Tolerance to cannabinoid-induced behaviors in mice treated chronically with ethanol

Rationale  

Chronic ethanol (EtOH) treatment decreases the motor-impairing effects of cannabinoids and downregulates the cannabinoid type 1 (CB1) receptor. However, these studies have been limited to measures of ataxia and analysis of CB1 expression from whole-brain or hippocampal preparations.     

Effect of acute administration of ethanol on beta-endorphin plasma level in ethanol preferring and non-preferring rats chronically treated with naltrexone

An ample support can be found in professional literature for the hypothesis that the endogenous opioid system plays an important role in developing a craving for alcohol. It is well established that people with a genetic deficit of beta-endorphin are particularly susceptible to alcoholism. In our study, we looked into the beta-endorphin plasma level of animals with high- and low-risk of alcohol dependency after repeated treatment with naltrexone, the opioid antagonist known to be effective in the treatment of alcoholism. We used the Warsaw High Preferring (WHP) and Warsaw Low Preferring (WLP) rats and treated them for 10 days with naltrexone in a dose of 2 mg/kg i.p. One hour before blood collection the rats were injected with a single dose of ethanol. A prolonged naltrexone treatment or a single application of ethanol resulted in the increase of the beta-endorphin plasma level. In the WLP rats repeated naltrexone treatment prevents the ethanol-induced increase in beta-endorphin plasma level. In the WHP rats the level of this peptide was similar to it while they were undergoing the naltrexone treatment or had received a single alcohol injection. This finding supports the proposition that the endogenous opioid system plays an important role in developing a craving for alcohol. It is likely that effectiveness of naltrexone in reducing craving for alcohol results from the attenuation of the rewarding properties of ethanol and restoring the beta-endorphin deficit in reward system.     

Phencyclidine-induced head-twitch response in rats treated chronically with methysergide

This study was designed to assess whether phencyclidine (PCP)-induced behaviors in rats were potentiated after two days' withdrawal from chronic methysergide (a 5-HT2 receptor blocker) treatment (10 mg/kg per day i.p. for 12 days), in order to confirm the involvement of 5-hydroxytryptamine (5-HT) neurons in PCP actions. The PCP (10 mg/kg)-induced behaviors (head-twitch, head-weaving, turning and backpedalling) were attenuated by successive pretreatment with PCP (10 mg/kg per day i.p. for 12 days), while PCP- and 5-methoxy-N,N-dimethyltryptamine (2 mg/kg)-induced head-twitch increased significantly after the repeated methysergide treatment was stopped. The development of tolerance to PCP-induced head-twitch was antagonized by pretreatment with methysergide. Furthermore, Scatchard plots of specific [3H]ketanserin binding at the 5-HT2 receptors and [3H]PCP binding at the PCP receptors in the methysergide group revealed significant increases in binding capacity (Bmax) with no change in affinity (Kd). On the contrary, after development of tolerance to PCP, there were significant decreases in Bmax of [3H]ketanserin binding with no change in affinity. PCP can thus displace [3H]ketanserin at the 5-HT2 receptor site, but not [3H]5-HT at the 5-HT1 receptor site. These facts indicate that PCP may produce head-twitch via an agonistic interaction with 5-HT2 receptor sites.     

Serum lipid peroxides in rats treated chronically with adriamycin

Rats treated chronically with the anticancer agent adriamycin exhibited lipid peroxides in the serum and hyperlipidemia. Independent assay methods based on thiobarbituric acid reactivity and iodometric titration confirmed the presence of both lipid endoperoxides and hydroperoxides. Fractionation studies indicated that lipid peroxides were mainly associated with neutral lipids, including triglycerides, cholesterol esters and cholesterol, rather than with phospholipids. The lipid peroxides were distributed throughout the major serum lipoprotein classes. Although the origin of the lipid peroxides has not been established, the dose dependence for elevation of serum lipid peroxides approximately corresponds to that required for the development of cardiomyopathy. These findings support the conclusion that lipid peroxides are formed in vivo in rats treated chronically with adriamycin.     

Paroxetine alters KCl- or ATP-induced contractile responses of isolated vas deferens in rats chronically treated with ethanol.

