Effects of antihistaminics on naloxone-induced withdrawal in morphine-dependent mice

Some histamine H1 (tripelennamine, diphenhydramine and cyclizine) and H2 (ranitidine and cimetidine) antagonists (1 and 10 mg/kg) were administered to morphine — dependent mice to evaluate the changes on naloxone-induced abstinence syndrome. When antihistaminics were administered 30 min before naloxone (1 mg/kg) on day 4 of morphine addiction, the two doses of the three H1 antagonists and the higher dose of ranitidine inhibited shaking behavior. Furthermore, the two doses of tripelennamine and the higher dose of diphenhydramine, cyclizine and cimetidine enhanced jumping behavior. When antihistaminics were administered chronically (during the 4 days of morphine addiction), tripelennamine, cyclizine and ranitidine (all at 10 mg/kg) inhibited shaking behavior. The three H1 antihistaminics used enhanced the number of jumps per mouse whereas ranitidine decreased this response. No significant changes were found in the rest of the withdrawal symptoms after the antihistaminics were administered. The participation of serotonergic and catecholaminergic mechanisms is discussed.     

Changes induced by sodium cromoglycate on brain serotonin turnover in morphine dependent and abstinent mice

This study was designed to explain the action of sodium cromoglycate (CRO) on the brain serotonergic system in control, morphine tolerant (by SC implantation of a 75 mg morphine pellet), and also in morphine dependent mice just before naloxone-precipitated withdrawal. After SC injections of CRO in control mice, morphine tolerant mice (day 4 of addiction), and 1 h before abstinence (withdrawal was induced by SC injection of 1 mg/kg naloxone on day 4 of addiction), animals were decapitated and various brain areas were rapidly removed. 5HT (Serotonin) and 5HIAA (5-hydroxyindole-3-acetic acid) were measured by high performance liquid chromatography coupled with electrochemical detection (HPLC-ECD). The ratio 5HIAA/5HT provided one index by which the turnover of the indoleamine was measured. CRO increased the turnover of 5HT in most of the brain areas studied in both control and morphine dependent mice. Furthermore, previous administration of CRO prior to naloxone challenge induced a significant increase in the 5HIAA/5HT ratio in the hypothalamus and striatum. These results are discussed as the reason for the preventive effect of CRO on jumping behaviour in morphine abstinent mice.     

Changes induced by sodium cromoglycate in brain catecholamine turnover in morphine dependent and abstinent mice

The effects of sodium cromoglycate (CRO) were studied in relation to the metabolism of brain catecholamines: dopamine (DA) and noradrenaline (NA), and their metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 4-hydroxy-3-methoxyphenylethyleneglycol (MHPG). CRO was injected SC in control mice, morphine-tolerant mice (tolerance was induced by SC implantation of a 75 mg morphine pellet; CRO was administered on day 4 of addiction) and 30 min before abstinence (withdrawal was induced by SC injection of naloxone (1 mg/kg) on day 4 of addiction). Brain catecholamines and their metabolites were measured using high performance liquid chromatography coupled with electrochemical detection (HPLC-ECD), for DA, NA, DOPAC and HVA, and coupled with fluorescence detection for MHPG. The ratios of DOPAC + HVA/DA and MHPG/NA were kept as an index of DA and NA turnovers, respectively. CRO administered 30 min before naloxone-precipitated withdrawal diminished significantly NA levels in frontal cortex. CRO increased DA turnover in striatum and frontal cortex in naive animals and significantly diminished DA levels in frontal cortex and DOPAC levels in frontal cortex and midbrain in morphine-dependent mice. These findings are discussed in relation to the protective effects of CRO on opiate withdrawal and the effects of CRO on locomotor activity.This work was supported by a grant from the Fondo de Investigaciones Sanitarias de la Seguridad Social (FIS, programme no. 0166/93).     

Effect of morphine on the brain histamine levels in stress-exposed rats

The effect of morphine on brain histamine levels in stress-exposed rats was investigated. It seemed that the brain histamine level was not directly affected by stressors. However, morphine induced a sharp rise in the brain histamine levels in both morphine-treated and morphine-treated stressed groups. This effect of morphine was reversed by naloxone.     

