Effects of ethanol and ethanol withdrawal on nociception in rats

The effect of acute and chronic administration of ethanol and ethanol withdrawal on a radiant heat tail-flick assay of nociception was examined in rats. Acute administration of ethanol (2.0 g/kg, i.p.) produced peak antinociception (68% of maximum) by 30 min, and effects were gone by 120 min. Cumulative doses of ethanol (0.5-2.0 g/kg, i.p.) produced dose-dependent increases in latencies to 49% of maximum. During chronic administration, a liquid diet containing ethanol (6.5%) was given for 10 days. Tail-flick latencies were measured on day 0 (baseline), day 2, 4, 6, 8, and 10 of chronic ethanol and at 3, 6, 12, and 36 hr after removal of ethanol. To test for behavioral tolerance, both between- and within-group designs were used. In both between- and within-group experiments, the antinociceptive effects of chronic ethanol peaked by day 4 of exposure to the liquid diet, and tolerance developed by day 10. When the liquid diet was removed, hyperalgesia was detected at 6 and 12 hr after withdrawal, and was gone by 36 hr after withdrawal. When cumulative doses of ethanol (0.5-2.0 g/kg) were administered starting 12 hr after withdrawal, ethanol (0.5 g/kg) fully reversed the hyperalgesia induced by ethanol withdrawal, even though this dose was without antinociceptive effect in the absence of withdrawal. Higher doses of ethanol during ethanol withdrawal did not increase tail-flick latencies over baseline. In summary: (1) ethanol produces antinociception when administered acutely or chronically; (2) tolerance to the antinociceptive effects develops during chronic administration; (3) ethanol withdrawal induced hyperalgesia, which was reversed by ethanol; and (4) repeated testing did not produce behavioral tolerance.     

Effects of benzodiazepines on acute and chronic ethanol-induced nociception in rats

BACKGROUND: Acute and chronic ethanol produces antinociception, and ethanol withdrawal induces hyperalgesia. METHODS: A radiant heat tail-flick assay was used to assess the effects of benzodiazepine ligands on ethanol-induced changes in nociception in rats. Acute activity of cumulative doses of ethanol (0.5-2.0 g/kg) and diazepam (0.1-10 mg/kg), a benzodiazepine agonist, was tested alone and after pretreatment with flumazenil (1.0-10 mg/kg), a benzodiazepine antagonist. Chronic effects of ethanol were tested in three groups of rats that received a liquid diet for 10 days. One group received ethanol alone; one group received ethanol and twice-daily injections of flumazenil (10 mg/kg); and one received a dextrin control diet. Acute withdrawal was tested at 12 hr after removal of the liquid diet. Effects of cumulative doses of diazepam (1.0-10 mg/kg) were tested during withdrawal (12 hr) in the ethanol-alone group. RESULTS: Acute doses of ethanol produced a small but significant degree of antinociception, which was fully suppressed by flumazenil. Acute doses of diazepam did not produce antinociception. Chronic exposure to ethanol produced antinociception on days 2 through 8. Tolerance developed by day 10, and hyperalgesia was seen 12 hr after removal of ethanol. Administration of diazepam or ethanol during withdrawal reversed the hyperalgesia induced by ethanol withdrawal. However, flumazenil (10-50 mg/kg) failed to reverse the antihyperalgesic effect of either diazepam or ethanol. No antinociception was seen in either the ethanol/flumazenil or dextrin control groups. CONCLUSIONS: These results suggest that the antinociceptive effects of both acute and chronic ethanol are at least partially mediated by GABA receptors, and that diazepam's antihyperalgesic effects may not be mediated by the GABA acid receptor.     

Effects of Dihydropyridines on the Components of the Ethanol Withdrawal Syndrome: Possible Evidence for Involvement of Potassium,as Well as Calcium?

