male group. Overall, these data suggest that ketamine as a treatment for AUD may benefit male subjects, but not female subjects, and warrants further investigation before use as a therapeutic agent.

Altered motor development following late gestational alcohol and cannabinoid exposure in rats

Cannabis is the most commonly used illicit drug among pregnant women, and rates are likely to increase given recent legalization. In addition, half of pregnant women who report consuming cannabis also report drinking alcohol. However, little is known about the consequences of prenatal cannabis alone or in combination with alcohol, particularly with cannabis products that are continually increasing in potency of the primary psychoactive constituent in cannabis, Δ9-tetrahydrocannabinol (THC). The current study investigated the effects of early exposure to cannabinoids during the brain growth spurt on early physical and motor development alone (Experiment 1) or in combination with alcohol (Experiment 2). In Experiment 1, Sprague-Dawley rat pups were exposed to a cannabinoid receptor agonist (CP-55,940 [CP]; 0.1, 0.25, 0.4 mg/kg/day), the drug vehicle, or a saline control from postnatal days (PD) 4-9. In Experiment 2, rat pups were exposed to CP (0.4 mg/kg/day) or the vehicle, and were additionally intubated with alcohol (11.9% v/v; 5.25 g/kg/day) or received a sham intubation. Subjects in both experiments were tested on a motor development task (PD 12-20) and a motor coordination task during adolescence (PD 30-32). Both developmental cannabinoid and alcohol exposure separately decreased body growth throughout development, and combined exposure exacerbated these effects, although only alcohol exposure induced long-term body weight reductions. Developmental cannabinoid exposure advanced early motor development, whereas alcohol exposure delayed development, and subjects given combined exposure did not differ from controls on some measures. Alcohol exposure impaired motor coordination later in life. In contrast, cannabinoid exposure, by itself, did not significantly affect long-term motor coordination, but did exacerbate alcohol-related impairments in motor coordination among females. These results suggest that cannabinoid exposure may not only alter development by itself, but may exacerbate alcohol's teratogenic effects in specific behavioral domains. These findings have important implications not only for individuals affected by prenatal exposure, but also for establishing public policy for women regarding cannabis use during pregnancy.

Recurrent binge ethanol is associated with significant loss of dentate gyrus granule neurons in female rats despite concomitant increase in neurogenesis

Binge drinking is becoming increasingly common among American women and girls. We have previously shown significant cell loss, downregulation of neurotrophins and microgliosis in female rats after a single 4-day ethanol exposure. To determine whether recurrent binge exposure would produce similar effects, we administered ethanol (5 g/kg) or iso-caloric control diet once-weekly for 11 weeks to adult female rats. As we have previously shown exercise neuroprotection against binge-induced damage, half the rats were given access to exercise wheels. Blood ethanol concentration (BEC) did not differ between sedentary and exercised groups, nor did it change across time. Using stereology, we quantified the number and/or size of neurons in the medial prefrontal cortex (mPFC) and hippocampal dentate gyrus (DG), as well as the number and activation state of microglia. Binged sedentary rats had significant cell loss in the dentate gyrus, but exercise eliminated this effect. Compared to sedentary controls, sedentary binged rats and all exercised rats showed increased neurogenesis in the DG. Number and nuclear volume of neurons in the mPFC were not changed. In the hippocampus and mPFC, the number of microglia with morphology indicative of partial activation was increased by recurrent binge ethanol and decreased by exercise. In summary, we show significant binge-induced loss of DG granule neurons despite increased neurogenesis, suggesting an unsuccessful compensatory response. Although exercise eliminated cell loss, our results indicate that infrequent, but recurrent exposure to clinically relevant BEC is neurotoxic.

Lack of sexual dimorphism on the inhibitory effect of alcohol on muscle protein synthesis in rats under basal conditions and after anabolic stimulation

Previous studies indicate women have a higher blood alcohol (i.e., ethanol) and acetaldehyde concentration after consuming an equivalent amount of alcohol, and that women are more susceptible to the long-term negative health effects of alcohol. However, there is a paucity of data pertaining to whether there is a sexual dimorphic response in skeletal muscle to alcohol. Adult male and female Sprague-Dawley rats were used and the primary endpoint was in vivo determined muscle (gastrocnemius) protein synthesis (MPS). The initial study indicated MPS did not differ in female rats during proestrus, estrus, metestrus, or diestrus; hence, subsequent studies used female rats irrespective of estrus cycle phase. There was no difference in MPS between male and female rats under basal fasted conditions, and the time- and dose-responsiveness of both groups to the inhibitory effect of acute alcohol did not differ. The ability of alcohol to suppress MPS was comparable in male and female rats pretreated with alcohol dehydrogenase inhibitor 4-methylpyrazol. Chronic alcohol feeding for 6 weeks decreased MPS in male but not in female rats; however, MPS was reduced in both sexes at 14 weeks. Finally, oral gavage of leucine increased MPS similarly in male and female rats and chronic alcohol feeding for 14 weeks prevented the anabolic effect in both sexes. These data suggest normal fluctuations in ovarian hormones do not significantly alter MPS in female rats, and that there is no sexual dimorphic response to the effects of acute alcohol intoxication on MPS. While chronic alcohol consumption appeared to decrease MPS at an early time point in male compared to female rats, there was no sex difference in the suppressive effect of alcohol at a later time point. Overall, these data do not support the prevailing belief that females are more susceptible than males to alcohol's catabolic effect on MPS.

Ethanol Sensitization during Adolescence or Adulthood Induces Different Patterns of Ethanol Consumption without Affecting Ethanol Metabolism

In previous study, we demonstrated that ethanol preexposure may increase ethanol consumption in both adolescent and adult mice, in a two-bottle choice model. We now questioned if ethanol exposure during adolescence results in changes of consumption pattern using a three-bottle choice procedure, considering drinking-in-the-dark and alcohol deprivation effect as strategies for ethanol consumption escalation. We also analyzed aldehyde dehydrogenase (ALDH) activity as a measurement of ethanol metabolism. Adolescent and adult Swiss mice were treated with saline (SAL) or 2.0 g/kg ethanol (EtOH) during 15 days (groups: Adolescent-SAL, Adolescent-EtOH, Adult-SAL and Adult-EtOH). Five days after the last injection, mice were exposed to the three-bottle choice protocol using sucrose fading procedure (4% + sucrose vs. 8%–15% ethanol + sucrose vs. water + sucrose) for 2 h during the dark phase. Sucrose was faded out from 8% to 0%. The protocol was composed of a 6-week acquisition period, followed by four withdrawals and reexposures. Both adolescent and adult mice exhibited ethanol behavioral sensitization, although the magnitude of sensitization in adolescents was lower than in adults. Adolescent-EtOH displayed an escalation of 4% ethanol consumption during acquisition that was not observed in Adult-EtOH. Moreover, Adult-EtOH consumed less 4% ethanol throughout all the experiment and less 15% ethanol in the last reexposure period than Adolescent-EtOH. ALDH activity varied with age, in which older mice showed higher ALDH than younger ones. Ethanol pretreatment or the pattern of consumption did not have influence on ALDH activity. Our data suggest that ethanol pretreatment during adolescence but not adulthood may influence the pattern of ethanol consumption toward an escalation in ethanol consumption at low dose, without exerting an impact on ALDH activity.

