CGS8216 noncompetitively antagonizes the discriminative effects of diazepam in rats

The benzodiazepine antagonist properties of CGS8216 were evaluated in rats trained to discriminate between saline and 1.0 mg/kg of diazepam in a two-choice, stimulus-shock termination procedure. CGS8216 (0.3 to 100 mg/kg) administered alone, either s.c., p.o. or i.p., occasioned only saline-appropriate responding. When administered concomitantly with a constant 1.0 mg/kg dose of diazepam, CGS8216 produced dose-related decreases in drug-appropriate responding. CGS8216 was most potent by the i.p. route, and approximately tenfold less potent by the oral route. CGS8216 was dermatotoxic after s.c. administration. CGS8216 i.p. had a long duration of action. A dose of 30 mg/kg completely antagonized the discriminative effects of the 1.0 mg/kg training dose of diazepam when the antagonist was administered 8 hr before the start of the test session. In order to determine the type of antagonism by CGS8216, the dose-effect curve for diazepam was redetermined in the presence of varying doses of CGS8216 (0.3 to 3.0 mg/kg, i.p.). CGS8216 produced a dose-related rightward shift in the diazepam dose-effect curve, but also decreased the slope and appeared to decrease the maximal effect. These results are consistent with the interpretation that CGS8216 antagonizes diazepam in a noncompetitive manner. It may do so because either it interacts with a subpopulation of benzodiazepine receptors, it functions as a pseudo-irreversible antagonist due to its high affinity, or because it is an antagonist with agonist properties.     

Attenuating effect of diazepam on stress-induced increases in noradrenaline turnover in specific brain regions of rats: antagonism by Ro 15-1788

One-hour immobilization stress increased levels of the major metabolite of brain noradrenaline (NA), 3-methoxy-4-hydroxyphenyl-ethyleneglycol sulfate (MHPG-SO4), in nine brain regions of rats. Diazepam at 5 mg/kg attenuated the stress-induced increases in MHPG-SO4 levels in the hypothalamus, amygdala, hippocampus, cerebral cortex and locus coeruleus (LC) region, but not in the thalamus, pons plus medulla oblongata excluding the LC region and basal ganglia. The attenuating effects of the drug on stress-induced increases in metabolite levels in the above regions were completely antagonized by pretreatment with Ro 15-1788 at 5 or 10 mg/kg, a potent and specific benzodiazepine (BDZ) receptor antagonist. When given alone, Ro 15-1788 did not affect the increases in MHPG-SO4 levels. Behavioral changes observed during immobilization stress such as vocalization and defecation, were also attenuated by diazepam at 5 mg/kg and this action of diazepam was antagonized by Ro 15-1788 at 10 mg/kg, which by itself had no effects on these behavioral measurements. These findings suggest: (1) that diazepam acts via BDZ receptors to attenuate stress-induced increases in NA turnover selectively in the hypothalamus, amygdala, hippocampus, cerebral cortex and LC region and (2) that this decreased noradrenergic activity might be closely related to relief of distress-evoked hyperemotionality, i.e., fear and/or anxiety in animals.     

Cortexolone as a modulator of diazepam activity

The influence of ACTH (200 micrograms/kg), corticosterone (20 mg/kg) and cortexolone (20 mg/kg) on the anxiolytic activity of diazepam was studied. ACTH partly and corticosterone completely blocked the action of diazepam. Cortexolone injection 30 min before the administration of diazepam induced a 100% anxiolytic effect of diazepam in the range of doses from 0.1 to 0.3 mg/kg (ED50 of anxiolytic diazepam effect is 0.2 mg/kg). The role of stress hormones in the regulation of psychotropic drug activity is discussed.     

Teratogenic effect of cocaine and diazepam in CF1 mice

This study was conducted to determine the teratogenic effect of cocaine hydrochloride, alone or in combination with diazepam. Pregnant mice were administered cocaine hydrochloride at 10 and 20 mg/kg body weight intravenously (tail), and/or diazepam at 20 or 40 mg/kg b.w. by gavage. Combinations of diazepam and cocaine (20/10 and 40/20, respectively) were used. Significant reductions of fetal weight and length were found in the group treated with diazepam and cocaine (40/20). The incidences of incomplete ossification of sternebrae and skull bones, as well as delayed ossification of the paws, were significantly increased in the combination groups. Hydronephrosis and cryptorchidism were observed in the cocaine-treated groups, with the incidence of these malformations increasing significantly when diazepam was co-administered.     

