Tachykinin antagonists inhibit the morphine withdrawal response in guinea-pigs

Summary This study was an investigation of the effects of the tachykinin antagonists, spantide and (d-Pro⁴, d-Trp^{7, 9, 10})substance P 4-11, injected intracerebroventricularly (ICV), on the locomotor and behavioural responses of guinea-pigs to substance P (SP) injected ICV and to naloxone-induced morphine withdrawal. SP, 50 nmol, produced increased locomotor activity and behaviour that mimicked the response induced by injection of naloxone hydrochloride, 15 mg/kg, in guinea-pigs treated 2 h previously with morphine sulphate, 15 mg/kg. Spantide or (d-Pro⁴, d-Trp^{7, 9, 10})SP4-11, 10 nmol, reduced the locomotor and behavioural responses to SP and to morphine withdrawal. The results support the suggestion that SP or a related tachykinin might be a mediator of the opioid withdrawal response in the central nervous system as has been proposed for the enteric nervous system.     

The properties of the clonidine withdrawal response of guinea-pig isolated ileum.

The dependence-inducing effects of clonidine were investigated on the guinea-pig isolated ileum. Clonidine produced relaxation of the ileum with a threshold concentration between 0.01 and 0.1 mumol 1(-1). Washout of clonidine did not induce a withdrawal contraction. Following 2 min contact of the ileum with clonidine, 1 mumol 1(-1), addition of phentolamine, 5 mumol 1(-1), induced a contracture. The phentolamine-precipitated withdrawal contracture did not increase in height with a longer period of contact (32 min) of the ileum with clonidine. The phentolamine-precipitated withdrawal contracture following 2 min contact of ileum with clonidine was abolished by atropine, 5 mumol 1(-1), and substance P (SP) antagonists, (D-Pro2,D-Phe7, D-Trp9)-SP and spantide, 10 mumol 1)-1). [Met5]enkephalin, 1 mumol 1(-1), abolished the withdrawal response to clonidine and clonidine, 1 mumol 1(-1), abolished the withdrawal response to [Met5]enkephalin. Following 2 min contact of the ileum with noradrenaline, 5 mumol 1(-1), washout or addition of phentolamine or yohimbine, 5 mumol 1(-1), also induced a withdrawal response. The noradrenaline washout withdrawal response was abolished by atropine, 5 mumol 1(-1), and spantide, 10 mumol 1(-1). Since clonidine dependence may be induced as rapidly as opiate dependence in the ileum and the pharmacology of the withdrawal responses is similar, it is suggested that they both induce the same post-receptor neuronal feedback disturbance in which substance P neurones play a major role.     

Precipitated and conditioned withdrawal in morphine-treated rats

Rationale  

Stimuli that are paired with opioid withdrawal can themselves produce effects similar to withdrawal that might promote relapse.     

Capsaicin pretreatment does not inhibit the opioid withdrawal response in guinea-pigs

The effects of capsaicin pretreatment on withdrawal responses of guinea-pig isolated ileum to [Met5]enkephalin (ME) and morphine and on the locomotor withdrawal response of guinea-pigs following a single dose of morphine, were investigated. In vitro treatment of ileum with capsaicin, 1.5 mumol/l for 1 h, did not significantly affect the response to washout following 2 min contact with ME, 1 mumol/l, or the withdrawal response precipitated by naloxone, 1 mumol/l, following 2 min contact with morphine, 1 mumol/l, or the response to naloxone of tolerant-dependent ileum obtained from guinea-pigs treated with a total dose of 690 mg/kg of morphine over 3 days. Pretreatment of guinea-pigs with capsaicin 140 mg/kg subcutaneously (s.c.) over 4 days also did not affect the washout withdrawal response of the ileum to ME. Pretreatment of guinea-pigs with capsaicin did not affect the locomotor withdrawal response precipitated by naloxone hydrochloride 15 mg/kg s.c., 2 h after injection of morphine sulphate 15 mg/kg s.c. It was concluded that primary afferent neurones do not play an essential role in opioid withdrawal responses.     

The effect of clonidine withdrawal on total 3-methoxy-4-hydroxyphenylglycol in the rat brain

The effect of clonidine withdrawal on the brain norepinephrine system was studied in the rat. Clonidine suppresses brain total 3-methoxy-4-hydroxyphenylglycol (MHPG) significantly and no tolerance to this effect was observed up to 21 days. Cessation of clonidine treatment resulted in an elevation in the level of brain total MHPG. The suitability of the clonidine withdrawal syndrome as a model of bipolar depression is discussed.Ontario Mental Health Foundation Research Fellow 1977–1978     

Failure of cholecystokinin to precipitate withdrawal in morphine-treated rats

In a test of the possible antagonistic interaction between cholecystokinin (CCK) and morphine, morphine-dependent rats were injected with one of three doses of CCK or with naloxone immediately following the consumption of a novel saccharin solution. Whereas opiate-dependent rats injected with the opiate antagonist naloxone acquired an aversion to the saccharin solution (and displayed a dramatic weight loss), CCK was without effect. These data were discussed in relation to the possible pharmacological antagonism between CCK and the opiates.     