Adolescent Alcohol Exposure Persistently Impacts Adult Neurobiology and Behavior

Adolescence is a developmental period when physical and cognitive abilities are optimized, when social skills are consolidated, and when sexuality, adolescent behaviors, and frontal cortical functions mature to adult levels. Adolescents also have unique responses to alcohol compared with adults, being less sensitive to ethanol sedative-motor responses that most likely contribute to binge drinking and blackouts. Population studies find that an early age of drinking onset correlates with increased lifetime risks for the development of alcohol dependence, violence, and injuries. Brain synapses, myelination, and neural circuits mature in adolescence to adult levels in parallel with increased reflection on the consequence of actions and reduced impulsivity and thrill seeking. Alcohol binge drinking could alter human development, but variations in genetics, peer groups, family structure, early life experiences, and the emergence of psychopathology in humans confound studies. As adolescence is common to mammalian species, preclinical models of binge drinking provide insight into the direct impact of alcohol on adolescent development. This review relates human findings to basic science studies, particularly the preclinical studies of the Neurobiology of Adolescent Drinking in Adulthood (NADIA) Consortium. These studies focus on persistent adult changes in neurobiology and behavior following adolescent intermittent ethanol (AIE), a model of underage drinking. NADIA studies and others find that AIE results in the following: increases in adult alcohol drinking, disinhibition, and social anxiety; altered adult synapses, cognition, and sleep; reduced adult neurogenesis, cholinergic, and serotonergic neurons; and increased neuroimmune gene expression and epigenetic modifiers of gene expression. Many of these effects are specific to adolescents and not found in parallel adult studies. AIE can cause a persistence of adolescent-like synaptic physiology, behavior, and sensitivity to alcohol into adulthood. Together, these findings support the hypothesis that adolescent binge drinking leads to long-lasting changes in the adult brain that increase risks of adult psychopathology, particularly for alcohol dependence.

Neonatal experiences with ethanol intoxication modify respiratory and thermoregulatory plasticity and affect subsequent ethanol intake in rats

Different studies have focused on the deleterious consequences of binge-like or chronic exposure to ethanol during the brain growth spurt period (third human gestational trimester) that in the rat corresponds to postnatal days (PDs) 3-10. The present study analyzed behavioral and physiological disruptions caused by relatively brief binge-like exposures (PDs 3, 5, and 7) with an ethanol dose lower (3.0 g/kg) than those frequently employed to examine teratological effects during this stage in development. At PD 9, pups were exposed to ethanol doses ranging between .0-3.0 g/kg and tested in terms of breathing patterns and thermoregulation. At PDs 11 and 12, ethanol intake was examined. The main findings were as follows: i) pre-exposure to the drug resulted in brief depressions in breathing frequencies and an exacerbated predisposition toward apneic episodes; ii) these effects were not dependent upon thermoregulatory alterations; iii) early ethanol treatment increased initial consumption of the drug which also caused a marked hypothermia that appeared to regulate a subsequent decrement in ethanol consumption; and iv) ethanol exposure retarded overall body growth and even one exposure to the drug (PD 9) was sufficient to reduce brain weights although there were no indications of microcephaly. In conjunction with studies performed during the late gestational period in the rat, the results indicate that relatively brief binge-like episodes during a critical window of brain vulnerability disrupts the respiratory network and exacerbates initial acceptance of the drug. In addition, ethanol treatments were not found to induce tolerance relative to respiratory and thermal disruptions.

Apoptotic cell death and temporal expression of apoptotic proteins Bcl-2 and Bax in the hippocampus, following binge ethanol in the neonatal rat model

BACKGROUND

Binge-like ethanol (EtOH) exposure during the early rat neonatal period results in acute cell loss in specific brain regions, but such acute cell death has not been well established in the hippocampus. Binge alcohol exposure can also result in protein expression changes in the cerebellum that could alter cell fate, but this has not been reported for the hippocampal subregions. This study investigates acute apoptotic cell death in hippocampal regions CA1, CA3, and dentate gyrus (DG) following a binge EtOH exposure on postnatal day (PN) 6, PN8, or PN6 + 8 and the alteration in pro- and anti-apoptotic proteins following a single EtOH binge on PN6.

METHODS

Apoptotic cell death was quantified 12 hours after EtOH binge exposure using the optical fractionator method. Western blot analysis determined expression of pro-apoptotic Bax and anti-apoptotic Bcl-2, 12, 24, and 48 hours after binge EtOH exposure on PN6. The Bcl-2:Bax ratio was used as a measure of vulnerability to apoptosis.

RESULTS

Acute apoptosis increased significantly 12 hours following PN6 or 8 EtOH exposure in CA1, CA3, and DG, but the magnitude of apoptotic cell death was significantly greater in CA1 than in CA3 and DG, which did not differ. Significant cell death was not detected when a PN8 EtOH exposure was preceded by exposure on PN6. Binge EtOH exposure on PN6 resulted in a significant increase in expression of Bcl-2 and the Bcl-2:Bax ratio in the CA1/DG region at 24 hours after EtOH exposure on PN6. The Bcl-2:Bax ratio in the CA3 region was not altered.

CONCLUSIONS

This study shows that repeated binge exposure does not have a cumulative effect on the magnitude of acute apoptotic cell death. This finding may be explained in part by changes in the Bcl-2:Bax ratio after a single binge EtOH exposure.