Ro 15-1788 antagonizes the discriminative stimulus effects of diazepam in rats but not similar effects of pentobarbital

The benzodiazepine antagonist properties of Ro 15-1788 were evaluated in rats trained to discriminate between saline and either 1.0 mg/kg of diazepam or 10 mg/kg of pentobarbital in a two-choice discrete-trial shock avoidance procedure. When administered alone, 1.0 mg/kg of diazepam and 10 mg/kg of pentobarbital produced comparable amounts of drug-appropriate responding (> 84%), whether rats were trained to discriminate between diazepam or pentobarbital and saline. Ro 15-1788 (3–32 mg/kg, p.o.), administered 10 min before diazepam or pentobarbital, produced a dose-related blockade of the discriminative effects of diazepam in both groups of rats, but was completely ineffective in blocking the discriminative effects of pentobarbital. The dose-effect curve for the discriminative effects of diazepam was shifted to the right in a parallel fashion 3- and 13-fold by 10 and 32 mg/kg of Ro 15-1788, respectively, indicating that Ro 15-1788 acts as a surmountable, competitive antagonist of diazepam. When administered alone, Ro 15-1788 (32–100 mg/kg, p.o.) produced primarily saline-appropriate responding, although 100 mg/kg of Ro 15-1788 produced drug-appropriate responding in one out of eight rats. When administered orally 30 min after diazepam, Ro 15-1788 (32 mg/kg) completely reversed within 10 min the discriminative effects of diazepam. The blockade of diazepam's discriminative effects by 32 mg/kg of Ro 15-1788 appeared to last at least as long (approximately 2 hr) as the effects of diazepam alone.     

Effects of melatonin, morphine and diazepam on formalin-induced nociception in mice

The possible analgesic effect of melatonin was investigated in young male ICR mice. The formalin test which elicits typically 2 phases of pain response, the acute (first) phase and tonic (second) phase, was used. The test was performed in the late light period when the mice have been reported to be more sensitive to pain. Compared to control mice, no significant difference in nociceptive response was observed when melatonin was injected intraperitoneally at doses of 0.1, 5, and 20, mg/kg body weight. The combined effects of melatonin with diazepam and/or morphine, were also investigated. Melatonin, injected at 20 mg/kg 15 min before formalin test, significantly increased the antinociceptive response of diazepam (1 mg/kg) or morphine (5 mg/kg) in the second phase. In addition, when melatonin was given at 20 mg/kg together with diazepam and morphine, antinociceptive responses in both the first and second phase were increased. These data indicate the synergistic analgesia effect of melatonin with morphine and diazepam and suggest the possible involvement of melatonin as an adjunct medicine for pain patients.     

Comparison of midazolam and diazepam for sedation during plastic surgery

A randomized double-blind study was designed to compare midazolam, a rapid-acting water-soluble benzodiazepine, with diazepam for sedation when administered as an adjuvant to ketamine during local anesthesia. In the preliminary dose-ranging study, midazolam (0.05 to 0.15 mg/kg IV) was found to produce a spectrum of central nervous system activity (e.g., sedation, amnesia) that was similar to diazepam (0.1 to 0.3 mg/kg IV). However, the slope of midazolam's dose-response curve for sedation appeared to be steeper (i.e., a narrower therapeutic dosage range). In a comparative evaluation of their relative sedative-amnestic properties and recovery characteristics, the median effective doses of the two benzodiazepines were compared. Midazolam (0.1 mg/kg IV) was found to produce more profound sedation and amnesia than diazepam (0.2 mg/kg IV). Midazolam was associated with significantly less pain on injection and a lower incidence of postoperative venoirritation. Overall patient acceptance was higher with midazolam compared to diazepam. Finally, recovery characteristics were similar for the two benzodiazepines in our outpatient setting.     