Studies in the rat on the haemodynamic overshoot response to withdrawal of guanfacine or clonidine treatment

1. Normal rats were injected intramuscularly twice daily for either 3 days or 3 weeks with guanfacine (0.1 or 1.0 mg/kg), clonidine (0.01 or 0.1 mg/kg) or 0.9% saline. All were anaesthetized at various times before or after the last injection, and their arterial pressures and heart rates were monitored via a carotid artery catheter. 2. Overshoots in systolic and diastolic pressure and heart rate, reaching peak values as soon as 16 h after the last injection, occurred in all rats withdrawn from guanfacine or clonidine treatment, but in no control rats. 3. Post-withdrawal blood pressures and heart rates of rats which had received the low dose of guanfacine or clonidine were as great as those of rats which had received the ten-fold greater dosage. Moreover, withdrawal responses were as great in rats which had been treated for only 3 days as in those treated for 3 weeks. 4. The dosages and duration of treatments used in these experiments thus did not influence the magnitude of the haemodynamic overshoots provoked by withdrawal of guanfacine or clonidine. However, all groups of rats from which guanfacine was withheld exhibited significantly greater peak overshoots in systolic and diastolic pressure than did those withdrawn from clonidine treatment.     

Sensitization to morphine withdrawal in guinea-pigs

The aim of this study was to determine whether sensitization occurred to morphine withdrawal. Guinea-pigs were treated twice daily with increasing doses of morphine (10-100 mg/kg s.c.) for 3 days followed by injection of morphine 100 mg/kg on the fourth day. Sixty min after the last morphine injection, animals were withdrawn from morphine with naltrexone, 15 mg/kg s.c., and locomotor activity and all other behaviours scored over 90 min. Animals were then rested for 3 days. This procedure was repeated twice over the next 2 weeks. Control animals were treated with saline for the first two treatment cycles. Guinea-pigs subjected to three cycles of morphine withdrawal showed a significant increase in the total number of withdrawal behaviour counts over the 90-min observation period following the third cycle of withdrawal compared with the first and second withdrawal cycles. However, locomotor activity, a major sign of morphine withdrawal in guinea-pigs, was not significantly increased. Fos-LI was markedly increased in the repeatedly withdrawn animals in several brain regions, including amygdala, dorsal striatum, thalamus, ventral tegmental area, and ventrolateral periaqueductal gray area. It is concluded that sensitization to morphine withdrawal occurs in guinea-pigs.     

Effects of opioid and alpha 2-adrenoceptor agonists on the isolated ileum of morphine-dependent guinea-pigs during withdrawal and after clonidine treatment.

The present study was undertaken to investigate the effect of clonidine administration to opiate-dependent guinea-pigs after morphine withdrawal on subsequent twitch responses of the longitudinal muscle-myenteric plexus preparations to electrical field stimulation. The results indicate that clonidine, administered immediately after morphine removal, causes tolerance to the inhibition exerted by opioid and alpha 2-adrenoceptor agonists on the electrically-evoked twitches. Such a finding suggests that the mechanism of action of clonidine involves not only its well-known effects on locus coeruleus neurons but also that it has specific actions on the myenteric plexus. This work shows the existence of interactions between opioid and alpha 2-adrenoceptor on the cholinergic neurons present in the isolated ileum.     

Failure of clonidine treatment in benzodiazepine withdrawal

Six subjects, dependent on benzodiazepines for at least 2 years, were gradually withdrawn, using placebo substitution, while taking clonidine. After withdrawal was complete, subjects were switched to clonidine-placebo. Despite administration of clonidine at doses sufficient to produce a fall in blood pressure, an abstinence syndrome was seen in five of the subjects. In none of these cases was the withdrawal syndrome exacerbated by changing from clonidine to clonidine-placebo. Scores of depression, subjective anxiety, observed anxiety and somatic symptoms did not change throughout the study.     

Effects of clonidine on morphine withdrawal signs in the rat.

The influence of clonidine on the naloxone-induced withdrawal signs, escape attempts and precipitated shakes, was studied in morphine-dependent rats. Clonidine injected i.p. or intraventricularly (i. vent.) inhibited precipitated shakes and potentiated escape attempts induced by naloxone in morphine-dependent rats. Under pentobarbital anesthesia, precipitated shakes and ice water-induced wet shakes were inhibited by clonidine and norepinephrine. Clonidine injected i. vent. reduced body temperatures in morphine-dependent rats but not in placebo pellet-implanted rats. We suggest that clonidine modulates morphine withdrawal signs by potentiating the behavior associated with heat dissipation (escape attempts) and inhibiting the behavior associated with heat gain mechanisms (precipitated shakes). These effects may occur via stimulation of central noradrenergic mechanisms.     