Chronic ethanol administration affects many organ systems, including sexual organs. One of these organs is the vas deferens whose contractility can also be altered by selective serotonin re-uptake inhibitors (SSRIs). The aim of the present study, is to evaluate whether paroxetine (PX), a SSRI, can modify the contractile responses of isolated vas deferens obtained from rats chronically treated with ethanol to the contractile agents, potassium chloride (KCl) and adenosine triphosphate (ATP). For 21 days, alcohol was applied with a modified liquid diet to sexually mature male Sprague-Dawley rats (200-240 g). The vas deferens of the rats were excised at the end of day 21 and suspended in the organ baths by classical pharmacological methods. The responses to contractile agents tested were decreased by chronic ethanol treatment in all groups compared to their untreated matches. PX (10(-7) and 10(-6)M) potentiated the contractions to KCl (20-180 mM) and ATP (10(-6) to 10(-3)M) in epididymal portion but its higher concentrations (10(-5) and 10(-4)M) inhibited the responses, both in the control and chronically ethanol treated rat groups. Prazosin (PR), an alpha adrenergic receptor blocker, could not inhibit PX-induced potentiation in lower concentrations of KCl but could inhibit the potentiation occurred at higher concentrations of KCl in epididymal portion both in the control and chronically ethanol treated rat groups. PR also inhibited PX-induced potentiation on the responses to ATP in epididymal portion both in the control and chronically ethanol treated rat groups. In conclusion, all the results obtained in this study, suggest that chronic ethanol treatment decreased the contractility of vas deferens but did not alter the action pattern of PX on responses to KCl and ATP in rat vas deferens. On the other hand, the potentiation of responses to contractile agents induced by PX can be partially considered as the result of inhibition of noradrenaline re-uptake.     

Glucose homeostasis in rats treated acutely and chronically with quinine

Glucose homeostasis in normal rats was studied after chronic or acute administration of quinine. Male rats received a daily dose of 10-30 mg/kg of quinine in the drinking water for 20 weeks. The high dose caused a slight decrease in food intake and weight gain. Though basal plasma insulin levels were increased in treated rats, their plasma glucose levels were only slightly and not consistently decreased. After oral or intravenous administration of glucose, the plasma insulin levels were higher and the disappearance rate of glucose was greater in rats receiving quinine than in the controls. The insulin content of the pancreas was not affected by quinine treatment. Intraperitoneal injection of a high dose of quinine (30 mg/kg) transiently increased plasma glucose and insulin levels. The insulin response was increased during a subsequent administration of glucose but the glucose levels were not modified. This study shows that chronic administration of quinine increases plasma insulin levels, accelerates disposal of oral or intravenous glucose but does not cause hypoglycaemia in normal rats.     

Motility effects of methamphetamine in rats chronically treated with morphine

The dose/time effects of MAMPH were studied in naive rats and in rats previously treated daily with 20 mg/kg of morphine for 26 days. The animals were tested in jiggle-cage actographs for seven hours after MAMPH treatment. The data related to the motility scores were analysed as response surfaces by the analysis of variance. In addition the ED_{50 s} for the appearance of stereotyped behaviour were calculated for both groups of animals. It was found that the chronic morphine treatment altered neither the response surface of MAMPH effect upon activity nor the ED₅₀ values for the appearance of stereotyped behaviour. The data do not support the hypothesis of a dopamine receptor supersensitivity during chronic morphine treatment but rather suggest that pre-synaptic changes in dopamine turnover can take place when rats are treated repeatedly with opiates.     

The role of dopamine in the facilitatory effect of angiotensin II on impaired learning in rats chronically treated with ethanol

Rats with impaired active avoidance induced by chronic (9 weeks) administration of ethanol were studied. Angiotensin II (ANG II) administered (ICV, 2.0 g) 12 h after the withdrawal of the alcohol not only neutralized the toxic effect of ethanol but also improved learning. When administered on the 5th day after ethanol withdrawal, the effect of ANG II was weaker. Tests of stereotypy and catalepsy were used to study the possible role of the dopaminergic system in this action of ANG II. It was shown that both chronic alcohol treatment and ANG II alone increased apomorphine (1 mg/kg) and amphetamine (7.5 mg/kg) stereotypy but the effects of ANG II were greater. ANG II did not change the stereotypy induced by amphetamine but increased the stereotypy induced by apomorphine in the group of animals chronically treated with alcohol. Haloperidol — induced catalepsy was reduced in these rats. ANG II alone intensified catalepsy and eliminated the effect of ethanol. Both ANG II and alcohol increased striatal dopamine (DA) concentration. This effect of ANG II was significantly greater in the animals chronically treated with alcohol. The above changes were not observed after the DA level had been reduced by alpha-methyl-p-tyrosine (250 mg/kg), nor were changes observed in the striatal DOPAC. The results suggest involvement of the central dopaminergic system in the effect of ANG II on the ethanol — induced impairment of acquisition of active avoidance but, however, the results of the biochemical determinations of DA turnover do not provide an explanation of these changes.     

