Adolescent and adult rat cortical protein kinase A display divergent responses to acute ethanol exposure

Adolescent rats display reduced sensitivity to many dysphoria-related effects of alcohol (ethanol) including motor ataxia and sedative hypnosis, but the underlying neurobiological factors that contribute to these differences remain unknown. The cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) pathway, particularly the type II regulatory subunit (RII), has been implicated in ethanol-induced molecular and behavioral responses in adults. Therefore, the current study examined cerebral cortical PKA in adolescent and adult ethanol responses. With the exception of early adolescence, PKA RIIα and RIIβ subunit levels largely did not differ from adult levels in either whole cell lysate or P2 synaptosomal expression. However, following acute ethanol exposure, PKA RIIβ P2 synaptosomal expression and activity were increased in adults, but not in adolescents. Behaviorally, intracerebroventricular administration of the PKA activator Sp-cAMP and inhibitor Rp-cAMP prior to ethanol administration increased adolescent sensitivity to the sedative-hypnotic effects of ethanol compared to controls. Sp-cAMP was ineffective in adults whereas Rp-cAMP suggestively reduced loss of righting reflex (LORR) with paralleled increases in blood ethanol concentrations. Overall, these data suggest that PKA activity modulates the sedative/hypnotic effects of ethanol and may potentially play a wider role in the differential ethanol responses observed between adolescents and adults.     

Contrasting effects of acute and chronic ethanol administration on rat liver tyrosine aminotransferase

We compared the effects of acute and chronic ethanol administration on the activity and synthesis of tyrosine aminotransferase (TAT) in rat liver. In acute experiments, chow-fed rats received a single dose of either ethanol (6 g/kg body wt.) or saline. In chronic studies, rats were pair-fed liquid diets containing either ethanol (36% of calories) or isocaloric maltose-dextrin for 6–8 weeks. In rats acutely fed ethanol, the relative rate of TAT synthesis was more than twofold higher than in saline-treated controls. In rats subjected to chronic ethanol administration, both the TAT activity and synthesis rate were the same as in pair-fed controls, but both these parameters in the two groups were equal to those in animals given acute ethanol acutely. These findings indicate that whereas acute ethanol administration was associated with a stimulation of TAT synthesis, long-term ethanol administration was not. The data suggest that ethanol itself does not directly induce TAT. Rather, enzyme synthesis is regulated by one or more endogenous secondary effector(s) whose production is influenced differently by acute or chronic ethanol feeding.     

Activation of neutral sphingomyelinase participates in ethanol-induced apoptosis in Hep G2 cells

The mechanism underlying ethanol-induced apoptosis in liver cells is not clear. Sphingomyelin (SM) metabolism is a novel signal transduction pathway that has an impact on apoptosis in many cell types. We investigated whether the SM pathway is involved in ethanol-induced apoptosis in the liver. Hep G2 cells were treated with ethanol followed by assaying apoptosis, sphingomyelinase (SMase) activity, caspase-3 activity, and the changes of SM content in the cells. We found that ethanol dose-dependently increased apoptosis and the effect was accompanied by increases of caspase-3 activity and neutral SMase activity. At concentrations of 80 and 160 mM, ethanol significantly increased caspase-3 activity by 120% and neutral SMase activity by 24%. The activity of acid SMase was only slightly increased without statistical significance. C(2)-ceramide, the exogenous SM metabolite, mimicked the effects of ethanol on apoptosis and caspase-3 activation. When the SM content was determined 24 h after treatment with ethanol, its level was 15% lower than that of controls. The results indicate that metabolism of SM triggered by neutral SMase participates in ethanol-induced apoptosis in Hep G2 cells and activation of caspase-3 is involved in the apoptotic pathway.     