Comparison was made of the ability of two dihydropyridine calcium channel antagonists, nitrendipine and felodipine, to prevent a range of signs of ethanol withdrawal. The increases in handling-induced behavior seen in mice during withdrawal from chronic ethanol treatment were prevented by administration of nitrendipine, 50 mg/kg, but not by, felodipine, 10 mg/kg, a dose that caused a similar displacement of dihydropyridine binding in central nervous system tissue, in vivo and in vitro. A higher dose of felodipine, 20 mg/kg, also had no effects. Nitrendipine, but not felodipine, prevented audio-genic seizures during the withdrawal phase. Similarly, nitrendipine prevented both the decrease in thresholds for N -methyl-dl-aspartate seizures and the increase in thresholds for convulsions due to 4-aminopyridine, which were seen during the withdrawal period, while felodipine did not alter either of these changes. Withdrawal from the ethanol chronic treatment increased the thresholds to seizures produced by intravenous aminophylline; this change was also prevented by nitrendipine. The significance of this increase in thresholds was lost after felodipine administration. In naive mice (not treated with ethanol) the doses of nitrendipine and felodipine used in the withdrawal studies were tested against the effects of convulsant drugs. Both dihydropyridines increased, to similar extents, the thresholds for seizures produced by bicuculline, pentylenetetrarol, and by N- methyl-dl-aspartate. The thresholds for aminophylline were unaltered by either dihydropyridine. In contrast, the thresholds for seizures due to 4-aminopyn'dine in the naive animals were not changed by felodipine, but were increased by nitrendipine. The results suggest that changes in potassium, as well as calcium, may possibly be involved in some of the stages of the ethanol withdrawal syndrome. Key Words: Ethanol Withdrawal, Dihydropyridine, Calcium, Potassium, Seizures.     

Comparison of nitrendipine with propranolol and its use in combined cardiovascular therapy

New antihypertensive agents with favorable hemodynamic and metabolic profiles have resulted in reappraisal of traditional step-care therapy using diuretics and beta blockers. Calcium channel blockers are among the new antihypertensive agents that offer better hemodynamic effect compared with beta blockers, and they do not have unwanted metabolic effects as do diuretics. Calcium channel blockers, such as nitrendipine, are effective as monotherapy and in combination with other antihypertensive agents, and are particularly useful in elderly, black and low-renin patients. Preliminary results from a multicenter, double-blind, randomized, parallel study comparing nitrendipine with propranolol in patients over 40 demonstrate similar blood pressure-lowering effectiveness; however, propranolol was associated with a higher incidence of side effects and study withdrawals. In a second study, addition of propranolol to nitrendipine monotherapy produced a further decrease in blood pressure that was sustained over the year of study. These data suggest that nitrendipine provides additional effective and safe antihypertensive therapy, which can be used in place of or in combination with beta blockers.     

Alcohol-Induced Tolerance and Physical Dependence in Mice With Ethanol Insensitive α1 GABAA Receptors

Background: Although many people consume alcohol (ethanol), it remains unknown why some become addicted. Elucidating the molecular mechanisms of tolerance and physical dependence (withdrawal) may provide insight into alcohol addiction. While the exact molecular mechanisms of ethanol action are unclear, γ‐aminobutyric acid type A receptors (GABA_A‐Rs) have been extensively implicated in ethanol action. The α1 GABA_A‐R subunit is associated with tolerance and physical dependence, but its exact role remains unknown. In this report, we tested the hypothesis that α1‐GABA_A‐Rs mediate in part these effects of ethanol. Methods: Ethanol‐induced behavioral responses related to tolerance and physical dependence were investigated in knockin (KI) mice that have ethanol‐insensitive α1 GABA_A‐Rs and wildtype (WT) controls. Acute functional tolerance (AFT) was assessed using the stationary dowel and loss of righting reflex (LORR) assays. Chronic tolerance was assessed on the LORR, fixed speed rotarod, hypothermia, and radiant tail‐flick assays following 10 consecutive days of ethanol exposure. Withdrawal‐related hyperexcitability was assessed by handling‐induced convulsions following 3 cycles of ethanol vapor exposure/withdrawal. Immunoblots were used to assess α1 protein levels. Results: Compared with controls, KI mice displayed decreased AFT and chronic tolerance to ethanol‐induced motor ataxia, and also displayed heightened ethanol‐withdrawal hyperexcitability. No differences between WT and KI mice were seen in other ethanol‐induced behavioral measures. Following chronic exposure to ethanol, control mice displayed reductions in α1 protein levels, but KIs did not. Conclusions: We conclude that α1‐GABA_A‐Rs play a role in tolerance to ethanol‐induced motor ataxia and withdrawal‐related hyperexcitability. However, other aspects of behavioral tolerance and physical dependence do not rely on α1‐containing GABA_A‐Rs.     

