Chronic daily ethanol and withdrawal: 1. Long-term changes in the hypothalamo-pituitary-adrenal axis

BACKGROUND: Hypothalamo-pituitary-adrenal (HPA) function has been demonstrated to be compromised for weeks and even months after alcoholics cease ethanol consumption. Because nonalcoholic subjects with family history-associated increased risk for alcoholism also exhibit compromised HPA function, it is not clear whether defects in the HPA axis of abstinent alcoholics reflect a preexisting condition that may be responsible for increased risk for alcohol abuse versus a persisting adaptational change in response to prolonged alcohol abuse. Consequently, we investigated whether chronic daily ethanol consumption and withdrawal by male Sprague Dawley rats would induce persistent HPA changes consistent with those demonstrated in abstinent alcoholics. METHODS AND RESULTS: In an initial experiment in which ethanol (5%, w/v) was incrementally introduced to liquid diet over a 1 week period followed by 4 weeks of chronic ethanol consumption, not only ethanol-treated rats but also pair-fed control rats exhibited decreased (p < 0.05 vs. ad-libitum-fed controls) anterior pituitary pro-opiomelanocortin (POMC) mRNA concentrations and associated decreases in plasma corticosterone and adrenocorticotropin (ACTH) levels for at least 3 weeks after gradual withdrawal of ethanol from the diet. Pair-feeding-induced decreases (p < 0.05) in thymus and spleen weights suggested that the pair-fed controls were likely stressed in this model, probably in response to the marked and irregular suppression of liquid diet consumption immediately after introduction of ethanol. Consequently, a second model was developed in which ethanol was introduced to the liquid diet much more gradually (i.e., over 3 weeks). In contrast with the rapid ethanol-introduction model, this more prolonged ethanol introduction followed by 4 weeks of chronic daily ethanol consumption increased plasma corticosterone levels (p < 0.05), increased adrenal gland weight (p < 0.05), and decreased thymus and spleen weights (both p < 0.01) without altering any of these parameters in the pair-fed controls. Three weeks after gradual withdrawal of ethanol from the diet, anterior pituitary POMC mRNA concentrations were suppressed (p < 0.05) and thymus and spleen weights were increased (p < 0.05) versus both pair-fed and ad-libitum-fed controls, accompanied by trends for decreased basal plasma corticosterone and adrenal weights. CONCLUSIONS: Chronic daily ethanol treatment induced changes in the HPA axis that persisted for at least 3 weeks after complete cessation of ethanol consumption. These persistent alterations in the HPA axis are similar to the aberrant HPA regulation of abstinent alcoholics, sons of alcoholics, Lewis rats, and individuals who suffer from posttraumatic stress disorder and some types of depression, that is, categories of individuals who all exhibit increased risk for high ethanol consumption. Thus, these chronic daily ethanol-induced persistent changes in the HPA axis may have significant roles in alcohol abstinence syndrome and may increase vulnerability to relapse.     

Increased ethanol self-administration and anxiety-like behavior during acute ethanol withdrawal and protracted abstinence: regulation by corticotropin-releasing factor

BACKGROUND: Animal models of alcohol dependence suggest that long-term alterations in brain corticotropin-releasing factor (CRF) systems, key mediators of the behavioral stress response, may be involved in the development and reinstatement of dependence on drugs of abuse. The objective of the present study was to investigate the role of CRF in the regulation of ethanol self-administration and to examine the behavioral stress response during acute withdrawal and protracted abstinence. METHODS: Male Wistar rats were made dependent on ethanol via chronic exposure to ethanol vapor. Ethanol self-administration and exploratory behavior in the elevated plus maze were measured at 2 hr and 3 to 5 weeks after exposure. The role of CRF in ethanol self-administration was examined via central injection of the CRF receptor antagonist D-Phe-CRF(12-41). RESULTS: Rats showed increased responding for ethanol 2 hr and 3 to 5 weeks after chronic ethanol exposure, which was attenuated by central injection of D-Phe-CRF(12-41). In addition, rats displayed a decrease in open-arm exploration in the elevated plus maze when tested 2 hr and 4 weeks after exposure. CONCLUSIONS: These results indicate that chronic ethanol exposure leads to increased ethanol self-administration and decreased open-arm exploration in the elevated plus maze during acute withdrawal and protracted abstinence. Attenuation of ethanol self-administration via central injection of D-Phe-CRF(12-41) implicates CRF as an underlying mechanism regulating long-term motivational effects associated with alcohol dependence.     