Blind study of the effect of the alpha-adrenergic agonists clonidine and lofexidine on alcohol withdrawal in the rat

Alpha-adrenergic agonists have been reported to block the opiate withdrawal reaction in animals and humans, probably by interference with the catecholaminergic hyperactivity that prevails during opiate withdrawal. Since catecholaminergic hyperactivity also occurs during alcohol withdrawal, the present study investigated whether the central alpha-adrenergic agonists clonidine and lofexidine could interfere with this type of withdrawal reaction. During withdrawal from a 4-day intoxication period, male Wistar rats were assigned to one of three groups: clonidine treatment (0.15 mg/kg, N = 11), lofexidine treatment (0.50 mg/kg, N = 11) and control (N = 11). The study was performed blind, the code for the saline control and two drug treatment groups being broken only after the last rating of withdrawal symptoms. Since neither clonidine nor lofexidine modified the development or degree of the alcohol withdrawal reaction, there was no support for the assumption of a common mechanism involving the alpha-adrenergic system during opiate and alcohol dependence.     

Effect of clonidine, nimodipine and diltiazem on the in vitro opioid withdrawal response in the guinea-pig ileum.

1. The effects of clonidine, nimodipine and diltiazem, on the in vitro withdrawal contracture induced by naloxone in the guinea-pig ileum obtained from morphine-dependent animals, were evaluated. 2. The in vitro incubation with clonidine (0.01, 0.1 and 1 microM), diltiazem (0.25, 0.1 and 1 microns) or nimodipine (0.05, 0.1 and 1 microns) reduced significantly the force of the contracture induced by naloxone in the morphine-dependent guinea-pig ileum. 3. The intraperitoneal administration of clonidine (0.3 mg kg-1), nimodipine (5 mg kg-1) or diltiazem (20 mg kg-1) reduced the contractile response induced by naloxone in the morphine-dependent guinea-pig ileum. 4. It is concluded that at least part of the effect of clonidine, nimodipine and diltiazem on withdrawal contractures is mediated via a peripheral, rather than a central site of action. Even though, the mechanism responsible for the effect of the calcium channel blockers differs from that of alpha 2-adrenoceptor agonists, all of the drugs tested prevented the contracture induced by naloxone in morphine-dependent guinea-pig ileum.     

Location of the mechanism of the clonidine withdrawal tachycardia in rats

Withdrawal of chronic infusion of clonidine elicits severe tachycardia and short-lasting blood pressure elevations (upswings). Withdrawal of clonidine in low dosage (30 micrograms kg-1 day-1 i.c.v., 7 days) elicited a maximum of 10.9 +/- 0.5 upswings h-1. Cessation of s.c. infusion of clonidine (30 micrograms kg-1 day-1 7 days) evoked a maximum of 1.9 +/- 0.5 upswings h-1. After cessation of the two clonidine infusions no overshoot of heart rate occurred. Withdrawal of a higher dose of clonidine (300 micrograms kg-1 day-1 s.c., 7 days), however, induced tachycardia (from 302 +/- 8 to 433 +/- 8 beats min-1) and 7.6 +/- 1.4 upswings h-1. The administration of the alpha 2-adrenoceptor antagonist yohimbine precipitated withdrawal tachycardia in animals treated with oxymetazoline, a hydrophilic alpha-adrenoceptor agonist. Yohimbine (3 mg kg-1 i.p.) precipitated a severe rise in heart rate from 285 +/- 14 to 520 +/- 5 beats min-1 in oxymetazoline (300 micrograms kg-1 day-1 s.c., 7 days) treated rats and from 320 +/- 13 to 420 +/- 11 beats min-1 in saline-treated animals. Upswings were not induced by yohimbine treatment. It is concluded, that the blood pressure upswings after clonidine withdrawal are due to a central mechanism, whereas the mechanism of the overshoot of heart rate is located peripherally, probably at the cardiac presynaptic level.     

Effects of clonidine and morphine on opioid withdrawal in rhesus monkeys

Rhesus monkeys undergoing opioid withdrawal either due to withholding morphine administration for 14 h or due to administration of naloxone, were treated with either morphine or clonidine. Morphine eliminated all of the withdrawal signs that developed when morphine was withheld for 14 h. Clonidine also eliminated some but not all signs that developed when morphine was withheld. The frequencies of individual signs prior to drug administration were directly related to the minimal doses necessary to eliminate signs for morphine but not for clonidine. Morphine also eliminated most of the signs precipitated by naloxone, whereas clonidine did not eliminate as many of the naloxone-precipitated signs. Additionally, some of the naloxone-precipitated signs that were eliminated by clonidine were not eliminated by morphine. The present results are consistent with clinical findings indicating an efficacy of clonidine in the treatment of opioid withdrawal through a non-opioid mechanism.     