Effect of 6-n-propyl-2-thiouracil on the rate of ethanol metabolism in rats treated chronically with ethano

Chronic ethanol administration results in an increase in the ethanol metabolic rate (EMR), and this may be related to the production of alcoholic liver disease. Treatment with the antithyroid drug 6-n-propyl-2-thiouracil (PTU) for a 10-day period (20 mg·kg^?1·day^?1) reduced the EMR of chronically ethanol-treated rats, but had no effect on the EMR of control rats. This preferential inhibitory effect of PTU was observed either when PTU treatment was started after 20 days of ethanol consumption, or when ethanol and PTU administration were started at the same time. A single dose of PTU (20 mg/kg), given 1 hr before the experiment, had no effect on the EMR of rats treated chronically with ethanol, or on controls. Ten days of PTU treatment did not alter the hepatomegaly which had resulted from chronic ethanol treatment. These results are consistent with the hypothesis that thyroid hormones play a direct or permissive role in producing the increase in EMR seen after chronic ethanol treatment and are in agreement with an increased reoxidation of reducing equivalents in the liver of chronically ethanol-fed animals.     

Serotonin-mediated behavior in rats chronically treated with (-) deprenyl

(-) Deprenyl given in small (0.25 mg/kg) daily doses for 30 days to rats left the serotonin (5-HT) and the 5-hydroxyindoleacetic acid (5-HIAA) levels in the striatum unchanged. The postsynaptic 5-HT receptor responsiveness, as measured with 5-methoxy-N,N-dimethyl-tryptamine (5-MeODMT), remained also unaltered. In (-) deprenyl-treated rats the p-chloroamphetamine (PCA)-induced 5-HT syndrome was significantly increased and this enhancement of the PCA effect was not abolished by the reserpine-induced depletion of the 5-HT stores.     

Lipid peroxidation in isolated hepatocytes from rats ingesting ethanol chronically

Summary Isolated hepatocytes from rats consuming ethanol (8.5 g/kg) daily produce malondialdehyde in significantly higher amounts than liver cells from control animals. The release of LDH and the uptake of trypan blue in both types of hepatocytes do not differ during the incubation period of 2 h. GLDH, however, is only set free into the medium from liver cells of ethanol drinking rats, indicating that mitochondrial alterations are involved.Bomotrichloromethane (CBrCl₃) promotes lipid peroxidation in hepatocytes from ethanol drinking rats in a much higher degree than in cells from control rats. The cell damage induced by CBrCl₃ and indicated by a release of LDH and GLDH from the hepatocytes and their uptake of trypan blue is also much more pronounced in liver cells from ethanol drinking animals.The stronger action of CBrCl₃ cannot be explained by an enhanced microsomal metabolism, because no increase of drug metabolizing enzymes could be observed. The relatively low ethanol consumption did not influence body growth and liver weight and did not evoke any triglyceride accumulation.The normal balance between processes favouring lipid peroxidations and reactions protecting the liver cells seems to be shifted to a state during alcohol intake which promotes formation of radicals.     

Increased myocardial alpha 1 adrenoceptor density in rats chronically treated with propranolol

Chronic treatment with propranolol for 6 weeks resulted in a 16.6% increase, over the level in control rats, in myocardial alpha 1-adrenoceptor density as measured by [3H]prazosin binding. The apparent affinity remained unaffected. No changes were observed in beta-adrenoceptor density and apparent affinity as measured by [3H]dihydroalprenolol binding. It is concluded that myocardial alpha 1-adrenoceptors might have a compensatory role under conditions where beta-adrenergic effects are attenuated.     

乙醇作用下大鼠线粒体改变的定量分析

应用微机图像处理技术，对大鼠的肝和心肌细胞线粒体进行了形态学测量和文理结构分析。结果表明，对照组肝、心肌细胞线粒体的截面周长分别为３．７和４．０ｕｍ，截面面积分别为０．６９和０．８８ｕｍ＾２。在乙醇作用下，线粒体出现肿胀，截面面积平均增大８－１０％，同时线粒体的嵴变短和出现空化的数目成倍增加，并有一定的剂量效应关系。     

Hippocampus and locus coeruleus activity on rats chronically treated with diazepam