Effects of trepelennamine on brain monoamine turnover in morphine dependent and abstinent mice

Previous studies have reported that the histamine H₁ receptor blocker tripelennamine potentiates morphine withdrawal. In this paper, the in vivo effects produced by tripelennamine on the turnover of serotonin (5-HT), dopamine (DA) and noradrenaline (NA) in the whole brain, excluding the cerebellum, were studied in control, morphine-dependent (by SC implantation of a 75 mg morphine pellet) and morphine-dependent male CD1 mice just before naloxone-precipitated withdrawal. Tripelennamine (1–10 mg/kg) was administered SC 45 min before the animals were killed. Serotonin, 5-hydroxyindole-3-acetic acid (5-HIAA), dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and noradrenaline were measured by high performance liquid chromatography coupled with electrochemical detection (HPLC-ECD) and 3-methoxy-4-hydroxyphenylethyl-eneglycol (MHPG) was measured by HPLC coupled with fluorimetric detection. Ratios 5-HIAA/5-HT, DOPAC + HVA/DA and MHPG/NA were taken as an index of serotonin, dopamine and noradrenaline turnovers, respectively. Tripelennamine (1 and 10 mg/kg) significantly reduced serotonin turnover in control and morphine-dependent mice, and potentiated the serotonin turnover reduction when it was administered 30 min before naloxone injection. The dopamine turnover was diminished by tripelennamine (1 and 10 mg/kg) in the morphine-dependent group. Tripelennamine (10 mg/kg) reduced noradrenaline turnover during abstinence. These results suggest that the potentiation of opiate abstinence by tripelennamine could be related to its antiserotonergic profile.     

Locomotor activity in morphine-dependent and post-dependent rats

The effects of morphine and naloxone were compared on the locomotor activity of nondependent, morphine-dependent, and post-dependent rats. Dependence was induced and maintained for 30 weeks by scheduled access to 0.05% morphine solution for 10 min every 6 hr. Locomotor activity in nondependent and dependent animals was increased by low doses of morphine and reduced by higher doses. Both components were antagonized by naloxone. Chronic morphine treatment produced marked tolerance to the depressant effect of high morphine doses, but not to the stimulant effect of low doses. Post-dependent animals remained tolerant to the depressant effect of high doses of morphine. The development of tolerance to the depressant but not to the stimulant effect of morphine in dependent and post-dependent animals suggests that different neuronal substrates mediate morphine-induced stimulation and depression of locomotor activity. Abrupt or naloxone-precipitated withdrawal generally disrupted locomotor activity in dependent rats. Naloxone alone also decreased activity in post-dependent animals. Thus, chronic morphine administration produces long-lasting changes in the sensitivity of dependent and post-dependent rats to the effects of morphine and naloxone on locomotor activity.     

Schedule-controlled behavior in the morphine-dependent rat

The behavioral effects of acute and chronic administration of morphine and its withdrawal were studied using schedule-controlled responsing in the rat under a differential reinforcement of low rates of responding (DRL) schedule of food presentation. Acute morphine administration had a biphasic effect on response rate. Low doses (1.8–5.6 mg/kg) tended to produce a small increase and higher doses (10–30 mg/kg) decreased responding. Physical dependence was produced by twice daily injections, with an initial dose of 40 mg/kg/day which was increased by 80 mg/kg/day until reaching 600 mg/kg/day which was continued for 14 days. Throughout chronic administration the pattern of responding remained disrupted resulting in a 27–47 percent decrease presentations of the reinforcer, while response rate was more variable and generally decreased. The effects of morphine withdrawal lasted 5 days and produced an initial marked decrease in reinforcements per hour and a biphasic change in response rate. A marked decrease in responding early in withdrawal (22.5 hr) was followed by a marked and more prolonged (70.5–118.5 hr) response rate increase.     

Increased synthesis and release of 3H-histamine in rat brain by reserpine

The brain stores of histamine were labelled by intraventricular administration of ³H-L-histidine. Immediately after reserpine administrations, there was an accelerated decline of ³H-histamine. In rats reserpinized 24 hr earlier, the rate of ³H-HA synthesis was increased by 40%. In both cases, reserpine treatment impaired methylation of ³H-histamine.     