Importance of genetics in fetal alcohol effects: null mutation of the nNOS gene worsens alcohol-induced cerebellar neuronal losses and behavioral deficits

The cerebellum is a major target of alcohol-induced damage in the developing brain. However, the cerebella of some children are much more seriously affected than others by prenatal alcohol exposure. As a consequence of in utero alcohol exposure, some children have substantial reductions in cerebellar volume and corresponding neurodevelopmental problems, including microencephaly, ataxia, and balance deficits, while other children who were exposed to similar alcohol quantities are spared. One factor that likely plays a key role in determining the impact of alcohol on the fetal cerebellum is genetics. However, no specific gene variant has yet been identified that worsens cerebellar function as a consequence of developmental alcohol exposure. Previous studies have revealed that mice carrying a homozygous mutation of the gene for neuronal nitric oxide synthase (nNOS-/- mice) have more severe acute alcohol-induced neuronal losses from the cerebellum than wild type mice. Therefore, the goals of this study were to determine whether alcohol induces more severe cerebellum-based behavioral deficits in nNOS-/- mice than in wild type mice and to determine whether these worsened behavior deficits are associated with worsened cerebellar neuronal losses. nNOS-/- mice and their wild type controls received alcohol (0.0, 2.2, or 4.4mg/g) daily over postnatal days 4-9. In adulthood, the mice underwent behavioral testing, followed by neuronal quantification. Alcohol caused dose-related deficits in rotarod and balance beam performance in both nNOS-/- and wild type mice. However, the alcohol-induced behavioral deficits were substantially worse in the nNOS-/- mice than in wild type. Likewise, alcohol exposure led to losses of Purkinje cells and cerebellar granule cells in mice of both genotypes, but the cell losses were more severe in the nNOS-/- mice than in wild type. Behavioral performances were correlated with neuronal number in the nNOS-/- mice, but not in wild type. Thus, homozygous mutation of the nNOS gene increases vulnerability to alcohol-induced cerebellar dysfunction and neuronal loss. nNOS is the first gene identified whose mutation worsens alcohol-induced cerebellar behavioral deficits.

Dihydromyricetin prevents fetal alcohol exposure-induced behavioral and physiological deficits: the roles of GABAA receptors in adolescence

Fetal alcohol exposure (FAE) can lead to a variety of behavioral and physiological disturbances later in life. Understanding how alcohol (ethanol, EtOH) affects fetal brain development is essential to guide the development of better therapeutics for FAE. One of EtOH's many pharmacological targets is the γ-aminobutyric acid type A receptor (GABAAR), which plays a prominent role in early brain development. Acute EtOH potentiates inhibitory currents carried by certain GABAAR subtypes, whereas chronic EtOH leads to persistent alterations in GABAAR subunit composition, localization and function. We recently introduced a flavonoid compound, dihydromyricetin (DHM), which selectively antagonizes EtOH's intoxicating effects in vivo and in vitro at enhancing GABAAR function as a candidate for alcohol abuse pharmacotherapy. Here, we studied the effect of FAE on physiology, behavior and GABAAR function of early adolescent rats and tested the utility of DHM as a preventative treatment for FAE-induced disturbances. Gavage administration of EtOH (1.5, 2.5, or 5.0 g/kg) to rat dams on day 5, 8, 10, 12, and 15 of pregnancy dose-dependently reduced female/male offspring ratios (largely through decreased numbers of female offspring) and offspring body weights. FAE (2.5 g/kg) rats tested on postnatal days (P) 25-32 also exhibited increased anxiety and reduced pentylenetetrazol (PTZ)-induced seizure threshold. Patch-clamp recordings from dentate gyrus granule cells (DGCs) in hippocampal slices from FAE (2.5 g/kg) rats at P25-35 revealed reduced sensitivity of GABAergic miniature inhibitory postsynaptic currents (mIPSCs) and tonic current (Itonic) to potentiation by zolpidem (0.3 μM). Interestingly, potentiation of mIPSCs by gaboxadol increased, while potentiation of Itonic decreased in DGCs from FAE rats. Co-administration of EtOH (1.5 or 2.5 g/kg) with DHM (1.0 mg/kg) in pregnant dams prevented all of the behavioral, physiological, and pharmacological alterations observed in FAE offspring. DHM administration alone in pregnant rats had no adverse effect on litter size, progeny weight, anxiety level, PTZ seizure threshold, or DGC GABAAR function. Our results indicate that FAE induces long-lasting alterations in physiology, behavior, and hippocampal GABAAR function and that these deficits are prevented by DHM co-treatment of EtOH-exposed dams. The absence of adverse side effects and the ability of DHM to prevent FAE consequences suggest that DHM is an attractive candidate for development as a treatment for prevention of fetal alcohol spectrum disorders.

Associations between sleep disturbance and alcohol drinking: A large-scale epidemiological study of adolescents in Japan

In this study, we attempted to clarify the associations between various sleep disturbance symptoms and the frequency and amount of alcohol use among Japanese adolescents. This study was designed as a cross-sectional sampling survey. A self-administered questionnaire survey was administered to students enrolled in randomly selected junior and senior high schools throughout Japan. A total of 99,416 adolescents responded, and 98,867 questionnaires were subjected to analysis. The prevalence rates of sleep disturbance in the 30 days preceding the day of the survey were as follows: subjectively insufficient sleep (SIS) (boys: 37.6%, girls: 38.7%); short sleep duration (SSD) with less than 6 h of sleep (boys: 28.0%, girls: 33.0%); difficulty initiating sleep (DIS) (boys: 12.5%, girls: 14.1%); difficulty maintaining sleep (DMS) (boys: 10.1%, girls: 10.9%); and early morning awakening (EMA) (boys: 5.1%, girls: 5.0%). Adolescents reporting one or more symptoms of DIS, DMS, and EMA were classified as having insomnia, and its prevalence was 21.5%. The prevalence of each symptom of sleep disturbance increased significantly with the number of days on which alcohol was consumed in the previous 30 days and the amount of alcohol consumed per drinking session (p < 0.01). Multiple logistic regression analyses showed that the adjusted odds ratio (AOR) for each symptom of sleep disturbance, except SIS and EMA, tended to increase with the number of days on which alcohol was consumed and the amount of alcohol consumed per drinking session. The prevalence of sleep disturbance is particularly high among adolescents drinking alcohol. The risk of having each symptom of sleep disturbance, except SIS and EMA, increases with the number of days on which alcohol was consumed and the amount of alcohol consumed per drinking session. These findings reconfirm the need to eliminate underage drinking to ensure good sleep among adolescents.

Cholecalciferol attenuates perseverative behavior associated with developmental alcohol exposure in rats in a dose-dependent manner

Alcohol is a known teratogen that is estimated to affect 2-5% of the births in the U.S. Prenatal alcohol exposure can produce physical features such as facial dysmorphology, physiological alterations such as cell loss in the central nervous system (CNS), and behavioral changes that include hyperactivity, cognitive deficits, and motor dysfunction. The range of effects associated with prenatal alcohol exposure is referred to as fetal alcohol spectrum disorders (FASD). Despite preventative measures, some women continue to drink while pregnant. Therefore, identifying interventions that reduce the severity of FASD is critical. This study investigated one such potential intervention, vitamin D3, a nutrient that exerts neuroprotective properties. The present study determined whether cholecalciferol, a common vitamin D3 nutritional supplement, could serve as a means of mitigating alcohol-related learning deficits. Using a rat model of FASD, cholecalciferol was given before, during, and after 3rd trimester equivalent alcohol exposure. Three weeks after cholecalciferol treatment, subjects were tested on a serial spatial discrimination reversal learning task. Animals exposed to ethanol committed significantly more errors compared to controls. Cholecalciferol treatment reduced perseverative behavior that is associated with developmental alcohol exposure in a dose-dependent manner. These data have important implications for the treatment of FASD and suggest that cholecalciferol may reduce some aspects of FASD. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Acetaldehyde involvement in ethanol's postabsortive effects during early ontogeny