Alterations of rat corticostriatal synaptic plasticity after chronic ethanol exposure and withdrawal

BACKGROUND: The purpose of this study was to investigate the effects of chronic ethanol exposure (CEE) and withdrawal on corticostriatal plasticity in rats. METHODS: We established an animal model of alcoholism using the method of Turchan et al. (1999). A synaptic model of long-term memory (long-term depression, LTD) was used as an index and the striatum, which is related to habit learning, was selected as a target region in the present study. The effects of CEE and withdrawal on the LTD were studied in striatal slices of ethanol-dependent rats using the extracellular recording method. RESULTS: A stable LTD can be induced after high-frequency stimulation (HFS) in the slices of control rats. Chronic ethanol exposure and withdrawal suppressed the induction of corticostriatal LTD to different extents, with the strongest suppressive effects on LTD occurring in the slices of rats exposed to ethanol for 10 days and in those withdrawn from ethanol for 1 day. Notably, 3 days of withdrawal resulted in the shift of corticostriatal synaptic plasticity from LTD to long-term potentiation, and the peak latencies of the population spikes were obviously shortened compared with those of control rats. After 7 days of withdrawal, ethanol's effects tended to disappear. CONCLUSIONS: These results suggest that the alterations of corticostriatal synaptic plasticity produced by CEE and withdrawal may play a prominent role in alcohol abuse and alcoholism.     

Comparison and additivity of nitrendipine and hydrochlorothiazide in systemic hypertension

Calcium channel blockers are highly effective antihypertensive agents and provide a good alternative to other medications used as initial or monotherapy. Although the calcium channel blockers act as peripheral vasodilators, they are unique among this group of drugs in lowering blood pressure in a sustained manner; several compensatory mechanisms are inhibited by virtue of either direct or indirect effects of these agents. In recent years, hypertension has generally been treated with a step-care approach, the limitations of which are now becoming apparent. Today, 4 classes of agents are effective and well tolerated as single therapy and might therefore be considered as first-line drug therapy: diuretics, beta blockers, converting enzyme inhibitors and calcium channel blockers. Preliminary results from an ongoing double-blind randomized trial comparing nitrendipine (a calcium channel blocker) and hydrochlorothiazide (a diuretic) in mild to moderate hypertension will be presented. Results from 63 patients showed the 2 agents to be equivalent in antihypertensive effects and in frequency of adverse reactions. Other data indicate that when nitrendipine and hydrochlorothiazide were combined, a further decrease in blood pressure was observed. Patient characteristics affecting drug choice and clinical situations in which calcium channel blockers can be used most effectively can now often be delineated.     

Individual differences in ethanol self-administration following withdrawal are associated with asymmetric changes in dopamine and serotonin in the medial prefrontal cortex and amygdala

BACKGROUND: Ethanol withdrawal alters brain neurochemistry, causes asymmetric activation of neurons in the medial prefrontal cortex (mPFC) and amygdala (AMY), and increases ethanol craving and drinking. Rats with intrinsic rightward-turning preferences drink more ethanol than those with left or no preferences; they also exhibit an ethanol-induced neurochemical activation that favors the right side of the mPFC. Our experiments used rats with different turning preferences to assess differences in withdrawal effects on mPFC and AMY neurochemistry as well as ethanol self-administration. METHODS AND RESULTS: Rats with left-turning, right-turning, and nonturning preferences were fed a 6% ethanol-containing liquid diet (WD) or a pair-fed control diet for 14 days. Differences in dopamine (DA), serotonin (5HT), norepinephrine (NE), and metabolite [3,4-dihydroxphenylacetic acid, homovanillic acid (HVA), and 5-hydroxyindoleacetic acid) concentrations were assessed in each side of the mPFC and AMY during acute withdrawal. Similar groups were fed the same diets and tested for consumption of 10% ethanol versus water and 1% sucrose versus water. WD increased HVA/DA in the mPFC and caused depletions of DA and 5HT in the mPFC and 5HT in the AMY. These effects were greater in the right than in the left side of these structures in rats with right-turning preferences. WD reduced ethanol drinking but right turners drank significantly more than left turners on day 2 of testing and drank more on days 2 and 3 than on day 1. No effects were observed on sucrose drinking. Similar groups were also trained to self-administer ethanol using a sucrose-fade sipper tube procedure that separated measures of ethanol seeking (bar pressing) and consumption. Following 14 days of vapor chamber exposure to ethanol, rats of all turning preferences had a lower rate of bar pressing on the first postwithdrawal day and shorter latencies to begin bar pressing on the third withdrawal day versus prewithdrawal baseline. Only right-turning-preference rats consumed more ethanol following withdrawal. CONCLUSIONS: These studies show that individual rats differ in postwithdrawal brain neurochemistry and ethanol consumption and that these differences are associated with differences in functional brain asymmetry.     