Influence of histamine,cimetidine and pyrilamine on naloxone-induced jumping in morphine-dependent mice

In the present study, the effects of histamine on naloxone-induced jumping in the presence or absence of adrenoceptor or acetylcholine receptor antagonists in morphine-dependent mice were examined. In these experiments, the drugs were used before s.c. injection of naloxone (2 mg/kg), to test their effects on the expression of jumping. The i.c.v. administration of histamine (5-20 microg/mouse) 15 min before naloxone injection decreased the number of jumps in mice. When the histamine H(2) receptor antagonist, cimetidine (5-20 mg/kg), and the histamine H(1) receptor antagonist, pyrilamine (5-20 mg/kg), were administered i.p. to morphine-dependent mice, only cimetidine enhanced the jumping behaviour. Administration of cimetidine (20 mg/kg, i.p.), 30 min, of the beta-adrenoceptor antagonist, propranolol (2.5-10 mg/kg, i.p.), 15 min but not of pyrilamine (20 mg/kg, i.p.), 30 min before naloxone injection, decreased the histamine effect. The i.p. administration of an acetylcholine receptor antagonist, atropine (5 and 10 mg/kg, i.p.), the alpha(1)-adrenoceptor antagonist, prazosin (0.5, 1 and 2 mg/kg, i.p.), and alpha(2)-adrenoceptor antagonist, yohimbine (0.5, 1 and 2 mg/kg, i.p.), 15 min before naloxone injection, had no effect on the histamine response. Single administration of propranolol, atropine or prazosin decreased, while yohimbine increased the naloxone-induced jumping. It is concluded that the histamine H(2) receptor mechanism may be involved in the influence of histamine on the expression of naloxone-induced jumping in morphine-dependent mice.     

Effect of pretreatment with pertussis toxin on the development of physical dependence on morphine

Summary The effect of intracerebroventricular (i.cv.) pretreatment with pertussis toxin (PTX) on the development of physical dependence on morphine was investigated in mice. Twenty four hours after PTX (0.5 g, i.c.v.) or vehicle pretreatment, the mice were chronically treated with morphine (8–45 mg/kg, s.c.) for 5 days. Several withdrawal signs were observed following naloxone challenge in morphine-dependent mice which had been pretreated with vehicle. In addition, 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) and noradrenaline (NA) turnover (MHPG/NA) levels in the cerebral cortex were increased following naloxone challenge in morphine-dependent mice. These findings indicate that activation of the central noradrenergic system may mediate the expression of some withdrawal signs. In contrast, pretreatment with PTX attenuated the naloxone-precipitated withdrawal signs in morphine-dependent mice. The incidence of withdrawal signs such as jumping, wet dog shakes, and rearing was significantly reduced by PTX pretreatment. PTX pretreatment also prevented the naloxone-precipitated increases in MHPG concentration and NA ratio (MHPG/NA) in the cerebral cortex, suggesting that central PTX-sensitive GTP-binding proteins (G-proteins) may be involved in the elevation of NA transmission in the cortex which projects from the locus coeruleus (LC) during morphine withdrawal.The blocking effects of PTX on the behavioral and biochemical changes after withdrawal suggest that central PTX-sensitive G-proteins (Gi/Go) may play an important role in the development of physical dependence on morphine.Correspondence to: Tsutomu Suzuki at the above address     

Effects of morphine on the turnover of brain catecholamines and serotonin in rats — chronic morphine administration

The turnover of brain monoamine was studied in rats in which different degrees of tolerance to and dependence on morphine were induced by pellet implantation. The degree of tolerance to morphine was assessed by measuring the increase in effective dose for an antinociceptive effect (vocalization test). The rate of depletion of brain dopamine (DA) and serotonin (5-HT) after α-methyl-p-tyrosine (AMT) or α-propyl-dopacetamide (dop-acetamide) was not changed by chronic morphine treatment. In contrast, the accumulation of brain homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) after probenecid was significantly increased, but there was no correlation between the biochemical changes and the degree of tolerance/dependence of the animals; at a very high degree of dependence 5-HIAA accumulation even became normal. In rats in which smaller amounts of morphine were repeatedly injected every 8 hr for 1 week the increased accumulation of HVA and 5-HIAA persisted in spite of complete tolerance to the antinociceptive effect.The rate of depletion of brain noradrenaline (NA) after AMT or dopacetamide was not changed and the accumulation of brain 3-methoxy-4-hydroxy-phenylglycol sulphate (MHPG-SO₄) after probenecid was not affected in most chronic morphine groups. In the group with the highest degree of tolerance/dependence NA depletion after AMT was even retarded.The results suggest that chronic morphine treatment increases the synthesis and the intraneuronal destruction of newly synthesized DA and 5-HT without changing the rate of functional utilization of the monoamines. It is unlikely that the changes in monoamine metabolism are causally related to processes leading to morphine tolerance/dependence.     