Taurine modulates catalase, aldehyde dehydrogenase, and ethanol elimination rates in rat brain

Chronic administration of either the sulphonated amino acid taurine (0.32 or 0.62 g/kg for 2 weeks) or the catalase inhibitor, 3-amino, 1,2,4-triazole (AT: 0.5 or 1.0 g/kg for 5 days) significantly reduced catalase activities both in the brain and liver of male Wistar rats. The total brain activity of aldehyde dehydrogenase was significantly increased after the lower dose of taurine and after administration of both doses of AT. Hepatic alcohol dehydrogenase activity was not altered by either AT or taurine administration. In taurine-supplemented rats, a significant increase in the ethanol elimination rates (EER) was discernible in the livers after a 2 g/kg dose of ethanol. In contrast, significant decreases in the EER were observed in both plasmas and livers of rats in which catalase was inhibited by AT. However, the brain EERs were comparable in both catalase-inhibited and taurine-supplemented rats, both showing a decrease by comparison to controls. The similar psychopharmacological effects induced by both of these compounds on ethanol-induced effects might indicate that this is mediated in part via the catalase pathway. Since both catalase and the EERs are diminished in the brain after the administration of either of these compounds, this may be an important factor in the moderation of ethanol-induced behaviour.     

Autonomic responses to ethanol in adolescent and adult rats: a dose-response analysis

Athough the exact cause of the increase in ethanol consumption during adolescence is not known, age differences in sensitivity to some of ethanol's effects may play a contributory role. Prior research has shown little difference in the expression of ethanol-induced tachycardia between adolescents and adults following ethanol inhalation. In contrast, there is mounting evidence of ontogenetic differences in ethanol-induced hypothermia, although the nature of the ontogenetic effect observed has been found to vary across studies and even within labs. Relative ontogenetic differences in body temperature (BT) after ethanol administration appear to be driven in part by the amount of experimental perturbation associated with the test protocol, although differing ethanol exposure levels across studies may also have contributed to the variations in ontogenetic patterns that have been observed. To explore the latter possibility, the present study assessed ethanol-induced hypothermia and tachycardia in adolescent and adult male Sprague-Dawley rats examined in their home cages in the presence of their housing partner following intraperitoneal administration of 0.5, 1.5, or 3.0 g/kg ethanol. The results showed that, although adolescents did not show an adult-typical tachycardic effect at any dose, they proved more sensitive than adults to ethanol's hypothermic effects at the two highest doses. These findings suggest that not only the degree of experimental perturbation, but also the amount of ethanol exposure may differentially effect expression of age differences in ethanol-induced hypothermia, with adolescents showing greater hypothermia than adults at higher doses. Together with previous findings, these data contribute to the emerging picture that age differences in autonomic effects of ethanol appear to be particularly sensitive to dosing parameters and experimental protocols, unlike the generally more consistent ontogenetic findings observed across studies when using behavioral measures of ethanol sensitivity.     

Effects of naltrexone on the ethanol-induced changes in the rat central dopaminergic system

AIMS: The opioid antagonist naltrexone may reduce ethanol reward, but the underlying neurochemical mechanisms has yet to be clarified. The afferent projections to the nucleus accumbens from the ventral tegmental area (VTA) provide a potential substrate by which endogenous opioids may modulate the dopaminergic rewarding effects of ethanol. We assessed mRNA levels of tyrosine hydroxylase (TH), a major regulatory enzyme in the dopamine synthesis and levels of dopamine and its metabolites after chronic ethanol administration with and without concomitant naltrexone. METHODS: Sprague-Dawley rats were exposed to chronic ethanol consumption (5%, 4 weeks) with and without concomitant naltrexone administration. Levels of TH mRNA in the VTA and substantia nigra (SN) and dopamine and its metabolites in the striatum of the rats were measured by in situ hybridization and by high performance liquid chromatography, respectively. RESULTS: Chronic ethanol consumption increased TH mRNA levels in the VTA, but did not cause any significant change in the SN. With naltrexone treatment, ethanol-induced increase in the TH mRNA level was reduced in the VTA. Chronic ethanol consumption did not cause any change in the levels of dopamine and its metabolites in most brain regions. Only in the striatum, ethanol consumption with naltrexone treatment significantly increases the dopamine level. CONCLUSION: This finding supports the presence of interactions of opioid and dopaminergic systems in the VTA in mediating ethanol reward, and thus naltrexone attenuates the rewarding properties of ethanol by interfering with the ethanol-induced stimulation of the mesolimbic dopaminergic pathway.     

Ethanol increases phosphodiesterase 4 activity in bovine bronchial epithelial cells.