地西泮和戊巴比妥钠对两种小鼠镇静催眠作用强度的观察

目的：观察地西泮和戊巴比妥纳对不同种属小鼠自主活动和睡眠效应的影响,为筛选影响中枢神经系统功能的药物提供可参考的选择动物的依据。方法：分别取昆明种和ICR小鼠各40只,设对照组和地西泮给药组,每组20只,给药组ig地西泮4mg／kg,对照组给生理盐水,连续3天,末次给药后45分钟测定小鼠自主活动。另取两种小鼠各20只,分别ip戊巴比妥钠50mg／kg,观察两种小鼠的睡眠情况,记录潜伏期和睡眠时间。结果：ICR小鼠ig地西泮后,表现明显的镇静作用,自主活动的次数和对照组比较明显减少,P〈0．01;而昆明种小鼠给相同剂量的地西泮,小鼠自主活动的次数减少不明显,P〉0．05。昆明种和ICR小鼠同样ip阈上剂量的戊巴比妥钠,两者在睡眠潜伏期上无明显差异,但在睡眠时间上,则ICR小鼠的睡眠时间明显长于昆明种小鼠,P〈0．01。结论：ICR小鼠对中枢抑制药的反应性更好,适合于这类药物的筛选,尤其对作用相对较弱的中药制剂,可能提高筛选的阳性率。     

Marked variation in diazepam sensitivity in Swiss albino mice

Using the righting reflex as the critical level, sleep was measured in Swiss albino mice at a dose of 35 mg/kg diazepam, i.p. Sleep times varied markedly from zero to 120 min with a mean +/- s.d. of 44 +/- 37 (N = 202). The distribution is skewed to the left with a coefficient of skewness of 0.33 +/- 0.17. The sleep times of the two sexes, when analyzed separately, showed similar range, mean and s.d., except that the distribution tended to be more clearly bimodal in males than in females. These animals also exhibited marked variations in their response to either ethanol (4 g/kg) or pentobarbital (45 mg/kg). The diazepam sleep time failed to correlate with the ethanol sleep time. Significant correlation, however, was obtained between diazepam and pentobarbital sleep times. On further analysis with least-squares fit to a straight line, the data yielded a line with a slope of 0.16; thus despite the correlation reaching a significant level, there is no significant difference in the pentobarbital sleep times between mice that have the longest or the shortest diazepam sleep times. By monitoring the plasma and brain levels of diazepam and N-desmethyldiazepam in mice at awakening, it was found that the variations in sleep time cannot be explained by individual differences in drug disposition. The phenomenon is discussed in terms of individual variations in diazepam sensitivity and the possibility of development of tolerance to diazepam almost immediately after diazepam administration.     

Gender-related differences in diazepam effects on performance

In order to investigate the possible differences of diazepam effects in the two sexes, two placebo-controlled double-blind studies were conducted on healthy volunteer students. In one study the subjects received diazepam 10 mg alone or combined with 0.5 g/kg of alcohol in a parallel group design; in the other 0.2 mg/kg of diazepam or placebo were given in a cross-over manner. In both trials diazepam impaired the psychomotor skills of women more than men. The difference was similar in tasks measuring cognitive (digit symbol substitution), motor (balance of extraocular muscles) and sensory (critical flicker fusion) performances. Tapping speed was affected to a similar degree in both genders. Diazepam 10 mg did not cause impairment of body balance, a parameter sensitive to alcohol. The combined effect of diazepam and alcohol was of similar magnitude in both sexes in all objective tests. Subjectively the women felt themselves clumsier than did the men. The calming effect was similar in both groups. The results suggest that while the performance of women may be more vulnerable than men to impairment by diazepam they also are aware of it. The difference of effects is of such magnitude that it may cause bias in experiments unless carefully balanced groups are used.     