Clinical and biomedical studies sustains the notion that early ontogeny is a vulnerable window to the impact of alcohol. Experiences with the drug during these stages increase latter disposition to prefer, use or abuse ethanol. This period of enhanced sensitivity to ethanol is accompanied by a high rate of activity in the central catalase system, which metabolizes ethanol in the brain. Acetaldehyde (ACD), the first oxidation product of ethanol, has been found to share many neurobehavioral effects with the drug. Cumulative evidence supports this notion in models employing adults. Nevertheless very few studies have been conducted to analyze the role of ACD in ethanol postabsorptive effects, in newborns or infant rats. In this work we review recent experimental literature that syndicates ACD as a mediator agent of reinforcing aspects of ethanol, during early ontogenetic stages. We also show a meta-analytical correlational approach that proposes how differences in the activity of brain catalase across ontogeny, could be modulating patterns of ethanol consumption.

The role of acetaldehyde in ethanol reinforcement assessed by Pavlovian conditioning in newborn rats

RATIONALE

Animal studies indicate that central acetaldehyde, dependent on catalase metabolism of ethanol (EtOH), modulates ethanol reinforcement. Brain catalase activity and acetaldehyde (ACD) production are significantly higher in rat pups compare d with adults. Interestingly, infant rats show high EtOH affinity for alcohol consumption and are particularly sensitive to the drug's reinforcing effects.

OBJECTIVES

We tested whether central ACD is necessary and sufficient to induce appetitive conditioning in newborn rats through the artificial nipple technique.

METHODS

Vehicle, EtOH (100 mg%), and acetaldehyde (0.35 μmol) were administered into the cisterna magna (1 μl). Half of the animals also received a central administration of 75 μg (experiment 1) or 40 μg of D-penicillamine (experiment 2). Afterwards, pups were exposed to an olfactory cue (conditioned stimulus). One hour later, neonates were tested with an artificial nipple in the presence of the conditioned cue. Nipple attachment duration, mean grasp duration, and number of nipple disengagements served as dependent variables.

RESULTS

Positive responses to the scented nipple occurred in neonates conditioned with EtOH or ACD (experiments 1 and 2). In experiment 1, there were indications that D-penicillamine weakened the reinforcing effects of EtOH and ACD. In experiment 2, D-penicillamine (40 μg) significantly inhibited appetitive conditioned responses dependent upon EtOH or ACD.

CONCLUSIONS

Appetitive conditioning was observed when employing either central EtOH or ACD as unconditioned stimuli. Central abduction of ACD inhibited conditioned appetitive responsiveness to the surrogate nipple. Central ACD is involved in the determination or modulation of EtOH's motivational properties during early stages in development.

Blood alcohol levels for American Indian mothers and newborns

Very little is known about the alcohol elimination rates of newborns who have had chronic alcohol exposure in utero. In these case reports, blood alcohol levels were taken immediately before delivery, at delivery, and postdelivery for 2 mothers who drank alcohol during their pregnancies and 3 single-birth newborns. Newborn A1 of Mother A had no physical characteristics of fetal alcohol syndrome (FAS). The initial blood alcohol level for this newborn was 38.4 mg/dL 129 minutes after birth, with a subsequent blood alcohol level of 5.5 mg/dL 304 minutes after delivery, resulting in an alcohol elimination rate of 11.3 mg/dL per hour. The blood alcohol level for Mother A was 87.4 mg/dL 66 minutes before delivery. Newborn A2 of mother A had FAS. Sixty minutes after delivery, the blood alcohol level for this newborn was 39.5 mg/dL, and the alcohol level of the mother was 42.1 mg/dL. Newborn B1 of mother B had FAS. At 67 minutes after birth, newborn B1 had a blood alcohol level of 246.5 mg/dL, which dropped to 178.7 mg/dL 302 minutes after birth, resulting in an alcohol elimination rate of 17.3 mg/dL per hour. This alcohol elimination rate is within the metabolism range (15-49 mg/dL per hour) of adults with alcoholism. The maternal blood alcohol level was 265.9 mg/dL 27 minutes before delivery. Blood alcohol levels drawn on both the mother and newborn at delivery and 2 or 3 hourly follow-up levels can provide evidence that fetal alcohol dehydrogenase activity is induced by chronic maternal alcohol use.

Ontogenetic differences in ethanol's motivational properties during infancy

Pairing a conditioned stimulus (CS) with ethanol generally produces aversion for that CS in adult rodents. However, infant rats (PD1-PD3) exposed to ethanol demonstrate appetitive reinforcement to ethanol (Nizhnikov, Varlinskaya, Petrov, & Spear, 2006; Petrov, Varlinskaya, & Spear, 2003). This sensitivity to the appetitive properties of ethanol during infancy may be transient, as during the second postnatal week rat pups tend to exhibit conditioned aversions to flavors paired with ethanol. The present study examined changes in the motivation properties of ethanol through ontogeny and the neurobiology underlying these changes. Rat pups were exposed to a taste conditioning procedure on PD4 or PD12. Rat pups were intraorally infused with 2.5% of their body weight of saccharin solution (0.1%) and immediately after injected intraperitoneolly (i.p.) with one of six doses of ethanol (0.0-2.0 g/kg). A day later pups were given saccharine infusions and percent body weight gain was used as an index of ethanol's reinforcing effects. PD4 pups expressed appetitive reinforcement to ethanol, as indicated by greater saccharin intake, as compared to control counterparts and to the older PD12 pups. Subsequent experiments revealed that PD4 pups were less sensitive to the aversive properties of the drug than PD12 pups. The older pups found high doses of ethanol aversive while PD4 rat pups did not condition aversions to this dose of ethanol after a single trial. A similar pattern of results was observed between the low doses of ethanol and the highest doses of a kappa opioid agonist. The PD12 animals did not condition to the kappa opioid agonist, while the younger rats expressed an appetitive response. These results illustrate an ontogenetic change in the motivational properties of ethanol, with sensitivity to its appetitive properties declining and responsiveness to the aversive properties increasing with age during early infancy.