Ethanol exposure in airway epithelium increases cyclic AMP (cAMP)-dependent protein kinase (PKA) activity. Activation of PKA and cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG) has been shown to increase ciliary beat frequency (CBF) in bovine bronchial epithelial cells (BBECs). We have shown that biologically relevant concentrations of ethanol stimulate increases in CBF in a nitric oxide-dependent manner, mediated through elevated cAMP levels and subsequent PKA activation. This ethanol-driven rapid and transient increase in CBF occurs 15 to 30 min after exposure to 100 mM ethanol. However, after prolonged exposure to 100 mM ethanol (>/=6 h), CBF and the catalytic activity of PKA return to baseline levels. We hypothesize that cyclic nucleotide-dependent phosphodiesterase (PDE) activity attenuates the duration of ethanol-stimulated ciliary motility. The effect of ethanol on the PDE activity in BBECs was determined through direct assay of catalytic activity. When BBECs were incubated with 100 mM ethanol, significant increases in cAMP levels occurred within 1 h, with corresponding increases in PKA activity. Treatment of BBECs with 100 mM ethanol increased cAMP-PDE activity significantly by 4 h. 3-Isobutyl-1-methylxanthine, Ro 20-1724, and rolipram inhibited ethanol-stimulated cAMP-PDE activity. These agents inhibited ethanol-stimulated cAMP-PDE activity and increased the magnitude of ethanol-stimulated PKA activity observed under the same conditions. These findings support the idea that acute exposure (<6 h) to ethanol increases cAMP levels, and the associated increase in PKA activation is regulated by cAMP-dependent PDE, specifically PDE4. Other compensatory mechanisms however, may be responsible for the down-regulation of PKA, which occurs after chronic epithelial exposure (>/=6 h) to ethanol.     

Vitamin B12 deficiency results in the abnormal regulation of serine dehydratase and tyrosine aminotransferase activities correlated with impairment of the adenylyl cyclase system in rat liver

The aim of the present study was to elucidate the mechanism of the vitamin B(12) deficiency-induced changes of the serine dehydratase (SDH) and tyrosine aminotransferase (TAT) activities in the rat liver. When rats were maintained on a vitamin B(12)-deficient diet, the activities of these two enzymes in the liver were significantly reduced compared with those in the B12-sufficient control rats (SDH 2.8 (sd 0.56) v. 17.5 (sd 6.22) nmol/mg protein per min (n 5); P < 0.05) (TAT 25.2 (sd 5.22) v. 41.3 (sd 8.11) nmol/mg protein per min (n 5); P < 0.05). In the B(12)-deficient rats, the level of SDH induction in response to the administration of glucagon and dexamethasone was significantly lower than in the B(12)-sufficient controls. Dexamethasone induced a significant increase in TAT activity in the primary culture of the hepatocytes prepared from the deficient rats, as well as in the cells from the control rats. However, a further increase in TAT activity was not observed in the hepatocytes from the deficient rats, in contrast to the cells from the controls, when glucagon was added simultaneously with dexamethasone. The glucagon-stimulated production of cAMP was significantly reduced in the hepatocytes from the deficient rats relative to the cells from the control rats. Furthermore, the glucagon-stimulated adenylyl cyclase activity in the liver was significantly lower in the deficient rats than in the controls. These results suggest that vitamin B(12) deficiency results in decreases in SDH and TAT activities correlated with the impairment of the glucagon signal transduction through the activation of the adenylyl cyclase system in the liver.     

Nicotine enhances ethanol-induced fat accumulation and collagen deposition but not inflammation in mouse liver

Introduction

Alcohol and tobacco are frequently co-abused. Tobacco smoke increases alcoholic steatosis in apoE(−/−) mice. Tobacco smoke contains more than 4000 chemicals, but it is unknown which compounds in tobacco smoke play a major role in increasing alcoholic steatosis.

Methods

C57BL/J6 mice were intraperitoneally injected with nicotine at 1 mg/kg every day or saline at the same volume as a control and the mice were fed dextrose-control or ethanol Lieber–DeCarli liquid diets. Three weeks later the mice were sacrificed after overnight fasting.