Inhibition of spontaneous and opiate-modified nociception by an endogenous neuropeptide with Phe-Met-Arg-Phe-NH2-like immunoreactivity.

In rats the antinociceptive actions of morphine (injected intraventricularly) or of [Met5]enkephalin-Arg6-Phe7 (YGGFMRF) (injected intrathecally) were attenuated by a pretreatment with 10 microliter of artificial cerebral spinal fluid containing 1 microM captopril/1 microM bestatin/2.5 microM Phe-Met-Arg-Phe-NH2 (FMRF-NH2) given 5 min earlier by the same route. A high molecular weight form of FMRF-NH2 purified from bovine brain attenuated the antinociceptive action of YGGFMRF. IgG, prepared from a specific FMRF-NH2 antiserum, elicited a moderate antinociception reversible by naloxone; in contrast, IgG prepared from control serum failed to change tail-flick latencies. In rats receiving morphine every 2 hr and anti-FMRF-NH2 IgG every 4 hr, the antinociceptive action was still evident after eight successive injections; in rats receiving only morphine, the antinociceptive action had disappeared after six successive injections. Morphine (1 microM) added to the perfusion fluid of the subarachnoidal spaces of rat spinal cord releases FMRF-NH2-like peptides in the perfusate.     

Effects of selective opioid receptor antagonists on alcohol-induced and nicotine-induced antinociception

BACKGROUND: Despite synergistic increases in risks of various cancers, the incidence of concomitant smoking and drinking remains high. An additive or synergistic analgesic effect of combined alcohol and nicotine may contribute to their coabuse. Recently, we provided evidence that doses of alcohol and nicotine that are ineffective in inducing an antinociceptive effect alone, when combined, can induce such an effect. Moreover, this antinociceptive effect could be attenuated by pretreatment with the nonselective opioid antagonist naloxone. The purpose of this study was to determine the role of selective opioid receptor subtypes (micro, delta, and kappa) in mediating the antinociceptive effects of alcohol, nicotine, and their combination. METHODS: Adult male Wistar rats were administered selective opioid antagonists, D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH(2) (CTAP, for micro receptor, 1.0 mg/kg), naltrindole (for delta receptors, 10 mg/kg), and norbinaltorphimine (nor-BNI, for kappa receptor, 10 mg/kg) before injection of alcohol, nicotine or their combination. The animals were tested in hot-plate and tail-flick assays, representing nociception mediated predominantly via brain or spinal pathways, respectively. All the injections were administered acutely and the nociceptive tests were carried out 20 minutes after alcohol and 10 minutes after nicotine administration. RESULTS: In general, the antagonists were more effective in blocking the effects of alcohol, nicotine, or their combination in the tail-flick versus the hot-plate assay. CTAP was most effective in blocking the effects of alcohol alone and nicotine alone in the tail-flick test, whereas in the hot-plate test both CTAP and naltrindole were more effective than nor-BNI. All 3 antagonists had a very similar profile in attenuating the combination of alcohol and nicotine effect in the hot-plate assay. None of the antagonists had a significant effect against the highest alcohol-nicotine dose in this test. In the tail-flick test, however, CTAP and naltrindole were more effective than nor-BNI in attenuating the highest alcohol-nicotine dose. CONCLUSIONS: The data suggest the utility of all 3 opioid antagonists in blocking the effects of alcohol, nicotine, or their combination in spinally mediated antinociception. Although the supraspinally mediated antinociception was also attenuated by the opioid antagonists, further investigation of combination doses of these antagonists in fully blocking the supraspinal effects or attenuating voluntary alcohol and nicotine intake is warranted.     