Chronic daily ethanol and withdrawal: 3. Forebrain pro-opiomelanocortin gene expression and implications for dependence, relapse, and deprivation effect

BACKGROUND: Although forebrain pro-opiomelanocortin (POMC)-producing neurons seem to mediate or modulate many responses to ethanol consumption, changes in activity of this opiomelanocortinergic system in response to chronic ethanol consumption, withdrawal, and subsequent abstinence remain unresolved. METHODS: We investigated the effects of chronic daily ethanol consumption, withdrawal, and subsequent abstinence on adult male Sprague-Dawley rat forebrain opiomelanocortinergic activity as reflected by changes in hypothalamic POMC messenger RNA (mRNA) content by using a well characterized liquid diet model that we have previously demonstrated to accurately simulate not only daily oral ethanol consumption quantity and pattern, but also both neuroendocrine and behavioral changes characteristic of actively drinking and subsequently abstinent alcoholics. RESULTS: After 7 weeks of daily ethanol consumption at night and withdrawal during the day, evening mediobasal hypothalamus POMC mRNA concentrations were suppressed versus both ad libitum-fed and pair-fed controls. Morning POMC mRNA concentrations were also suppressed versus ad libitum-fed controls and tended to be decreased versus pair-fed controls. Three weeks after gradual removal of ethanol from the diet, mediobasal hypothalamus POMC mRNA concentrations were increased relative to ad libitum-fed and pair-fed controls. Plasma concentrations of corticosterone, testosterone, and leptin were also altered by the daily ethanol/withdrawal treatment and by subsequent abstinence. CONCLUSIONS: Because each of these hormones has been demonstrated to modify forebrain POMC gene expression under some conditions, the overall changes in forebrain opiomelanocortinergic regulation in response to chronic daily ethanol/withdrawal and subsequent abstinence probably reflect, at least in part, regulation by multiple endocrine mechanisms, together with responses to stress, development of tolerance during chronic daily ethanol consumption, and rebound of function after termination of this consumption. Overall, the demonstrated changes in forebrain POMC gene expression are consistent with significant roles for forebrain opiomelanocortinergic regulation in mediating alcohol dependence, propensity to relapse, and the alcohol deprivation effect.     

Dose- and time-dependent expression of anxiety-like behavior in the elevated plus-maze during withdrawal from acute and repeated intermittent ethanol intoxication in rats

BACKGROUND: Withdrawal from acute bolus intraperitoneal (IP) injection of high doses of ethanol elicits anxiety-like behavior (e.g. Doremus et al., 2003; Gauvin et al., 1989, 1992) and conditioned place aversion (Morse et al., 2000). More recently we demonstrated that withdrawal from a single moderate dose of ethanol (2.0 g/kg) is accompanied by elevations in brain reward thresholds, and that repeated intermittent treatment with this dose results in a significant potentiation of reward deficit (Schulteis and Liu, 2006). METHODS: In the current study, the time- and dose-dependent emergence of anxiety-like behavior was measured in the elevated plus-maze at various times (3 to 24 hours) after acute or 3 daily IP injections of ethanol (1.0, 2.0, or 3.0 g/kg). Rats receiving daily handling for 2 days, and a single anxiety opportunity to explore the maze on a third day were divided into 1 of several treatment protocols: (1) NAIVE conditions: vehicle IP on all 3 days; (2) ACUTE conditions: vehicle on the first 2 days, ethanol on the third day; or (3) REPEAT conditions: ethanol on all 3 days. RESULTS: ACUTE ethanol elicited reduced exploration of the open arms of the elevated plus-maze in a dose- and time-dependent fashion: 1.0 g/kg failed to elicit any significant effects, whereas 2.0 and 3.0 g/kg ethanol elicited a significant anxiety-like response at 6 hours and 9 to 12 hours postinjection, respectively. REPEAT treatment was still without effect at any time point tested following 1.0 g/kg ethanol, but extended the time course of anxiety-like behavior after treatment with either 2.0 or 3.0 g/kg doses. REPEAT treatment with 2.0 and 3.0 g/kg ethanol also produced significant hypoactivity in the maze at some time points postinjection. CONCLUSIONS: Withdrawal from a single exposure to ethanol produces transient but significant anxiety-like behavior, and repeated intermittent bouts of intoxication result in a significant extension of the duration of effect. The rapid emergence and progression of negative emotional signs of withdrawal may be a significant factor in determining susceptibility to transition from casual drinking to loss of control and escalating patterns of consumption that result in alcoholism.     