Results

Neither nicotine injection nor ethanol feeding alone increased serum levels of triglyceride, but the combination of nicotine and ethanol increased serum levels of triglyceride. Both nicotine injection alone and ethanol feeding alone increased hepatic collagen type I deposition, and nicotine injection and ethanol feeding combined further increased hepatic collagen type I deposition. The combination of nicotine and ethanol also activated hepatic stellate cells, a principal liver fibrogenic cell. Hepatic fat accumulation was induced by ethanol feeding, which was further enhanced by nicotine injection. Ethanol feeding caused an increase in serum ALT, but nicotine did not further increase serum ALT levels. Lipid droplets and inflammatory foci were observed in liver sections from ethanol-fed mice; nicotine treatment increased the number and size of lipid droplets, but not the number and size of inflammatory foci. Nicotine did not further increase ethanol-induced hepatic neutrophil infiltration.

Conclusions

These results suggest that nicotine enhances ethanol-induced steatosis and collagen deposition, but nicotine has no effect on ethanol-induced inflammation.     

Role of ascorbic acid on tyrosine hydroxylase activity in the adrenal gland of guinea pig.

The decrease of tyrosine hydroxylase activity in adrenal homogenate in scurvy was recovered after the administration of ascorbic acid. The causes of the increase in the enzyme activity after the administration of ascorbic acid have been studied. 1. No significant elevation in the enzyme activity was observed after the administration of reserpine to the scortutic guinea pig. 2. A dose of metal chelating agent, alpha, alpha'-dipyridyl, prevented the ascorbic acid-induced or reserpine-induced increase in enzyme activity in the scorbutic and the non-scorbutic guinea pigs, respectively. 3. Tyrosine hydroxylase activity was partially recovered by the administration of FeSO4 to the scorbutic guinea pig. From these results, it became clear that the induction of tyrosine hydroxylase which was not observed in scurvy was due to the deficiency of Fe2+. These results suggested that ascorbic acid affected the induction of this enzyme via Fe2+.     

Lack of aldehyde dehydrogenase ameliorates oxidative stress induced by single-dose ethanol administration in mouse liver.

Polymorphism of aldehyde dehydrogenase 2 (ALDH2), denoted ALDH2*2, is far more common in East Asian countries. Acetaldehyde, an intermediate metabolite of ethanol, is metabolized very slowly in people who have ALDH2*2, as the mutated ALDH2 lacks acetaldehyde metabolizing activity. On the other hand, it is well established that metabolism of ethanol causes oxidative stress in liver tissue. To examine the consequences of this polymorphism on ethanol-induced oxidative stress in liver tissue, we conducted a study using Aldh2 knockout mice. Aldh2+/+ and Aldh2-/- mice were orally administered ethanol at a dose of 5g/kg body weight. Levels of malondialdehyde, an indicator of oxidative stress, and glutathione, a key antioxidant, in liver tissue were analyzed 0-24h after administration. Levels of malondialdehyde were significantly lower in Aldh2-/- mice than in Aldh2+/+ mice at 12h after injection, while levels of glutathione were higher in Aldh2-/- mice than in Aldh2+/+ mice at 6 and 12h after injection. Our results suggest that a lack of ALDH ameliorates ethanol-induced oxidative stress in liver tissue.     

The role of adenosine A1 receptor activation in ethanol-induced inhibition of stimulated glutamate release in the hippocampus of the fetal and adult guinea pig

The role of adenosine A₁ receptor activation in ethanol-induced inhibition of stimulated l-glutamate (Glu) release was determined in transverse hippocampal slices of the near-term fetal guinea pig and the adult guinea pig. Exposure of the slices to 48 mM ethanol inhibited K⁺-stimulated Glu efflux. Pretreatment with 8-cyclopentyltheophylline (CPT), a selective adenosine A₁ receptor antagonist, blocked the ethanol-induced inhibition of K⁺-stimulated Glu efflux in the near-term fetal and adult hippocampus. In the near-term fetus, 2-chloro-N⁶-cyclopentyladenosine (CCPA), a selective adenosine A₁ agonist, and exogenous adenosine each blocked K⁺-stimulated Glu efflux similar to that produced by 48 mM ethanol. In the adult, although K⁺ increased Glu efflux in the presence of CCPA or adenosine, the magnitude of increase was less than that of the K⁺-stimulated Glu efflux for the control condition. Exposure to ethanol alone or ethanol plus CPT produced a transient increase in endogenous adenosine efflux in the near-term fetal and adult hippocampus, which was not temporally related to the ethanol-induced inhibition of K⁺-stimulated Glu efflux. Overall, the data indicate that adenosine A₁ receptor activation mediates ethanol-induced inhibition of stimulated Glu release in the hippocampus of the near-term fetal and adult guinea pig.     