Chronic tolerance to the locomotor stimulating effect of ethanol in preweanling rats as a function of social stress

During early stages of development rats are highly sensitive to the locomotor stimulating effect of relatively high ethanol doses, an effect strongly modulated by social stress. This ethanol effect can be modulated by pharmacological treatments that also can attenuate the development of ethanol-induced locomotor sensitization in mice. By the end of the preweanling period the mechanisms underlying sensitization induced by psychostimulants are functional. The aim of the present study was to analyze the locomotor response to ethanol in preweanling rats as a function of repeated exposure to the drug under two different social conditions. Subjects were treated with ethanol between postnatal days 15 and 18 after being isolated for four hours (Experiment 1a) or simply residing in their home-cage (Experiment 1b). After two days of withdrawal locomotor response to ethanol was assessed in both social conditions. In Experiment 2 naïve rats were tested in terms of ethanol-induced activation of the locomotor response in both social conditions. Results from the present study showed no evidence of locomotor sensitization in preweanling rats in any of the social conditions. Instead we observed behavioral tolerance to the stimulating effect of ethanol in animals trained in the home-cage condition, in which subjects trained with ethanol showed sedation in response to ethanol at testing. Overall these results contribute to the understanding of the sensitivity of rats to the acute and chronic locomotor response to ethanol in an ontogenetic period characterized by high sensitivity to ethanol.

Acute and long-term Purkinje cell loss following a single ethanol binge during the early third trimester equivalent in the rat

BACKGROUND

In the rat, binge-like ethanol (EtOH) exposure during the early neonatal period (a developmental period equivalent to the human third trimester) can result in a permanent deficit of cerebellar Purkinje cells (Pcells). However, the consequences of a moderate binge alcohol exposure on a single day during this postnatal period have not been established. This is an issue of importance as many pregnant women binge drink periodically at social drinking levels. This study aimed to identify both the acute and long-term effects of exposure to a single alcohol binge that achieved a mean peak blood EtOH concentration of approximately 250 mg/dl during early postnatal life using a rat model of fetal alcohol spectrum disorders.

METHODS

Acute apoptotic Pcell death 10 hours after a moderate dose binge EtOH exposure from postnatal days (PDs) 0 to 10 was assessed using active caspase-3 immunolabeling. Acute Pcell apoptosis was quantified in cerebellar vermal lobules I-X using the physical disector method. Long-term effects were assessed at PD 60 using stereological methods to determine total Pcell numbers in the vermis, lobule III, and lobule IX, following a moderate dose binge EtOH exposure at PDs 0, 2, or 4.

RESULTS

Acute apoptosis was induced by EtOH on PDs 1 to 8 in a time and lobular-dependent manner. For EtOH exposure on PD 2, significant long-term Pcell loss occurred in lobule III. EtOH exposure on PD 4 resulted in significant long-term Pcell loss throughout the entire vermis.

CONCLUSIONS

These results indicate that a single, early EtOH episode of moderate dose can create significant and permanent Pcell loss in the developing cerebellum.

Neonatal alcohol exposure and the hippocampus in developing male rats: effects on behaviorally induced CA1 c-Fos expression, CA1 pyramidal cell number, and contextual fear conditioning

Rats exposed to a high binge-like dose of alcohol over postnatal days (PD) 4-9 show reductions in CA1 pyramidal cells and impairments on behavioral tasks that depend on the hippocampus. We first examined hippocampal c-Fos expression as a marker of neuronal activity in normally developing rats following different phases of the context preexposure facilitation effect (CPFE) paradigm (Experiment 1). During the CPFE, preexposure to the training context facilitates contextual conditioning to an immediate shock given on a subsequent occasion. We then examined the relationship between CPFE impairment, hippocampal cell loss, and c-Fos expression in rats exposed to alcohol over PD 4-9 (Experiment 2). Normally developing (Experiment 1), sham-intubated control (SI), and PD 4-9 alcohol-exposed (4.00 g and 5.25 g/kg/d; Experiment 2) juvenile male rats were trained on the CPFE. The CPFE occurs over three phases separated by 24 h. Starting on PD 31, rats were preexposed to Context A or Context B for 5 min. After 24 h, all rats received an immediate 1.5-mA foot shock in Context A. Finally, rats were tested for contextual conditioning in Context A on PD 33. Normally developing and SI rats preexposed to Context A showed enhanced contextual fear compared with those preexposed to Context B (Experiment 1) or alcohol-exposed rats preexposed to Context A (Experiment 2). Rats were sacrificed 2 h following different phases of the CPFE and processed for c-Fos immunohistochemistry (Experiments 1 and 2) and CA1 pyramidal cell quantification (Experiment 2). In Experiment 1, c-Fos positive (c-Fos+) cells in the dentate gyrus (DG) were consistently high among rats preexposed to Context A (Pre), Context B (No Pre), or sacrificed directly from their home cage (Home) and did not differ across CPFE phases. CA3 and CA1 c-Fos+ cells were highest during preexposure and decreased across training phases, with Group No Pre showing greater numbers of c-Fos+ cells during training than Group Pre and Controls. In Experiment 2, SI rats had greater numbers of CA1 c-Fos+ cells compared with alcohol-exposed rats, differing significantly from rats exposed to the high alcohol dose (5.25 g) over PD 4-9. Experiment 2 also revealed a linear decline in CA1 pyramidal cells across treatment groups, again with rats from the high-alcohol dose group showing significantly fewer CA1 pyramidal cells compared with SI. Our results reveal that context novelty may be a significant contributor to differential hippocampal c-Fos expression following different phases of the CPFE. In addition, lower levels of c-Fos+ cells in alcohol-exposed rats following preexposure may be related to general reductions in the number of CA1 pyramidal cells in these rats. The significant CPFE impairments in rats exposed to the lower alcohol dose (4.00 g), who show a 15% reduction in CA1 pyramidal cells compared with SI rats, highlight the sensitivity of the CPFE to hippocampal insult.

The effects of a single memantine treatment on behavioral alterations associated with binge alcohol exposure in neonatal rats

BACKGROUND

The third trimester in human fetal development represents a critical time of brain maturation referred to as the "brain growth spurt". This period occurs in rats postnatally, and exposure to ethanol during this time can increase the risk of impairments on a variety of cognitive and motor tasks. It has been proposed that one potential mechanism for the teratogenic effects of ethanol is NMDA receptor-mediated excitotoxicity during periods of ethanol withdrawal. In neonatal rats, antagonism of NMDA receptors during ethanol withdrawal, with drugs such as MK-801 and eliprodil, has been shown to mitigate some of the behavioral deficits induced by developmental ethanol exposure. The current study examined whether memantine, an NMDA receptor antagonist and a drug used clinically in Alzheimer's patients, would attenuate impairments associated with binge ethanol exposure in neonatal rats.

METHODS

On postnatal day 6, rats were exposed to 6 g/kg ethanol via intubation with controls receiving an isocaloric maltose dextrin solution. Twenty-one hours following the ethanol binge, rats received intraperitoneal injections of memantine at 0, 10, 15, or 20 mg/kg. Ethanol's teratogenic effects were assessed using multiple behavioral tasks: open field activity, parallel bars and spatial discrimination reversal learning.

RESULTS

Ethanol-treated rats were overactive in the open field and were impaired on both reversal learning and motor performance. Administration of 15 or 20 mg/kg memantine during withdrawal significantly attenuated ethanol's adverse effects on motor coordination, but did not significantly alter activity levels or improve the spatial learning deficits associated with neonatal alcohol exposure.