Anxiety and sensitivity to ethanol and pentobarbital in alcohol withdrawal seizure-prone and withdrawal seizure-resistant mice

BACKGROUND: Withdrawal Seizure-Prone (WSP) and Withdrawal Seizure-Resistant (WSR) mice were selectively bred for high and low handling-induced convulsions, respectively, after chronic ethanol treatment. Withdrawal severity is one factor that may contribute to the development of alcoholism and/or substance abuse, and anxiety is another. We sought to explore whether these factors are genetically related. METHODS: WSP and WSR mice of two replicate pairs of selected lines were tested for anxiety-related behaviors on the canopy stretched-attend-posture apparatus 20 min after intraperitoneal injection of ethanol (2 g/kg, 20% v/v), pentobarbital (20 mg/kg), or an equivalent volume of saline. Dependent measures of anxiety included number of stretched attend postures (SAP) and time spent in the exposed area of the apparatus. Number of line crossings, which measures overall activity, was also scored. RESULTS: WSP mice given saline exhibited more SAP than WSR mice given saline, which indicated greater baseline anxiety. Ethanol and pentobarbital both reduced SAP and increased time spent in the exposed area of the apparatus, which indicated that both drugs exerted an anxiolytic effect. Despite baseline differences in SAP between selected lines, both anxiolytic drugs reduced SAP to similar levels in WSP and WSR mice. CONCLUSIONS: These results support the hypothesis that WSP mice are more sensitive than WSR mice to the anxiety-reducing effects of ethanol and pentobarbital. Some genes that influence this difference are likely to be the same as those that influence ethanol withdrawal severity. Thus, higher basal anxiety and greater genetic sensitivity to anxiolytic drug effects may relate to a greater genetic predisposition to the development of severe alcohol withdrawal signs.     

Induction of cyclooxygenase-2 in brain during acute and chronic ethanol treatment and ethanol withdrawal

Prostaglandins play an important role in the regulation of nervous system function including thermoregulation, autonomic nervous system function, hypothalamic regulation of pituitary function, and neuronal excitation. Prostaglandin synthesis is catalyzed by cyclooxygenase (COX; prostaglandin synthase) which occurs as two isozymes, COX-1 and COX-2. COX-1 and COX-2 are constitutively expressed in brain whereas COX-2 type is also inducible in brain by excitatory neurotransmission. Ethanol intoxication and the hyperexcitability of ethanol withdrawal may be influenced by inducible proteins, thus we investigated COX-2 in the rat brain during acute and chronic ethanol treatment, ethanol withdrawal, and after peripheral administration of excitatory amino acids. Kainic acid or NMDA treatment increased COX-2 immunoreactivity in the cortex, hippocampus, and amygdala. An acute dose of ethanol (5 g/kg, intragastric-i.g.) increased COX-2, particularly in the CA4 region of the hippocampus and agranular insular cortex. Chronic ethanol treatment (4 days-intragastric) robustly induced COX-2 in limbic cortex, isocortex, and amygdala. Particularly dense immunocytochemical staining was found in perirhinal and piriform cortices, dentate gyrus, and tenia tecta. During ethanol withdrawal, COX-2 expression increased further in some regions, peaking in most areas 16 hr after the last dose of ethanol. These results indicate that COX-2 immunoreactivity is: 1) increased in the brain during acute ethanol exposure that increases further during chronic treatment; 2) sensitive to excitatory amino acid receptor stimulation; and 3) dramatically increased during ethanol withdrawal. These studies suggest that COX-2 induction may be involved in the acute and chronic effects of ethanol.     

Chronic daily ethanol and withdrawal: 5. Diurnal effects on plasma thyroid hormone levels