Low levels of ethanol stimulate and high levels decrease phosphorylation in microtubule-associated proteins in rat brain: an in vitro study

Phosphorylation and dephosphorylation of proteins associated with microtubules (MAPs) modulate the functional properties of microtubules (MT). A study was designed to test the hypothesis that ethanol at pharmacologically relevant levels affects phosphorylation of MAPs. Low (6, 12, 24, and 48 mM) and high (96, 384, and 768 mM) levels of ethanol were used in the study. MT prepared from rat brain by successive cycles of assembly-disassembly were found to contain two high molecular weight proteins (MAP2 and MAP1), tubulin, and 70-kDa neurofilament. The kinase activity was determined using [gamma(32)P]ATP as a phosphate donor. The results showed that ethanol primarily stimulated MAP2 phosphorylation. Low levels of ethanol stimulated, whereas high levels decreased, the kinase activity. MAP1 was phosphorylated to a lesser extent. 70-kDa neurofilament and tubulin were phosphorylated, however, the dose-dependent biphasic effect of ethanol on phosphorylation was not found in these cytoskeleton proteins. To determine whether the ethanol-induced kinase activity was cAMP-dependent, the catalytic subunit of cAMP-dependent protein kinase was isolated, purified, and kinase activity was determined with and without ethanol. The results showed that cAMP was not involved in ethanol-induced kinase activity. We conclude that ethanol predominantly stimulates phosphorylation of MAP2 in a dose-dependent manner.     

INCREASE IN RAT LIVER TRYPTOPHAN OXYGENASE ACTIVITY AFTER ACUTE ETHANOL TREATMENT: DEPENDENCE ON FEEDING STATE AND ROUTE OF ETHANOL ADMINISTRATION

A time course and dose-response study of the effects of acuteethanol administration on the activlty of liver tryptophan oxygenasewas carried out in fed and starved rats. Ethanol doses rangingfrom 0.5 to 5.0 g/kg body weight were given either intragastricallyor intraperitoneally. In a detailed time curve for an oral 3.3g/kg dose of ethanol in starved rats, the total activity oftryptophan oxygenase was increased 1.5-fold 2 hr after ethanoladministration and the activity of the holoenzyme (haem-saturatedform) increased one hour later, thus indicating that increasedhaem-saturation is not the critical stimulus for accumulationof the enzyme after acute ethanol ingestion. Both the totaland holoenzyme activities reached a peak, whlch was4.5–5.5times the control activity, 5–6 hr after ethanol treatment.The increase in the enzyme activities was not directly dependenton the dose of ethanol, but rather the peak blood ethanol concentration,which had to reach a critical level to trigger enzyme activation.In fed rats when ethanol was given orally, this critical bloodethanol level was not achieved even with the highest ethanoldose and no significant increases in tryptophan oxygenax activitieswere seen. 4-Methylpyrazole (75 mg/kg) inhibited the ethanol-inducedincrease in the total tryptophan oxygenase actlvity by 30%,but did not affect that in the holoenzyme activity. Cyanamide(5 mg/kg) did not affect the ethanol-induced increases in eithertotal enzyme or holoenzyme activities. t-Butanol (1.0 g/kg)caused increases of the same order of magnitude as ethanol did.It was concluded that 70% of the increase in total tryptophanoxygenase activity after acute ethanol ingestion is probablycaused by an action of ethanol itself. while 30% may be causedby ethanol metabolism. However, the increase in haem-saturationwas apparently caused by an action of ethanol itself.     

Acute ethanol treatment increases level of progesterone in ovariectomized rats.