Factors modifying the effect of diazepam on plasma corticosterone levels in rats

We have examined factors that alter the effect of diazepam (DZ) on plasma corticosterone (CS) in rats. DZ had a biphasic effect on plasma CS levels: CS decreased with doses below 5 mg/kg and increased with higher doses. Peak response occurred 90 minutes post injection in both sexes. Plasma DZ levels were significantly higher in females than in males and peak at 10 and 30 minutes post injection in males and females, respectively. There was also a sex difference in the pattern of DZ metabolites. An acute stressor (30 minutes of immobilization) did not affect plasma CS levels in rats injected with a 5 mg/kg dose of DZ. Prenatally stressed animals did not differ in basal CS levels or in their response to 5 mg/kg of DZ compared to prenatally non-stressed animals. These two groups of animals also did not differ in plasma levels of DZ or of its metabolites. By contrast, the 5 mg/kg dose of DZ had no effect on plasma testosterone levels in control animals, but increased it in prenatally stressed animals. Furthermore, compared to non-stressed controls, prenatally stressed animals had lower baseline plasma testosterone levels. These results indicate that the effect of DZ on plasma CS is influenced by endogenous as well as exogenous factors and that these effects vary with the particular biochemical parameter under examination.     

Reduction of inflammation in rats by diazepam: tolerance development

High doses of diazepam (10-20 mg/kg) were shown to reduce the volume of acute carrageenan-induced inflammatory paw edema in rats. This effect was not observed after adrenalectomy or long-term use of similar doses of diazepam. The present experiment was undertaken to analyze the effects of long-term (21 daily injections) treatment with diazepam (10 mg/kg) on both carrageenan-induced paw edema (CIPE) and corticosterone serum levels. For comparison, the effects of a single and acute 10 mg/kg dose of diazepam were also analyzed. Results showed that: 1- long-term diazepam treatment induced no changes in CIPE values and corticosterone serum levels; 2- acute diazepam treatment reduced CIPE values and increased corticosterone serum levels; 3- the plasmatic levels of diazepam measured 1 hour after the single treatment or 1 hour after the last dose of long-term diazepam administration were not different. These results indicate the development of tolerance to diazepam effects on both CIPE and corticosterone serum levels and suggest a relevant role for corticosterone on diazepam-induced inhibition of acute inflammation. Data were discussed in the light of peripheral benzodiazepine receptor site (PBR) activation within adrenal gland cells by diazepam, thereby increasing the serum levels of corticosterone and thus reducing CIPE. Possible actions of diazepam on HPA axis activity and/or on cytokine network were also discussed.     

Effect of GABA-negative preparations on the anxiolytic and sedative effects of diazepam

Experiments on rats have shown that bicuculline (2 mg/kg) and picrotoxin (2 mg/kg) abolish the anxiolytic action of diazepam (2.5 mg/kg). Bicuculline (2 and 4 mg/kg) decreases while picrotoxin transforms the sedative effect of diazepam to the anxiolytic one. Picrotoxin (2 mg/kg) reduces the sedative action of gamma-acetylenic GABA (100 mg/kg) but does not favour the manifestation of its anxiolytic effect. It is suggested that the GABA-ergic mechanisms play an important role in the sedative effect of diazepam.     

Regionally specific effects of diazepam on brain serotonin metabolism in rats: Sustained effects following repeated administration

The effects of single (1mg/kg) and repeated (1mg/kg 2¹ daily for 4 days) diazepam administration are investigated on brain regional 5-hydroxytryptamine (5-HT; serotonin) and 5-hydroxy indoleacetic acid (5-HIAA) concentration in rats. Daily treatment decreased food intakes but body weights did not decrease. Administration of diazepam (1mg/kg) to 4 day sahne injected rats on the 5th day decreased 5-HT levels in the hippocampus and increased it in the hypothalamus. 5-HIAA levels were increased in the striatum and decreased in the hypothalamus. 4 day diazepam injected rats injected with sahne on the 5th day also exhibited silmilar changes of 5-HT and 5-HIAA. Cortical levels of 5-HIAA were also smaller in these rats. Administration of diazepam to 4 day diazepam injected rats again decreased 5-HT in the hippocampus and 5-HIAA in the hypothalamus. 5-HT and 5-HIAA were both decreased in the striatum. Regionally specific effects of diazepam on brain serotonin metabolism are discussed in relation to their possible functions.     