Efficacy of clonidine in treatment of alcohol withdrawal state

Clonidine hydrochloride 5 micrograms/kg and placebo were given orally to 11 patients experiencing well-developed alcohol withdrawal states. Active drug and placebo were given in a randomised, cross-over double blind fashion 2 h apart. Clonidine significantly suppressed heart rate (P = 0.002), arterial blood pressure (P = 0.006), and an accumulated score of withdrawal symptoms and signs (P = 0.004). These data suggest that clonidine may be useful in the management of alcohol withdrawal states, and that the underlying pathophysiology of at least some of these manifestations may be sympathetic nervous system hyperactivity.     

The effect of clonidine on the response to stimulation of non-adrenergic non-cholinergic nerves in the guinea-pig urinary bladder in-vitro

The effects of clonidine on the response of the guinea-pig urinary bladder detrusor muscle to stimulation of non-adrenergic non-cholinergic (NANC) nerves were investigated in-vitro. In tissues from both treated and chemically sympathectomized animals, in the presence of atropine (10^?5 M) to inhibit cholinergic responses, clonidine (10^?10-10^?6 M) invariably enhanced the contractile response to NANC nerve stimulation at 2, 5, 10 and 20 Hz. The enhancement was not inhibited by yohimbine (10^?5 M), phentolamine (10^?5 M), or the histamine H₁ or H₂-receptor antagonists mepyramine (10^?6 M) or cimetidine (10^?5 M) respectively. Phentolamine (10^?5 M), like clonidine, enhanced the response to stimulation of NANC nerves at 2, 5, 10 and 20 Hz. Xylazine, another α₂-agonist, which, unlike both clonidine and phentolamine, is not a substituted 2-imidazoline compound, failed to enhance the response in the bladder to NANC nerve stimulation. The results suggest that clonidine enhances the response to NANC nerve stimulation, independently of its effects on α-adrenoceptors, by increasing the amount of NANC transmitter available.     

正通宁与可乐定对阿片类戒断症状的实验研究

目的　比较正通宁和可乐定对动物阿片类戒断症状的抑制作用。方法　以吗啡依赖性和海洛因依赖性小鼠和大鼠的催促戒断模型、猴自然戒断模型 ,给予不同剂量正通宁片和可乐定 7d ,观察结果。结果　①正通宁 2个剂量 (0 75、1 5 g/kg)能显著减轻吗啡和海洛因依赖性小鼠在纳洛酮催促下引起的跳跃反应和体重丧失 (P <0 0 5～ 0 0 1) ;②正通宁 2个剂量 (0 75、0 5 g/kg)能显著抑制吗啡和海洛因依赖性大鼠在纳洛酮催促下引起的戒断症状和体重下降 (P <0 0 5～ 0 0 1)。③在吗啡依赖性猴模型上 ,正通宁 3个剂量 (0 2、0 6、1 0 g/kg)给灌胃每天 3次 ,连续 7d ,均能不同程度地抑制吗啡依赖性猴的戒断症状 ,其中以高剂量组的效果最好。在停吗啡后的头 3d ,高剂量组猴的戒断症状得到了明显的控制 ,戒断症状分低于NS组 ,7d戒断总平均分明显低于NS组 ,统计学处理差异有显著性 (P <0 0 5～ 0 0 1) ,疗效似比可乐定好。结论　正通宁对阿片类依赖动物戒断症状的脱毒治疗效果肯定 ,效能优于可乐定     

Changes in locomotor-activity patterns as a measure of spontaneous morphine withdrawal: no effect of clonidine

The anti-withdrawal action of clonidine was studied in a model of spontaneous morphine withdrawal in rats. After withdrawal the behaviour of the animals was registered continuously for several days. In the initial phase of induction of dependence the locomotor activity was enhanced during daytime. Partial tolerance to this increase developed in the course of 3 weeks. In morphine withdrawn animals the activity decreased strongly at night, and this effect was maximal on the second night after removal of morphine. After four nights the nightly activity was restored. Treatment with clonidine (100 micrograms/kg s.c. twice daily) changed neither the observed decrease in nightly locomotor activity nor other withdrawal symptoms such as a decrease in food intake and loss of body weight. In non-dependent animals clonidine induced a biphasic effect in locomotor activity, i.e. a decrease in the first few hours of the night and an increase in the second part of the night. The latter can be interpreted as a rebound phenomenon occurring after only three injections. It was concluded that clonidine was not effective as an anti-withdrawal compound in a model for spontaneous morphine abstinence. The low incidence of symptoms relating to a hyperactive sympathetic system during spontaneous withdrawal may be an explanation for the absence of an effect of clonidine.