To determine whether an increased level of progesterone in adult female rats after acute ethanol treatment, described previously in our study, is the result of activation of adrenal glands, we analyzed adrenal cortex morphologically and measured serum levels of corticosterone and progesterone in ovariectomized rats. In addition, a possible involvement of the opioid system in an observed phenomenon was tested. Adult female Wistar rats were ovariectomized, and 3 weeks after surgery they were treated intraperitoneally with (a) ethanol (4 g/kg), (b) naltrexone (5 mg/kg), followed by ethanol (4 g/kg) 45 min later, and (c) naltrexone (5 mg/kg), followed by saline 45 min later. Untreated and saline-injected rats were used as controls. The animals were killed 0.5 h after ethanol administration. Morphometric analysis was carried out on paraffin sections of adrenal glands, stained with hematoxylin-eosin, and the following parameters were determined: absolute volume of the zona glomerulosa, the zona fasciculata, and the zona reticularis; numerical density, volume, and the mean diameter of adrenocortical cells and of their nuclei; and mean diameter and length of capillaries. The results showed that acute ethanol treatment significantly increased absolute volume of the zona fasciculata and length of its capillaries but did not alter other stereological parameters. Also, serum levels of corticosterone and progesterone were enhanced. Pretreatment with naltrexone had no effect on ethanol-induced changes. These findings are consistent with our previous hypothesis that an ethanol-induced increase of the progesterone level in adult female rats originates from the adrenal cortex.     

Verapamil effects on physiological and behavioral responses to ethanol in the rat

Experiments were performed to determine the ability of verapamil to reverse ethanol-induced hypothermia and behavioral changes. Permanent cannulae for intracerebroventricular (i.c.v.) infusion were implanted bilaterally in rats following standard stereotaxic procedures. Following post-operative recovery, either verapamil or artificial cerebral spinal fluid (ACSF) was infused i.c.v., followed by 4.0 g/kg ethanol in saline administered by intragastric gavage. Changes in body temperature and overall activity were monitored. In another series of experiments, rats were given either i.c.v. verapamil or ACSF followed by 1.5 g/kg intraperitoneal ethanol. Ability to turn over and open-field activity were monitored. In addition, to investigate the action of verapamil alone on body temperature, rats were infused i.c.v. either with verapamil or control ACSF, followed by intragastric administration of a volume of saline equal to 4.0 g/kg ethanol (20% v/v). At an ambient temperature of 22 degrees C, verapamil, infused prior to ethanol administration, significantly and rapidly attenuated the thermolytic action of ethanol. Central administration of verapamil alone did not induce a significant change in body temperature until more than 1.5 hr after injection, at which time temperature began to gradually increase. Pretreatment with verapamil induced significantly faster recovery from ethanol-induced changes in overall activity. Only a non-significant reversal of ethanol's effects on open-field activity and time taken to turn over occurred. These results demonstrate that verapamil can significantly antagonize ethanol-induced hypothermia and possibly motor disturbances in rats, leading us to postulate the possible involvement of neuronal Ca2+ channels in these effects of ethanol.     

Abamectin attenuates gastric mucosal damage induced by ethanol through activation of vagus nerve in rats.

Some type A gamma-aminobutyric acid (GABA(A)) receptor agonists are effective in protecting against the formation of stomach lesions induced by ethanol. Natural product abamectin, one of the existing GABA(A) receptor agonists, might protect against the development of gastric ulcers induced by ethanol. We investigated the protective effect of abamectin against the formation of gastric mucosal lesions induced by ethanol in rats. Abamectin (3 mg/kg, p.o.) was given to rats 1 h before administration of ethanol [4 ml of a 30% (volume/volume) solution]. Mucosal lipid peroxidation (LPO), nitric oxide (NO) levels, and ulcer index were measured 3 h after gastric surgery (vagotomy vs. sham vagotomy) in treated versus control subjects. Abamectin attenuated ethanol-induced gastric ulceration, decreased LPO regeneration, and increased NO production in the gastric mucosa of rats in the sham vagotomy group. However, this protective effect of abamectin against ethanol-induced gastric lesions was not observed in rats in the group that underwent vagotomy. These results support the suggestion that administration of abamectin ameliorated the ethanol-induced gastric mucosal injury through elevation of NO production. Activation of the vagus nerve may be involved in the abamectin-associated gastric protection against the effects of ethanol in rats.     