Influence of apomorphine on brain serotonin turnover rate.

Apomorphine (5.0 mg/kg) accelerated the disappearance of 5-HIAA from the brain of pargylinepretreated rats as well as depletion of brain 5-HT caused by inhibition of its synthesis. The latter effect has been abolished by spiroperidol. The results obtained suggest that apomorphine increases the 5-HT turnover rate, secondary to the stimulation of central dopamine receptors.     

Antagonist-precipitated and discontinuation-induced withdrawal in morphine-dependent rhesus monkeys

Rationale  Upon discontinuation of chronic opioid treatment, withdrawal typically peaks in 1–3 days and decreases markedly within 1 week; however, persistent physiological changes have been reported long after other signs have waned. Objective  The goal of this study was to compare the discriminative stimulus, directly observable signs, and physiological effects of withdrawal in morphine-treated monkeys. Materials and methods  Monkeys received 5.6 mg/kg/12 h morphine and discriminated 0.0178 mg/kg naltrexone while responding under a fixed-ratio 5 schedule of stimulus–shock termination. Drug discrimination, behavioral observation, and telemetry were used to monitor the emergence of withdrawal, as well as any persistent changes, following discontinuation of morphine treatment. Results  Naltrexone dose (0.001–0.032 mg/kg, s.c.) was positively related with indices of withdrawal. In the discrimination study, monkeys responded on the naltrexone lever 1–5 days following discontinuation of treatment; thereafter, they responded exclusively on the saline lever. After discontinuation of morphine, the frequency of observable signs peaked within 2–3 days and most were not significantly increased after 5 days. In contrast, increased heart rate and body temperature persisted for 14 days, returning to values obtained prior to discontinuation by 21 days. Conclusions  To the extent that discriminative stimulus effects of withdrawal in nonhumans are predictive of subjective reports of withdrawal in humans, these data indicate that effective treatments for opioid dependence must address not only the short-term subjective components of withdrawal but also, and perhaps more importantly, lingering behavioral and physiological effects that might contribute to relapse long after chronic drug use is discontinued. This project was supported by USPHS Grants DA05018 and DA17918 from the National Institute on Drug Abuse. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute on Drug Abuse or the National Institutes of Health.     

Evidence of a preferential role of brain serotonin in the mechanisms leading to naloxone-precipitated compulsive jumping in morphine-dependent rats

Various drugs acting on brain serotonin or catecholamines were administered concurrently with morphine during the development of dependence or before naloxoneprecipitated withdrawal syndrome. Of the various drugs only cyproheptadine, a serotonin antagonist, and piribedil, a dopamine agonist, reduced the frequency of jumping (but not of diarrhea or ptosis) when administered with morphine during development of dependence. When administered before naloxone, d-fenfluramine, a serotonin releaser, markedly reduced jumping, but not diarrhea and ptosis, and clonidine blocked these latter signs without affecting the frequency of jumping. Of the other drugs examined only phenoxybenzamine reduced diarrhea in morphine-abstinent rats. It is suggested that serotonin is involved in the mechanisms which lead to compulsive jumping during naloxoneprecipitated withdrawal, whereas adrenergic sites on which clonidine acts are mainly involved in the expression of signs, such as ptosis and diarrhea. No clear evidence was obtained of a role for dopamine in the withdrawal signs studied.     

The effect of atropine on the turnover of acetylcholine in the mouse brain.

The effect of atropine on the acetylcholine (ACh) turnover in the mouse brain has been studied and related to the central effect (motor activity) of the drug. At the threshold dose for maximal increase in motor activity, atropine had no measurable effect in the brain on the initial rate of formation of labelled ACh from labelled choline (Ch) i.v. injected. However, if atropine was injected 3 min after the injection of labelled Ch, when the labelled ACh had reached its peak value in the brain, there was a more rapid exponential decline of labelled ACh. This was assumed to be an indication that atropine increases the turnover of ACh in the brain. The specific radioactivity of ACh was not changed 2-17 min after the atropine injection, which indicates that atropine does not preferentially increase the release of newly synthetized ACh.     