Effect of Voltage-Dependent Calcium Channel Blockers on Ethanol-Induced β-Endorphin Release From Hypothalamic Neurons in Primary Cultures

The voltage-dependent calcium channel (VDCC) has been shown to mediate calcium entry into neurons that regulates neurotransmission in many neuronal cells. Four major types of VDCCs (three high-voltage-activated L-, N-, and P-types and one low-voltage-activated T-type) have been identified in neurons. Involvement of the VDCC in ethanol-stimulated beta-endorphin (beta-EP) release from hypothalamic neurons has not been studied. In the present study, the role of VDCC on basal and ethanol-induced beta-EP release was determined by using rat fetal hypothalamic cells in primary cultures. Treatments with a 50 mM dose of ethanol for 3 hr increased immunoreactive beta-EP (IR-beta-EP) release from hypothalamic cells maintained in cultures for 9 days. Ethanol-induced IR-beta-EP release was inhibited by a P/Q-type channel blocker omega-agatoxin TK (0.1-1 microM), an N-type channel blocker omega-conotoxin (0.1-1 microM), an L-type blocker nifedipine (1-10 microM), and a T-type blocker flunarizine (1-10 microM). The minimal effective doses of these blockers that blocked the ethanol response produced no significant effects on basal release of IR-beta-EP; neither did these doses of the blockers produce any significant effects on cell viability. These results suggest that ethanol-stimulated IR-beta-EP release is regulated by extracellular calcium involving P-, N-, L- and T-type channels.     

Chronic, but not acute, nicotine exposure attenuates ethanol withdrawal-induced hippocampal damage in vitro

BACKGROUND: Long-term ethanol use and long-term tobacco use frequently occur together, which suggests concurrent dependence on ethanol and nicotine. Consequences of this form of polydrug dependence are not well understood, however. Previous evidence suggests detrimental effects of long-term ethanol and beneficial effects of nicotine exposure on neuronal viability. Thus, the present study was designed to use an organotypic hippocampal slice culture model to examine the ability of chronic and acute nicotine exposure to reduce neurotoxicity associated with withdrawal from long-term ethanol exposure. METHODS AND RESULTS: Twenty-four hours of withdrawal after continuous 10 day ethanol exposure (50 or 100 mM in culture medium) resulted in cytotoxicity in hippocampal slice explants obtained from neonatal rat, most notably in pyramidal cell layers of the CA1 region. Exposure of slices to the N-methyl-D-aspartate receptor blocker MK-801 during ethanol withdrawal significantly reduced this toxicity. Exposure of slices to nicotine (0.1-10.0 microM) during the 24 hr withdrawal period did not reduce hippocampal damage. However, treatment of slices with nicotine (0.1-10.0 microM) during 10 days of ethanol exposure was associated with significant reductions in subsequent withdrawal-induced cytotoxicity, an effect reduced by mecamylamine coexposure with nicotine and ethanol. CONCLUSIONS: These findings indicate the development of marked hippocampal neurotoxicity during withdrawal from long-term ethanol exposure that is mediated, in part, by overactivation of N-methyl-D-aspartate receptors. Furthermore, these data suggest that one consequence of concurrent dependence on ethanol and nicotine may be reduced neurological damage associated with ethanol withdrawal.     

Chronic Cadmium Exposure Attenuates Ethanol-Induced Hypoalgesia in the Adult Rat

Adult male rats were exposed to a diet containing either 100 ppm added cadmium (Cadmium-Diet), or a control diet containing no added chemicals (Control-Diet) for 67 days prior to pain reactivity testing using a tail-flick procedure. Rats were placed in restraining tubes for a 20-min acclimation period, then baseline tail-flick latencies in response to a radiant heat source were measured. Subsequently, half the animals from each group were serially injected intraperitoneally with either 0.5, 1.0, 1.5, or 2.0 g/kg body weight of a 20% v/v ethanol solution, and the other half of the animals were injected with an equivalent volume of saline. Tail-flick latencies were reassessed at 20-min intervals over the next 2 hr. Results indicated dose-dependent ethanol-induced hypoalgesia in the Control-Diet animals for the two highest doses, but ethanol-induced hypoalgesia was evident only at the highest dose for the Cadmium-Diet animals. Further, the magnitude of this hypoaigesic effect was significantly lower for the Cadmium-Diet animals than the Control-Diet animals at the 2.0 g/kg dose. Results are discussed in terms of an attenuation of the pharmacological properties of ethanol by cadmium.     