CONCLUSION

These results indicate that a single memantine administration during ethanol withdrawal can mitigate motor impairments but not spatial learning impairments or overactivity observed following a binge ethanol exposure during development in the rat.

Alcohol-induced neuronal death in central extended amygdala and pyriform cortex during the postnatal period of the rat

Mothers who consume alcohol during pregnancy may cause a neurotoxic syndrome defined as fetal alcohol spectrum disorder (FASD) in their offspring. This disorder is characterized by reduction in brain size, cognitive deficits and emotional/social disturbances. These alterations are thought to be caused by an alcohol-induced increase in apoptosis during neurodevelopment. Little is known about neuroapoptosis in the central extended amygdala and the pyriform cortex, which are key structures in emotional/social behaviors. The goal of this study was to determine the vulnerability of neuroapoptotic alcohol effects in those areas. Rats were administered alcohol (2.5g/kg s.c. at 0 and 2h) or saline on postnatal day (PND) 7, 15 and 20. The Amino-cupric-silver technique was used to evaluate neurodegeneration and immunohistochemistry to detect activated caspases 3-8 and 9 at 2h, 4, 6, 8, 12 and 24h after drug administration. We measured blood alcohol levels each hour, from 2 to 8h post second administration of alcohol in each of the ages studied. Results showed alcohol induced apoptotic neurodegeneration in the central extended amygdala on PND 7 and 15, and pyriform cortex on PND 7, 15 and 20. These structures showed activation of caspase 3 and 9 but not of caspase 8 suggesting that alcohol-induced apoptosis could occur by the intrinsic pathway. The pharmacokinetic differences between ages did not associate with the neurodegeneration age dependence. In conclusion, these limbic areas are damaged by alcohol, and each one has their own window of vulnerability during the postnatal period. The possible implications in emotional/social features in FASD are discussed.

Chronic intermittent ethanol exposure in early adolescent and adult male rats: effects on tolerance, social behavior, and ethanol intake

BACKGROUND

Given the prevalence of alcohol use in adolescence, it is important to understand the consequences of chronic ethanol exposure during this critical period in development. The purpose of this study was to assess possible age-related differences in susceptibility to tolerance development to ethanol-induced sedation and withdrawal-related anxiety, as well as voluntary ethanol intake after chronic exposure to relatively high doses of ethanol during adolescence or adulthood.

METHODS

Juvenile/adolescent and adult male Sprague-Dawley rats were assigned to one of five 10-day exposure conditions: chronic ethanol (4 g/kg every 48 hours), chronic saline (equivalent volume every 24 hours), chronic saline/acutely challenged with ethanol (4 g/kg on day 10), nonmanipulated/acutely challenged with ethanol (4 g/kg on day 10), or nonmanipulated. For assessment of tolerance development, duration of the loss of righting reflex (LORR) and blood ethanol concentrations (BECs) upon regaining of righting reflex (RORR) were tested on the first and last ethanol exposure days in the chronic ethanol group, with both saline and nonmanipulated animals likewise challenged on the last exposure day. Withdrawal-induced anxiety was indexed in a social interaction test 24 hours after the last ethanol exposure, with ethanol-naïve chronic saline and nonmanipulated animals serving as controls. Voluntary intake was assessed 48 hours after the chronic exposure period in chronic ethanol, chronic saline and nonmanipulated animals using an 8-day 2 bottle choice, limited-access ethanol intake procedure.

RESULTS

In general, adolescent animals showed shorter durations of LORR and higher BECs upon RORR than adults on the first and last ethanol exposure days, regardless of chronic exposure condition. Adults, but not adolescents, developed chronic tolerance to the sedative effects of ethanol, tolerance that appeared to be metabolic in nature. Social deficits were observed after chronic ethanol in both adolescents and adults. Adolescents drank significantly more ethanol than adults on a gram per kilogram basis, with intake uninfluenced by prior ethanol exposure at both ages.

CONCLUSIONS

Adolescents and adults may differ in their ability and/or propensity to adapt to chronic ethanol exposure, with adults, but not adolescents, developing chronic metabolic tolerance. However, this chronic exposure regimen was sufficient to disrupt baseline levels of social behavior at both ages. Taken together, these results suggest that, despite the age-related differences in tolerance development, adolescents are as susceptible as adults to consequences of chronic ethanol exposure, particularly in terms of disruptions in social behavior. Whether these effects would last into adulthood remains to be determined.

Ethanol induces second-order aversive conditioning in adolescent and adult rats

Alcohol abuse and dependence are considered public health problems, with an etiological onset often occurring during late childhood and adolescence, and understanding age-related differences in ethanol sensitivity is important. Low to moderate ethanol doses (0.5 and 2.0 g/kg, intragastrically [i.g.]) induce single-trial, appetitive second-order place conditioning (SOC) in adolescent, but not adult, rats. Recent studies have demonstrated that adolescents may be less sensitive than adults to the aversive properties of ethanol, reflected by conditioned taste aversion. The present study assessed the aversive motivational effects of high-dose ethanol (3.0 and 3.25 g/kg, i.g., for adolescents and adults, respectively) using SOC. Experiment 1 revealed similar blood and brain ethanol levels in adolescent and adult rats given 3.0 and 3.25 g/kg ethanol, respectively. In Experiment 2, animals received ethanol or vehicle paired with intraoral pulses of sucrose (conditioned stimulus 1 [CS1]). After one, two, or three conditioning trials, the rats were presented with the CS1 while in a distinctive chamber (CS2). When tested for CS2 preference, ethanol-treated animals exhibited reduced preference for the CS2 compared with controls. This result, indicative of ethanol-mediated aversive place conditioning, was similar for adolescents and adults; for females and males; and after one, two, or three training trials. In conjunction with previous results, the present study showed that, in adolescent rats subjected to SOC, ethanol's hedonic effects vary from appetitive to aversive as the ethanol dose increases. Adolescent and adult animals appear to perceive the postingestive effects of high-dose ethanol as similarly aversive when assessed by SOC.

Dopamine receptors modulate ethanol's locomotor-activating effects in preweanling rats

Near the end of the second postnatal week motor activity is increased soon after ethanol administration (2.5 g/kg) while sedation-like effects prevail when blood ethanol levels reach peak values. This time course coincides with biphasic reinforcement (appetitive and aversive) effects of ethanol determined at the same age. The present experiments tested the hypothesis that ethanol-induced activity during early development in the rat depends on the dopamine system, which is functional in modulating motor activity early in ontogeny. Experiments 1a and 1b tested ethanol-induced activity (0 or 2.5 g/kg) after a D1-like (SCH23390; 0, .015, .030, or .060 mg/kg) or a D2-like (sulpiride; 0, 5, 10, or 20 mg/kg) receptor antagonist, respectively. Ethanol-induced stimulation was suppressed by SCH23390 or sulpiride. The dopaminergic antagonists had no effect on blood ethanol concentration (Experiments 2a and 2b). In Experiment 3, 2.5 g/kg ethanol increased dopamine concentration in striatal tissue as well as locomotor activity in infant Wistar rats. Adding to our previous results showing a reduction in ethanol induced activity by a GABA B agonist or a nonspecific opioid antagonist, the present experiments implicate both D1-like and D2-like dopamine receptors in ethanol-induced locomotor stimulation during early development. According to these results, the same mechanisms that modulate ethanol-mediated locomotor stimulation in adult rodents seem to regulate this particular ethanol effect in the infant rat.