Histamine,histidine decarboxylase and histamine-N-methyltransferase in brain areas of spontaneously hypertensive rats

Summary Histamine levels, histidine decarboxylase and histamine-N-methyltransferase activities were determined in various brain areas of young (9-week old) and adult (18-week old) normotensive rats (WKY) and hypertensive rats (SHR). When compared with WKY, histamine levels were increased in the anterior and posterior hypothalamus of young and adult SHR, as well as in the brainstem of young SHR. Histidine decarboxylase activity was unchanged in the posterior hypothalamus and in the medulla oblongata of young and adult SHR as well as in the anterior hypothalamus of young SHR, but it was slightly decreased in the anterior hypothalamus of adult SHR. Histidine decarboxylase activity was enhanced in the cortex-midbrain of young, as well as adult SHR, histamine-N-methyltransferase in the cortex-midbrain of young SHR. The following differences were found between young and adult rats: histamine levels were elevated in the cortex-midbrain of adult WKY and SHR. In the cortex-midbrain and brainstem of adult WKY and SHR histidine decarboxylase activity was also increased, while histamine-N-methyltransferase activity was elevated in the cortex-midbrain of adult WKY. The findings show changes in histamine levels, histidine decarboxylase and histamine-N-methyltransferase activities in SHR and suggest involvement of histaminergic neurons in hypertension. The activity of histaminergic neurons of adult rats seems to be higher than that of young animals.This work was supported by the Fonds zur Förderung der wissenschaftlichen Forschung (P5750) Send offprint requests to H. Prast at the above address     

Involvement of opioid receptors in phencyclidine-induced enhancement of brain histamine turnover in mice

Summary When the histamine (HA) turnover in the brain of mice was estimated on the basis of the pargyline-induced accumulation of tele-methylhistamine (t-MH), a predominant metabolite of brain HA, the enhancing effect of phencyclidine (PCP) on the HA turnover was antagonized by a large dose of naloxone. However, a dopamine receptor antagonist haloperidol, which is also a potent receptor antagonist, did not inhibit the effect of PCP on the HA turnover. [abetd-Ala², abetd-Leu⁵]enkephalin, a prototypic opioid agonist, markedly enhanced the HA turnover. The effect of this peptide was demonstrated not only when the HA turnover was determined by the pargyline-induced t-MH accumulation but when it was estimated by the HA depletion induced by -fluoromethylhistidine, a specific inhibitor of histidine decarboxylase. A agonist, SKF-10047, and a agonist, ethylketazocine, had no PCP-like enhancing effect on the HA turnover. These results suggest that PCP enhances the brain HA turnover in mice by stimulating, probably indireclty, endogenous opioid systems. Send offprint requests to K. Saeki at the above address     

Effect of acutely administered analgesic drugs on rat brain serotonin turnover

Rat brain 5-HT levels were unaltered by all four analgesics. Levels of 5-HAA in the rat brain were increased by morphine and decreased by pethidine. The effect of morphine, but not pethidine, on 5-HIAA levels was antagonized by naloxone pretreatment. Rat brain 5-HT turnover was measured by two non-isotopic techniques. Of morphine, pentazocine, methadone and pethidine only morphine increased brain 5-HT turnover. Furthermore, morphine increased brain tryptophan levels. The ability of morphine to increase both 5-HT turnover and tryptophan levels was antagonized by naloxone pretreatment. Pethidine also increased brain tryptophan levels but this effect was not antagonized by naloxone. It is concluded that the ability of morphine to increase rat brain 5-HT turnover is not possessed by pentazocine, methadone and pethidine.     

Effects of reserpine on brain and liver glycogen levels after pretreatment with pargyline in isolated and aggregated mice

Summary 1.5 mg/kg reserpine given after pargyline is about the LD₅₀ in aggregated mice and induces no lethality in isolated mice. In the aggregated group the mice died after a state of exhaustion. Brain and liver glycogen did not change in the isolated group. In the aggregated group in the state of depression the liver glycogen decreased, the brain glycogen did not change. During the excitation the brain glycogen increased, the liver glycogen however did not show any alteration.     

Some relations between tolerance and physical dependence to morphine in mice

Tolerance to morphine analgesia and precipatated physical dependence were studied in mice under different conditions. There was a gradual loss of tolerance during the continous absorption of morphine from a pellet. Tolerance was decreased by nalorphine during morphine absorption. An attenuated physical dependence was observed two or four days after a single dose of morphine. In animals previously treated with pellets of morphine, single doses of morphine induced less tolerance than in mice that had never been implanted with pellets; in both cases cycloheximide prevented development of tolerance. Tolerance persisted for more than 20 days after absorption of the morphine pellet. These results reinforce the hypothesis that tolerance and physical dependence are produced by a similar mechanism and that an inhibitory process of tolerance exists.