We previously demonstrated that chronic daily ethanol consumption and daily withdrawal by male rats in a modified ethanol liquid diet paradigm produced (a) chronically increased adrenal glucocorticoid activity; (b) decreased plasma testosterone; (c) decreased forebrain proopiomelanocortin gene expression; and (d) corresponding alterations in plasma leptin levels—all of which are consistent with reported changes during alcohol abuse and alcoholism. Each of these systems interact with hypothalamo-pituitary-thyroid (HPT) regulation, and links between chronic alcohol abuse and thyroid dysfunction have been suggested by both human and rat studies. Accordingly, we have begun to investigate potential HPT mediation of, or response to, alterations in these systems by investigating plasma thyroid hormone levels in the same chronic daily ethanol/withdrawal paradigm. Chronic daily episodes of ethanol consumption and withdrawal by male Sprague-Dawley rats decreased plasma levels of free (non-protein-bound) triiodothyronine (T3) (p<0.01) and free thyroxine (T4) (p<0.05) in the morning but not in the afternoon, relative to both ad libitum-fed and pair-fed controls (n=9/treatment). Plasma total T4 levels were likewise suppressed (p<0.01) in the morning, whereas total T3 levels were increased (p<0.05) in the afternoon. These changes eliminated normal diurnal patterns (higher in the morning) of plasma free T3, free T4, and total T3 concentrations. Three weeks after cessation of ethanol consumption, morning plasma levels of free and total T3 and T4, as well as plasma thyroid-stimulating hormone (TSH), were all not significantly changed by the prior ethanol consumption or pair-feeding. These results reveal that plasma thyroid hormone concentrations are suppressed in a time of day dependent manner by chronic daily ethanol consumption and daily withdrawal in this model of chronic ethanol abuse. During subsequent long-term “abstinence,” these thyroid hormones returned to control levels. These results are consistent with evidence that thyroid function is commonly diminished in alcoholism, with variable reports of recovery during abstinence. Further investigations with this rat model of daily ethanol consumption and daily withdrawal will help resolve interactions and roles of the HPT axis in alcohol abuse.     

Evoked potential changes during ethanol withdrawal in rats.

We have recently observed an increase in central nervous system excitability during intoxication and alcohol withdrawal in alcoholics. Our present results demonstrate a similar phenomenon in rats. The hyper-excitability caused by ethanol withdrawal is still present subsequent to the overt behavioral symptoms of withdrawal.     

Effects of dexmedetomidine on rat locus coeruleus and ethanol withdrawal symptoms during intermittent ethanol exposure

In the present study, the neuroprotective effects of dexmedetomidine on rat locus coeruleus were studied during a 5-week intermittent ethanol exposure. Male Wistar rats (3 to 4 months old) were given ethanol or isocaloric sucrose by intragastric intubations three times a day for 4 days, which was followed by a 3-day withdrawal period. This 7-day cycle of ethanol exposure and withdrawal was repeated five times. Dexmedetomidine (at a dose decreasing from 30 microg/kg to 10 microg/kg, s.c.) was given to the treatment group during the withdrawal phase. The results showed that, during the 5-week experiment, dexmedetomidine significantly relieved the ethanol withdrawal syndrome, measured as the sum of the three most specific symptoms (rigidity, tremor, and irritability). The total neuron number of locus coeruleus (LC) decreased in the ethanol-treated group by 24%, compared with the nontreated control group and by 11%, compared with the sucrose-treated control group. Interestingly, the LC neuron numbers were found to decrease in the sucrose-intubated rats as well, compared with the nontreated control group. Dexmedetomidine was found to relieve ethanol-induced neuronal loss in the LC. Dexmedetomidine might be a new interesting alternative in the treatment of ethanol withdrawal syndrome, particularly due to its possible neuroprotective effects in the central nervous system.     

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.     

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.     

Comparison of the onset of hypoactivity and anxiety-like behavior during alcohol withdrawal in adolescent and adult rats

BACKGROUND: Early life alcohol use is associated with increased alcoholism risk. It has been suggested that alterations in the sensitivity of adolescents to the acute effects of ethanol may contribute to this risk by promoting excessive intake. However, an enhanced propensity for developing ethanol dependence or withdrawal-related behavior could also contribute to increased risk. The objective of these studies was to compare the appearance of ethanol withdrawal-related behaviors in adolescent and adult rats. METHODS: Male Sprague-Dawley rats were exposed to ethanol vapor (12 hr/day) for 12 or 14 days during adolescence or adulthood. In the first study, locomotor activity was assessed after 2, 4, 7, 10, and 14 days of ethanol exposure. In the second study, open field behavior was assessed after 5 or 12 days of ethanol exposure. In follow-up studies, changes in sucrose preference during ethanol withdrawal and motor activity during food restriction were assessed in adolescent rats. Withdrawal assessments were made 7 to 9 hr after daily exposure ended. RESULTS: Hypoactivity emerged rapidly in adolescent rats during ethanol withdrawal in activity tests, but comparable reductions were not found in adult rats. However, hypoactivity developed in both adolescents and adults in the novel open field. Enhanced anxiety-like behavior in the open field was not observed in either age group during withdrawal. Finally, sucrose preference was unchanged during ethanol withdrawal, and food restriction increased motor activity in adolescent rats. CONCLUSIONS: These data confirm that symptoms of withdrawal may be differentially expressed in adolescent and adult rats. However, discrepancies in hypoactivity between studies suggest that assessment in a novel versus familiar environment may influence the expression of withdrawal-related behaviors.     