Similar withdrawal severity in adolescents and adults in a rat model of alcohol dependence

Alcohol use during adolescence leads to increased risk of developing an alcohol use disorder (AUD) during adulthood. Converging evidence suggests that this period of enhanced vulnerability for developing an AUD may be due to the adolescent's unique sensitivity and response to alcohol. Adolescent rats have been shown to be less sensitive to alcohol intoxication and withdrawal susceptibility; however, age differences in ethanol pharmacokinetics may underlie these effects. Therefore, this study investigated alcohol intoxication behavior and withdrawal severity using a modified Majchrowicz model of alcohol dependence that has been shown to result in similar blood ethanol concentrations (BECs) despite age differences. Adolescent (postnatal day, PND, 35) and adult rats (PND 70+) received ethanol according to this 4-day binge paradigm and were observed for withdrawal behavior for 17h. As expected, adolescents showed decreased sensitivity to alcohol-induced CNS depression as evidenced by significantly lower intoxication scores. Thus, adolescents received significantly more ethanol each day (12.3+/-0.1g/kg/day) than adults (9.2+/-0.2g/kg/day). Despite greater ethanol dosing in adolescent rats, both adolescent and adult groups had comparable peak BECs (344.5+/-10.2 and 338.5+/-7.8mg/dL, respectively). Strikingly, withdrawal severity was similar quantitatively and qualitatively between adolescent and adult rats. Further, this is the first time that withdrawal behavior has been reported for adolescent rats using this model of alcohol dependence. A second experiment confirmed the similarity in BECs at various time points across the binge. These results demonstrate that after consideration of ethanol pharmacokinetics between adults and adolescents by using a model that produces similar BECs, withdrawal severity is nearly identical. This study, in combination with previous reports on ethanol withdrawal in adolescents and adults, suggests only a BEC-dependent effect of ethanol on withdrawal severity regardless of age.

Ethanol-induced preferences or aversions as a function of age in preweanling rats

The reinforcing value of a relatively high ethanol dose (3 g/kg) administered intragastrically was investigated in preweanling rats. Ethanol intoxication on Postnatal Days 7-8 increased ethanol intake and enhanced the drug's palatability when tested 3 days later. In contrast, intoxication on Days 10-11 decreased ethanol intake and increased aversive responses to the drug. When reducing the delay between intoxication and test to 24 hr, the taste aversion was enhanced, whereas the preference was unaffected. Results suggest an ontogenetic change in pups' perception of the reinforcing value of ethanol that coincides with the end of a sensitive period for learning preferences in rats younger than 9 days old (T. L. Roth & R. M. Sullivan, 2003; R. M. Sullivan, M. Landers, B. Yeaman, & D. A. Wilson, 2000).

Binge ethanol exposure in late gestation induces ethanol aversion in the dam but enhances ethanol intake in the offspring and affects their postnatal learning about ethanol

Previous studies show that exposure to 1 or 2g/kg of ethanol during the last days of gestation increases ethanol acceptance in infant rats. We tested whether prenatal exposure to 3g/kg, a relatively high ethanol dose, generates an aversion to ethanol in both the dam and offspring, and whether this prenatal experience affects the expression of learning derived from ethanol exposure postnatally. The answer was uncertain, because postnatal administration of a 3-g/kg ethanol dose induces an aversion to ethanol after postnatal day (PD) 10 but increases ethanol acceptance when administered during the first postnatal week. In the present study, pregnant rats received intragastric administrations of water or ethanol (3g/kg) on gestation days 17-20. On PDs 7-8 or 10-11, the offspring were administered water or ethanol (3g/kg). Intake of ethanol and water, locomotor activity in an open field, and ethanol odor preference were evaluated in the pups, whereas the mothers were evaluated in terms of ethanol intake. Results indicated an aversion to ethanol in dams that had been administered ethanol during gestation, despite a general increase in ethanol intake observed in their pups relative to controls. The prenatal ethanol exposure also potentiated the increase in ethanol intake observed after intoxication on PDs 7-8. Ethanol intoxication on PDs 10-11 reduced ethanol consumption; this ethanol aversion was still evident in infant rats exposed prenatally to ethanol despite their general increase in ethanol intake. No effects of prenatal ethanol exposure were observed in terms of motor activity or odor preference. It is concluded that prenatal exposure to ethanol, even in a dose that induces ethanol aversion in the gestating dam, increases ethanol intake in infant rats and that this experience modulates age-related differences in subsequent postnatal learning about ethanol.

The role of GABA(A) receptors in the acute and chronic effects of ethanol: a decade of progress

The past decade has brought many advances in our understanding of GABA(A) receptor-mediated ethanol action in the central nervous system. We now know that specific GABA(A) receptor subtypes are sensitive to ethanol at doses attained during social drinking while other subtypes respond to ethanol at doses attained by severe intoxication. Furthermore, ethanol increases GABAergic neurotransmission through indirect effects, including the elevation of endogenous GABAergic neuroactive steroids, presynaptic release of GABA, and dephosphorylation of GABA(A) receptors promoting increases in GABA sensitivity. Ethanol's effects on intracellular signaling also influence GABAergic transmission in multiple ways that vary across brain regions and cell types. The effects of chronic ethanol administration are influenced by adaptations in GABA(A) receptor function, expression, trafficking, and subcellular localization that contribute to ethanol tolerance, dependence, and withdrawal hyperexcitability. Adolescents exhibit altered sensitivity to ethanol actions, the tendency for higher drinking and longer lasting GABAergic adaptations to chronic ethanol administration. The elucidation of the mechanisms that underlie adaptations to ethanol exposure are leading to a better understanding of the regulation of inhibitory transmission and new targets for therapies to support recovery from ethanol withdrawal and alcoholism.