Effects of Chronic Ethanol Exposure on Oral Self-Administration of Ethanol or Saccharin by Wistar Rats

The study of alcohol abuse traditionally has placed great emphasis on the development of tolerance and dependence as key factors. However, animal models of ethanol self-administration in dependent rats have been difficult to establish, caused in part by ethanol's aversive taste cues and subsequent aversive effects (i.e., “hangover” malaise) that prevent substantial ethanol consumption. In this study, this problem was addressed in animals trained to self-administer ethanol (10% w/v) in a sweetened-solution fading procedure before induction of dependence and repeated exposure to withdrawal. Once stable rates of responding for ethanol were achieved, a palatable liquid diet containing 8.7% (v/v) ethanol was introduced as the sole source of calories and fluid for one group of rats [ethanol diet (ED) group]. A second group of rats received a control diet with sucrose isocalorically substituted for ethanol (CD group). After 14–17 days of liquid diet exposure, the rats were withdrawn once a week for 4 weeks and 8 hr into each withdrawal session were allowed to self-administer ethanol or water for 60 min. As compared with CD rats, ED rats showed significantly greater intake of ethanol, but not water. No significant differences were found when separate groups of ED/CD rats were allowed to self-administer an alternate reinforcer (0.0075% saccharin solution). Rats who consistently had blood alcohol levels (BALs) above 100 mg% at the time of withdrawal sustained high levels of ethanol self-administration throughout the four withdrawal sessions. In contrast, rats who had an average BAL at withdrawal below 100 mg% showed progressive decreases in ethanol self-administration during repeated withdrawal episodes. The results demonstrated that chronic exposure to ethanol and repeated periods of abstinence are accompanied by elevated rates of ethanol intake in certain animals, and the persistence of elevated self-administration behavior of individual rats is predicted by their BAL at the time of withdrawal.     

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.     

Corticosterone increases damage and cytosolic calcium accumulation associated with ethanol withdrawal in rat hippocampal slice cultures

BACKGROUND: Evidence suggests that stress hormones (i.e., glucocorticoids) may be increased during acute or chronic consumption of ethanol and during withdrawal from ethanol consumption, effects that may contribute to the development of cognitive impairment. The goal of the current studies was to examine the hypothesis that increased glucocorticoid levels in conjunction with ethanol exposure and withdrawal may cause hippocampal damage. METHODS: Organotypic hippocampal slice cultures were exposed to 50 mM ethanol for 10 days and withdrawn for 1 day. After withdrawal, cytotoxicity and cytosolic Ca2+ accumulation were measured using the nucleic acid stain propidium iodide and Calcium Orange, AM, respectively. Cultures were also treated with nontoxic concentrations of corticosterone (0.001-1 microM) during ethanol exposure and withdrawal or only during withdrawal. Additional cultures were coexposed to corticosterone and RU486 (0.1-10.0 microM), spironolactone (0.1-10.0 microM), or MK-801 (20 microM) during ethanol exposure and/or withdrawal. RESULTS: Ethanol withdrawal did not increase propidium iodide fluorescence and cytosolic Ca2+ levels. However, significant increases in propidium iodide fluorescence and in cytosolic Ca2+ accumulation were observed in cultures when corticosterone (> or = 100 nM) was exposed during ethanol treatment and/or withdrawal. These effects of corticosterone on ethanol withdrawal were attenuated by RU486 and MK-801 but not by spironolactone coexposure. CONCLUSIONS: This report demonstrated that corticosterone exposure during ethanol treatment and/or withdrawal resulted in significant hippocampal damage, possibly via activation of glucocorticoid receptors and enhancement of the glutamatergic cascade. The findings from these studies suggest that glucocorticoids contribute to the neuropathological consequences of alcohol dependence in humans.     

Influence of early-life adversity on responses to acute and chronic ethanol in female mice

Background

Stressful early-life experiences increase the risk of developing an alcohol use disorder. We previously found that male C57BL/6J mice reared under limited bedding and nesting (LBN) conditions, a model of early-life adversity, escalate their ethanol intake in limited-access two-bottle choice (2BC) sessions faster than control (CTL)-reared counterparts when exposed to chronic intermittent ethanol (CIE) vapor inhalation. However, the alcohol consumption of female littermates was not affected by LBN or CIE. In the present study, we sought to determine whether this phenotype reflected a general insensitivity of female mice to the influence of early-life stress on alcohol responses.

Methods

In a first experiment, CTL and LBN females with a history of 2BC combined or not with CIE were tested in affective and nociceptive assays during withdrawal. In a second group of CTL and LBN females, we examined ethanol-induced antinociception, sedation, plasma clearance, and c-Fos induction.