Modulating effects of biogenic amines on calcium and ethanol-induced sleeping time

The present study was carried out in order to clarify the mechanism of calcium prolongation of ethanol-induced sleep. p-Chlorophenylalanine (PCPA, 300 mg/kg), alpha-methyltyrosine (alpha MPT, 100 mg/kg) and diethyldithiocarbamate (DDC, 250 mg/kg) were administered intraperitoneally (IP) to mice to reduce the levels of serotonin (5-HT), dopamine (DA) and norepinephrine (NE) respectively in the brain. Sleeping time was then measured following the administration of ethanol (4.5 g/kg, IP) both with and without CaCl2 (20 mumol/kg, intravenous (IV)). When saline (IP) plus CaCl2 (IV) was administered, the duration of ethanol-induced sleep was prolonged by 100% as compared with saline (IP) plus saline (IV). Duration of ethanol-induced sleep was not changed by PCPA, alpha MPT and DDC. On the other hand, the prolongation of ethanol-induced sleep by CaCl2 was antagonized by PCPA, alpha MPT and DDC. Also, only the DA level in the cerebrum was increased by 25% by administration of CaCl2. We suggest that the increase in ethanol-induced sleeping time due to CaCl2 results from the increase in biogenic amines in the brain.     

Effect of ethanol on brain catecholamines in rat lines developed for differential ethanol-induced motor impairment

The importance of the central catecholamines, with the emphasis on the noradrenergic neurons in the differential sensitivity to ethanol between the AT (alcohol-tolerant) rats selected for low and the ANT (alcohol-nontolerant) rats selected for high sensitivity to ethanol-induced (2 g/kg) motor impairment, was clarified by studying the effects of ethanol (2 and 4 g/kg, IP) on the utilization of norepinephrine (NA) and dopamine (DA), and on the metabolism of NA. The utilization of the catecholamines was estimated from the disappearance of the amines after inhibition of the brain tyrosine hydroxylase by alpha-methyl-p-tyrosine (200 mg/kg, IP), given 15 min after the administration of ethanol. The formation of 3-methoxy-4-hydroxy-phenylglycol (MHPG) was used as an estimate of NA metabolism, and was measured 30 min after the administration of ethanol. The basal utilization rate of NA and DA was similar between the two rat lines, but the increased formation of MHPG suggested that the naive AT rats had a higher noradrenergic activity in the limbic forebrain, hypothalamus, and cerebellum than did ANT rats. In the brain of both lines, ethanol accelerated the utilization and metabolism of NA in the same manner. Ethanol also increased the utilization of DA in the limbic forebrain of the AT and ANT rats. The higher sensitivity of the ANT rats' DA neurons to ethanol in the limbic forebrain and striatum was revealed by the significant rat line X ethanol interaction. The present findings suggest that the AT and ANT rats differ in the dopaminergic, but not in the noradrenergic responses to ethanol.     

Positive allosteric modulation of the GABAB receptor by GS39783 attenuates the locomotor stimulant actions of ethanol and potentiates the induction of locomotor sensitization

Acute ethanol-induced locomotor stimulation and ethanol-induced locomotor sensitization are two behavioral assays thought to model the rewarding effects of ethanol. Recent evidence suggests that GS39783, a GABA_B positive allosteric modulator, may be effective at reducing both the rewarding and reinforcing effects of several drugs of abuse, including ethanol. The goal of this study was to determine if GS39783 was capable of altering acute ethanol-induced stimulation, and the induction and expression of ethanol-induced locomotor sensitization, without effecting basal locomotion levels. Several doses of GS39783 (ranging from 0 to 100 mg/kg, depending on experiment) were tested on adult male DBA/2J mice in four experiments using 3-day basal locomotion and acute ethanol stimulation paradigms, and 14-day induction and expression of ethanol sensitization paradigms. The results of experiment 1 are in agreement with current literature, suggesting that 30 mg/kg doses of GS39783 and lower do not alter basal locomotor activity. In experiment 2, we found that GS39783 significantly decreased acute ethanol stimulation, but only at the 30 mg/kg dose, supporting our hypothesis and other publications suggesting that GABA_B receptors modulate acute ethanol stimulation. Contrary to our hypothesis, GS39783 did not alter the expression of locomotor sensitization. Additionally, repeated administration of GS39783 in conjunction with ethanol unexpectedly potentiated ethanol-induced locomotor sensitization. Further study of GS39783 is warranted as it may be a more tolerable treatment for alcoholism than full agonists, due to its behavioral efficacy at doses that lack sedative side effects. Our results add to current literature suggesting that the GABA_B receptor system is indeed involved in the modulation of ethanol-induced locomotor stimulation and sensitization.