Effects of neonatal alcohol exposure on vasoactive intestinal polypeptide neurons in the rat suprachiasmatic nucleus

Neonatal alcohol exposure produces long-term changes in the suprachiasmatic nucleus (SCN) that are presumably responsible for disturbances in the light-dark regulation of circadian behavior in adult rats, including the pattern of photoentrainment, rate of re-entrainment to shifted light-dark cycles, and phase-shifting responses to light. Because SCN neurons containing vasoactive intestinal polypeptide (VIP) receive direct photic input via the retinohypothalamic tract and thus play an important role in the circadian regulation of the SCN clock mechanism by light, the present study examined the long-term effects of neonatal alcohol exposure on VIP neuronal populations within the SCN of adult rats. Male Sprague-Dawley rat pups were exposed to alcohol (EtOH; 3.0, 4.5, or 6.0 g/kg/day) or isocaloric milk formula (gastrostomy control; GC) on postnatal days 4-9 using artificial-rearing methods. At 2-3 months of age, animals from the suckle control (SC), GC, and EtOH groups were exposed to constant darkness (DD) and SCN tissue was harvested for subsequent analysis of either VIP mRNA expression by quantitative polymerase chain reaction (PCR) and in situ hybridization or of VIP-immunoreactive (ir) neurons using stereological methods. Neonatal alcohol exposure had no impact on VIP mRNA expression but dramatically altered immunostaining of neurons containing this peptide within the SCN of adult rats. The relative abundance of VIP mRNA and anatomical distribution of neurons expressing this transcript were similar among all control- and EtOH-treated groups. However, the total number and density of VIP-ir neurons within the SCN were significantly decreased by about 35% in rats exposed to alcohol at a dose of 6.0 g/kg/day relative to that observed in both control groups. These results demonstrate that VIP neuronal populations in the SCN are vulnerable to EtOH-induced insult during brain development. The observed alterations in SCN neurons containing VIP may have an impact upon clock responses to light input and thus contribute to the long-term effects of neonatal alcohol exposure on the photic regulation of circadian behavior.

A novel herbal preparation desensitizes mesenteric afferents to bradykinin in the rat small intestine

Herbal preparations are evolving as promising agents for the treatment of functional gastrointestinal disorders which are considered to be secondary to visceral hypersensitivity. We aimed to determine whether a new combination of six herbal extracts reduces the sensitivity of intestinal afferents in rat. Male Wistar rats (250-350 g, n = 6 per group) were gavaged with either vehicle or 2.5, 5 or 10 mL kg(-1) of STW 5-II, a herbal preparation which contains six extracts. Two hours later, animals were anaesthetized and extracellular multi-unit mesenteric afferent nerve recordings were obtained in the proximal jejunum in vivo. Afferent discharge to 5-hydroxy-tryptamine (5-HT) (5, 10, 20 and 40 microg kg(-1), i.v.), luminal distension (0-60 mmHg) and bradykinin (BK) (15, 30 and 60 microg kg(-1), i.v.) was recorded. At baseline, spontaneous afferent discharge was not different following pretreatment with the various doses of STW 5-II compared with vehicle. The pressure-dependent increase in afferent discharge to intraluminal ramp distension and the dose-dependent increase in afferent firing following 5-HT were also uninfluenced by STW 5-II pretreatment. In contrast, the afferent nerve responses to 15, 30 and 60 microg kg(-1) of BK were reduced following 10 mL kg(-1) STW 5-II with peaks at 106 +/- 19, 153 +/- 22 and 156 +/- 25 imp s(-1) compared with 160 +/- 15, 228 +/- 14 and 220 +/- 16 imp s(-1) following vehicle pretreatment (mean +/- SEM, P < 0.05). Intestinal afferent sensitivity to BK which plays a prime role in nociception was reduced following STW 5-II. Thus, STW 5-II may be of therapeutic use for conditions that involve neuronal hypersensitivity and the release of BK in the intestine.

A single exposure to alcohol during brain development induces microencephaly and neuronal losses in genetically susceptible mice, but not in wild type mice

Maternal alcohol abuse during pregnancy can damage the fetal brain and lead to fetal alcohol syndrome (FAS). Despite public warnings discouraging alcohol use during pregnancy, many pregnant women continue to drink intermittently because they do not believe that occasional exposures to alcohol can be harmful to a fetus. However, because of genetic differences, some fetuses are much more susceptible than others to alcohol-induced brain injury. Thus, a relatively low quantity of alcohol that may be innocuous to most fetuses could damage a genetically susceptible fetus. Neuronal nitric oxide synthase (nNOS) can protect developing mouse neurons against alcohol toxicity by synthesizing neuroprotective nitric oxide. This study examined whether a single exposure to alcohol, which causes no evident injury in wild type mice, can damage the brains of mice genetically deficient for nNOS (nNOS-/- mice). Wild type and nNOS-/- mice received intraperitoneal injections of alcohol (0.0, 2.2, or 4.4mg/g body weight) either as a single dose on postnatal day (PD) 4 or as repeated daily doses over PD4-9. Brain volumes and neuronal numbers within the hippocampus and cerebral cortex were determined on PD10. Alcohol exposure on PD4-9 restricted brain growth and caused neuronal death in both strains of mice, but the severity of microencephaly and neuronal loss were more severe in the nNOS-/- mice than in wild type. The 4.4 mg/g alcohol dose administered on PD4 alone caused significant neuronal loss and microencephaly in the nNOS-/- mice, while this same dose caused no evident injury in the wild type mice. Thus, during development, a single exposure to alcohol can injure a genetically vulnerable brain, while it leaves a wild type brain unaffected. Since the genes that confer alcohol resistance and vulnerability in developing humans are unknown, any particular human fetus is potentially vulnerable. Thus, women should be counseled to consume no alcohol during pregnancy.

Ethanol induces locomotor activating effects in preweanling Sprague-Dawley rats

Abuse of drugs exerts biphasic motor activity effects, which seem to be associated with their motivational effects. In the case of ethanol, heterogenous rat strains appear to be particularly sensitive to the sedative effects of the drug. In contrast, ethanol's activating effects have been consistently reported in rats genetically selected for ethanol affinity. Heightened ethanol affinity and sensitivity to ethanol's reinforcement are also observed in nonselected rats during early ontogeny. In the present study, we examined psychomotor effects of ethanol (1.25 and 2.5 g/kg) in 8-, 12-, and 15-day-old pups. Motor activity in a novel environment was assessed 5-10 or 15-20 min following drug treatment. Rectal temperatures and latency to exhibit the righting reflex were recorded immediately after locomotor activity assessment. Ethanol exerted clear activating effects at 8 and 12 days of age (Experiments 1a and 1b) and to a lesser extent at 15 days. At this age, ethanol enhanced locomotor activity in the first testing interval (Experiment 1b) and suppressed locomotion at 15-20 min (Experiment 1a). Ethanol-mediated motor impairment was more pronounced in the youngest group (postnatal day 8) than in the older ones. Blood ethanol concentrations were equivalent in all age groups. The present study indicates that preweanling rats are sensitive to ethanol's stimulating effects during the second postnatal week, and suggest that specific periods during early ontogeny of the rat can provide a valuable framework for the study of mechanisms underlying ethanol's stimulation and reinforcement effects.