Results

In females withdrawn from chronic 2BC, CIE increased digging, reduced grooming, and increased immobility in the tail suspension test regardless of early-life history. In contrast, LBN rearing lowered mechanical nociceptive thresholds regardless of CIE exposure. In females acutely treated with ethanol, LBN rearing facilitated antinociception and delayed the onset of sedation without influencing ethanol clearance rate or c-Fos induction in the paraventricular nucleus of the hypothalamus, paraventricular nucleus of the thalamus, central nucleus of the amygdala, or auditory cortex.

Conclusion

CIE withdrawal produced multiple indices of negative affect in C57BL/6J females, suggesting that their motivation to consume alcohol may differ from air-exposed counterparts despite equivalent intake. Contrasted with our previous findings in males, LBN-induced mechanical hyperalgesia in chronic alcohol drinkers was specific to females. Lower nociceptive thresholds combined with increased sensitivity to the acute antinociceptive effect of ethanol may contribute to reinforcing ethanol consumption in LBN females but are not sufficient to increase their intake.     

Clinical L-type Ca(2+) channel blockade prevents ischemic preconditioning of human myocardium

Although Ca(2+) channel blockers are commonly used to control both blood pressure and angina in patients with coronary artery disease, clinical trials have associated the use of L-type Ca(2+) channel blockers with increased cardiovascular mortality. Recent evidence has implicated Ca(2+) entry through the L-type Ca(2+) channel during transient ischemia as a proximal stimulus for ischemic preconditioning (IPC) in experimental animals. We therefore hypothesized that clinical L-type Ca(2+) channel blockade prevents IPC in human myocardium. Human atrial trabeculae were suspended in organ baths, field simulated at 1 Hz, and force development was recorded. Following 90 min equilibration, trabeculae from control patients and patients taking L-type Ca(2+) channel blockers were subjected to simulated ischemia/reperfusion (I/R: 45/120 min) with or without 5 min of simulated ischemia (IPC stimulus) prior to I/R. IPC increased post-ischemic developed force in control patients from 14.6+/-2.6 to 43.1+/-3.5% baseline developed force (%BDF P<0.05 I/R vs IPC). Whereas IPC failed to increase post-ischemic developed force in myocardium from patients taking L-type Ca(2+) channel blockers (15. 1+/-1.9 vs 16.6+/-1.7 %BDF, P>0.05 L-type I/R v L-type IPC). We conclude that: (1) atrial muscle can be preconditioned by transient ischemia; (2) atrial muscle from patients taking L-type Ca(2+) channel blockers cannot be preconditioned by transient ischemia; and (3) the increased cardiovascular mortality historically associated with the use of Ca(2) channel blockers in patients with coronary artery disease may be, in part, due to the pharmacological inhibition of ischemic preconditioning.     

The decreased cellular expression of neuropeptide Y protein in rat brain structures during ethanol withdrawal after chronic ethanol exposure

Background: Neuropeptide Y (NPY) has been implicated in the alcohol-drinking behaviors of rodents. This study investigated the possible involvement of NPY in the neuroadaptational mechanisms to chronic ethanol exposure and its withdrawal.
Methods: Male Sprague-Dawley rats were treated either with Lieber-DeCarli ethanol diet or control diet for 15 days, and ethanol-fed rats were withdrawn for 0 and 24 hr. The protein expression of NPY was determined in cortical, hippocampal, amygdaloid, striatal, and hypothalamic structures by using the gold-immunolabeling histochemical procedure.
Results: It was found that ethanol withdrawal, but not ethanol treatment, produced significant reductions in NPY protein levels in (1) layers IV and V of the frontal and parietal cortex, (2) layer II of the piriform cortex, (3) the central and medial nuclei of the amygdala, and (4) the paraventricular nucleus of the hypothalamus in rat brain. Chronic ethanol exposure and its withdrawal had no effect on the NPY protein levels in layers II, III, and VI of the frontal and parietal cortex or cingulate gyrus, in hippocampal (CA1, CA2, CA3, and dentate gyrus) and striatal (caudate putamen and globus pallidus) structures, or in the ventro-medial hypothalamus and basolateral amygdala. However, chronic ethanol exposure and its withdrawal produced significant reductions in NPY protein levels in the arcuate nucleus of the hypothalamus and in layers IV and V of the cingulate gyrus.
Conclusions: These results suggest that the decreased protein levels of NPY in the central and medial nuclei of the amygdala, as well as in the cortical and hypothalamic structures, during ethanol withdrawal may play an important role in the neuromechanisms of some ethanol withdrawal symptoms.