EGF、SS在海洛因戒断、脱毒、复吸大鼠颌下腺组织中的表达

目的:研究表皮生长因子(epidermal growth factor,EGF)、生长抑素(somatostatin,SS)在海洛因戒断、脱毒及复吸大鼠颌下腺组织中表达的变化.方法:正常♂SD大鼠35只,随机分为正常对照组(NCG,n=5)、盐水对照组(SCG1、SCG2、SCG3,各组n=5)及实验组(n=5),实验...     

Effects of acamprosate on excitatory amino acids during multiple ethanol withdrawal periods

Background: Our previous studies on the effects of acamprosate on enhanced locomotion during repeated withdrawals are now extended to the effects of acamprosate on excitatory amino acids in the hippocampus during repeated ethanol withdrawals. Methods: In this study, Wistar rats were made ethanol dependent by 4 weeks of vapor inhalation. After this first cycle of chronic ethanol treatment, rats underwent repeated and alternate cycles of 24 hr withdrawals and 1 week of chronic ethanol treatment. The microdialysis technique was used together with high‐performance liquid chromatography and electrochemical detection to quantify different amino acids such as aspartate and glutamate. Results: An intraperitoneal administration of acamprosate (400 mg/kg) to naïve rats did not alter aspartate or glutamate levels compared with the saline groups. During the first cycle of ethanol withdrawal, the administration of acamprosate (400 mg/kg, intraperitoneally) 2 hr after the commencement of ethanol withdrawal decreased both aspartate and glutamate microdialysate levels when compared with their respective saline group. Acamprosate administration also significantly decreased glutamate levels during the third withdrawal compared with the saline group, whereas no changes were seen in aspartate levels. Conclusion: The results of this work demonstrate that acamprosate reduced the excitatory amino acid glutamate increase observed during repeated ethanol withdrawal. These effects of acamprosate may provide a protective mechanism against neurotoxicity by reducing excitatory amino acids, particularly glutamate.     

Cardiac and mood-related changes during short-term abstinence from crack cocaine: the identification of possible withdrawal phenomena.

Studies assessing withdrawal phenomenon during short-term abstinence from chronic cocaine use have been limited. Although cocaine abusers are reported to be at increased risk for cardiac disorders, little research has assessed cardiac parameters in cocaine abusers and subsequent changes in these parameters that may be associated with the discontinuation of cocaine use. In this study, we categorize 441 chronic cocaine abusers into three groups based on self-reported length of abstinence from cocaine use at entry into a trial approved by the National Institute on Drug Abuse (NIDA) assessing the use of pergolide mesylate in treating relapse and craving in crack cocaine abuse. Electrocardiogram (ECG) PR intervals were found to be correlated positively with length of abstinence, returning to normal population levels within 30 days. In addition, levels of generalized anxiety, nervousness, and heart racing were found to be correlated negatively with length of abstinence from crack cocaine. This work provides preliminary evidence of cardiac and mood-related parameters that are associated with cocaine abstinence and that may indicate specific withdrawal phenomena in chronic users. In addition, these results suggest that the risk of cardiomyopathies associated with abnormal atrial-ventricular polarization may dissipate relatively quickly in abusing individuals.     

Increased blood 8-hydroxy-2-deoxyguanosine levels in methamphetamine users during early abstinence