The neural mechanisms underlying benzodiazepine (BZD) dependence remain equivocal. The present studies tested the hypothesis that similar neural circuitry might be involved in the effects of chronic 7-chloro-1-methyl-5-phenyl-3H-1,4-benzodiazepine-2(1H)-one, diazepam (DZ, Roche), administration and withdrawal. The results of our study showed an increased hippocampal synaptic plasticity in slices from rats chronically treated with DZ (5 mg/kg/18 days), assessed as a decrease of the threshold in the stimulation rate for long-term potentiation (LTP) elicitation. Rats with the same schedule of DZ administration but without signs of withdrawal behaved similarly to vehicle-treated ones (VEH), in the threshold to induce LTP. Furthermore, the activity of locus coeruleus (LC) norepinephrine (NE) neurons in rats tested 24 h after the last DZ injection showed a significant increase. On the other hand, rats that after chronic DZ administration did not develop signs of withdrawal and exhibited a similar pattern of discharge on LC-NE nucleus compared with their controls. We conclude that chronic DZ administration enhances both hippocampal synaptic plasticity and activity of LC-NE neurons. This neural system could be the biological substrate underlying the behavioral alterations accompanying chronic DZ administration and withdrawal.     

Evaluation of tissue indicators of oxidative stress in rats treated chronically with adriamycin

Rats treated chronically with the anticancer agent adriamycin to a cumulative dose of 21 mg/kg, which was sufficient for development of an early stage of cardiomyopathy, were examined for evidence of lipid peroxidation and oxidative stress in vivo by several methods. Fluorometric analysis of lipid extracts suggested that fluorescent products of lipid peroxidation reactions were elevated about 3-fold in kidney, 40% in heart, and 10% in liver. However, lipid hydroperoxides and endoperoxides were not found to any significant extent in heart, liver or kidney. By contrast, as previously reported, the serum of adriamycin-treated rats showed substantial levels of lipid peroxide compounds. Measurements of glutathione levels indicated increases of about 50% in kidney and 20% in heart, and a decrease of 20% in liver, on a per gram tissue basis, after adriamycin treatment. Levels of protein-bound mixed disulfides were not altered after adriamycin treatment in heart, liver or kidney. Cardiac glutathione peroxidase activity was increased 30% after chronic adriamycin treatment, whereas glutathione reductase activity was unchanged. The results indicate that the major organs of rats treated chronically with adriamycin exhibit at least some persistent biochemical changes that are consistent with oxidative stress in vivo. The different types of lipid peroxidation products found in tissues as compared to serum may reflect, in part, the operation of membrane peroxidation repair processes.     

Modulation of the inflammatory response in rats chronically treated with the antidepressant agomelatine

Growing evidence suggests that the activation of the inflammatory/immune system contributes to depression pathogenesis, a hypothesis that might hold strong clinical implication. Indeed more than 30% of depressed patients fail to achieve remission, which poses the necessity to identify systems that may represent novel targets for medications. Accordingly, goal of this study was to evaluate the ability of the antidepressant agomelatine to modulate specific components of the immune response in the rat brain following an inflammatory challenge with lipopolysaccharide (LPS). To this aim, adult male rats were chronically treated with agomelatine before being acutely challenged with LPS 16 h after the last drug administration. Rats were sacrificed 2, 6, or 24 h after the challenge and several components of the inflammatory response have been investigated by using real-time PCR or ELISA. We found that agomelatine significantly reduced the LPS-induced up-regulation of the pro-inflammatory cytokines interleukin-1β and interleukin-6 in the rat brain as well as at peripheral level. At central level, these effects are associated to the inhibition of NF-κB translocation as well as to alterations of mechanisms responsible for microglia activation. In addition, we found that agomelatine was also able to alter the expression of enzymes related to the kynurenine pathway that are thought to represent important mediators to inflammation-related depression. These data disclose novel properties that may contribute to the therapeutic effect of agomelatine providing evidence for a crucial role of specific components of the immune/inflammatory system in the antidepressant response and thereby in depression etiopathology.     

The pharmacokinetics of phentermine and chlorphentermine in chronically treated rats

Young rats were treated with [³H]labelled phentermine or chlorphentermine for varying periods (1 day to 8 weeks). The plasma tissue and concentrations of the drugs were determined. The distribution of phentermine reflected a partition, the tissue: blood ratios remaining constant for the entire period. In contrast, chlorphentermine was increasingly accumulated the longer the treatment lasted, as indicated by rising tissue: blood ratios. Chlorphentermine proved to be tightly bound to tissue components. The highest tissue: blood ratio (160 after 8 weeks) was found in lungs and the highest increase in the accumulation rate (10 fold in 8 weeks) was for the adrenals. These results, together with biochemical and ultra-structural findings, suggest that the highly amphiphilic chlorphentermine induces an impairment of phospholipid metabolism resembling lipidosis.