Background: Reactive oxygen species (ROS) are thought to play a role in the adverse physical and mental consequences of methamphetamine usage. The oxidative DNA adduct 8-hydroxy-2?-deoxyguanosine (8-OHdG) is a well-known biomarker of ROS-induced DNA damage. Currently, there is insufficient clinical information about methamphetamine-induced oxidative DNA damage. Objectives: This study examined differences in blood levels of 8-OHdG between methamphetamine users and non-users as well as alterations in 8-OHdG levels after 2 weeks of methamphetamine abstinence. Methods: We recruited 182 methamphetamine users (78.6% of male) and 71 healthy controls (95.8% of male). Baseline serum 8-OHdG levels were measured in both groups using a competitive enzyme-linked immunosorbent assay. In methamphetamine users, 8-OHdG levels were measured again 2 weeks after baseline measurement. Results: The results showed that methamphetamine users had significantly higher 8-OHdG levels (0.34 ± 0.13 ng/mL) than healthy controls (0.30 ± 0.08 ng/mL) (p < 0.001). The 8-OHdG levels did not alter after 2 weeks of methamphetamine abstinence (0.32 ± 0.12 ng/mL, p = 0.051 compared to baseline measurement; p = 0.12 compared to healthy controls). No significant correlations were observed between baseline 8-OHdG levels in methamphetamine users and post-abstinence interval, age of the first methamphetamine use, duration of methamphetamine use, or history of frequent methamphetamine use. Conclusion: Our findings suggest that methamphetamine users had an enhanced level of oxidative damage, which did not normalize during early abstinence. Future studies are required to determine the effects of long-term methamphetamine abstinence and potential confounders on 8-OHdG levels in methamphetamine users.     

Chronic daily ethanol and withdrawal: 4. Long-term changes in plasma testosterone regulation, but no effect on GnRH gene expression or plasma LH concentrations

Although ethanol has been repeatedly demonstrated to inhibit the hypothalamo-pituitary-testes axis by multiple mechanisms, plasma testosterone levels can be normal in alcoholics who do not exhibit severely compromised liver function and even increased in some abstinent alcoholics, suggesting that adaptive changes to chronic alcohol abuse may alter these regulatory mechanisms. To address this variability, we have investigated the effects of chronic ethanol and withdrawal on rat testosterone regulation using a well-characterized liquid diet model that we have previously demonstrated to (1) provide daily oral ethanol consumption that produces behaviorally relevant plasma ethanol levels during the active (awake) stage of the photoperiod; (2) establish physical dependence on ethanol; and (3) produce not only hypothalamo-pituitary-adrenal axis, but also behavioral (anxiety-like behavior, response to novelty, sucrose preference) changes consistent with those of actively drinking and subsequently abstinent alcoholics. The results demonstrate that chronic daily episodes of ethanol consumption and withdrawal by male Sprague-Dawley rats decreased (p<0.01) plasma testosterone levels late in the afternoon (by 70% relative to ad libitum-fed controls and 63% relative to pair-fed controls), but not in the morning. During gradual cessation of daily ethanol consumption, morning plasma testosterone levels increased, and this 90–115% (p<0.05) increase was maintained for 3 d after complete cessation of ethanol consumption. Three weeks after cessation of ethanol consumption, plasma testosterone levels were again increased by approx 100% (p<0.01). Plasma luteinizing hormone (LH) concentrations and anterior hypothalamus/preoptic area gonadotropin-releasing hormone (GnRH) mRNA levels were not altered at any of these time points. Thus, chronic daily ethanol consumption and daily withdrawal induced changes in circulating testosterone regulation that (a) were time of day dependent and (b) included adaptive changes persisting long after consumption of ethanol ceased. Accordingly, resolution of changes in testosterone regulation and their potential roles in alcohol abuse and relapse will require evaluating changes throughout the circadian cycle during, shortly after, and long after active alcohol abuse.     

Chronic continuous nicotine exposure during periadolescence does not increase ethanol intake during adulthood in rats

BACKGROUND: Nicotine has been considered as the gateway drug, because many teenagers experience cigarette smoking before seeking out other drugs. By using an animal model system, we assessed the effects of chronic continuous nicotine exposure during periadolescence on ethanol intake during young adulthood. METHODS: Periadolescent Sprague-Dawley rats (35 days old) were used at the beginning of this study. These animals received subcutaneous implantation of nicotine pellets (15 or 25 mg in 21-day time-release pellets) or placebo pellets (0 mg of nicotine) on postnatal day 35. Beginning on postnatal day 53, the animals received various concentrations of ethanol solution during their active period (5:00 PM to 9:00 AM) starting with 2% (v/v, 4 days), then 5% (5 days), 8% (6 days), and 10% (6 days). Between 9:00 AM and 5:00 PM of the same day, the ethanol solution was replaced by regular tap water. The amounts of ethanol solution and regular water were measured daily. RESULTS: The analyses showed that ethanol intake (grams per kilogram of body weight) in the nicotine 15 and 25 mg groups did not differ from that in the nicotine 0 mg group, and no sex difference was found in ethanol intake. However, ethanol intake was increased as a function of the treatment days. CONCLUSIONS: The results showed that chronic continuous nicotine exposure during adolescence did not increase ethanol intake in rats during young adulthood.