Role of the GABA-ergic systems of the brain in manifesting the activating effect of diazepam]

It was shown in experiments on rats that the selective blocker of GABA receptors bicuculline (2 mg/kg) does not decrease the activating effect of diazepam as to the reaction of self-stimulation. The GABA-mimetic muscimol (0.5 and 1 mg/kg) had no effect on self-stimulation rate, while in the dose of 2 mg/kg causing behavioral changes produced a powerful decrease in it (by 93.3%). During the combined administration of diazepam and muscimol (1 mg/kg and 0.5 mg/kg, respectively) no potentiation of diazepam effect was observed. It is suggested that diazepam-induced facilitation of the reaction of self-stimulation is not due to the alteration in the activity of GABA-ergic processes.     

Comparative study of the effect of 3-carboxy-beta-carboline methylamide and diazepam on rat behavior

The effects of benzodiazepine receptor agonist, diazepam, and inverse agonist, FG 7142, were examined. Strong antagonism between FG 7142 (10 mg/kg) and diazepam (1 mg/kg) activity was revealed in the open field test. On the other hand, both FG 7142 and diazepam inhibited isolation-induced intraspecies aggressive behaviour of rats. FG 7142 also reduced interspecies aggression of mouse-killing rats. The findings suggest that both diazepam and FG 7142 have antiaggressive properties in the isolation-induced aggression model, which are mediated by benzodiazepine receptors of the central nervous system.     

Influence of diazepam on regenerating adrenal cortex in Wistar rats

The influence of diazepam on the mitotic activity of regenerating adrenal cortex in male Wistar rats was investigated. Diazepam administration (5 mg/kg/day) was shown to inhibit the mitotic index of adrenocortical cells on the 4th and 8th day after adrenal enucleation combined with contralateral adrenalectomy. The possible mechanism of diazepam action is discussed.     

The effect of a novel pentadecapeptide BPC 157 on development of tolerance and physical dependence following repeated administration of diazepam

A novel gastric pentadecapeptide BPC 157 with different beneficial activities and anticonvulsant effect interacting with GABAergic system could improve diazepam efficacy coadministered (10 microg/kg, 10 ng/kg i.p.) with diazepam (5.0 mg/kg i.p.) twice daily for 10 days, since diazepam chronic medication would otherwise predispose for diazepam- tolerance/withdrawal development (shorter latency to convulsion after convulsant). In diazepam chronically treated mice, it attenuated diazepam tolerance (provoked by later acute administration of diazepam together with convulsant) and postponed physical dependence/withdrawal effects (provoked by later administration of isoniazid). In tolerance assay, at 42 h after the end of conditioning regimen, shorter preconvulsive latencies than in healthy (non-diazepam conditioned) mice following isoniazid (800 mg/kg i.p.) (as hallmark of tolerance) were observed if diazepam (5.0 mg/kg i.p.) was again given acutely to mice previously conditioned with diazepam alone (use of picrotoxin 3.0 mg/kg i.p., as convulsant, with acute application of diazepam in previously diazepam conditioned mice did not lead to tolerance hallmark). This was completely avoided in diazepam+BPC 157 10 microg or diazepam+BPC 157 10 ng chronically treated animals. In physical dependence assay (isoniazid challenge assessed at 6, 14, 42 and 72 h after conditioning medication), when compared to diazepam non-conditioned healthy mice, in diazepam conditioned mice residual anticonvulsive activity was not present already at the earliest post-conditioning interval (i.e., not different latency to isoniazid-convulsions), whereas shorter preconvulsive latencies (as physical dependence/withdrawal hallmark) were noted in diazepam conditioned mice following isoniazid challenge at 42 h and at 72 h after end of conditioning treatment. In diazepam+BPC 157 10 microg- conditioned mice, a residual anticonvulsive activity (i.e., longer latency to isoniazid convulsion) was noted at 6 h post-conditioning, whereas shorter preconvulsive latencies appeared only at 72 h-post-conditioning period. In conclusion, taken together these data (lack of tolerance development (tolerance studies), prolonged residual anticonvulsive activity, and postponed physical dependence/withdrawal hallmark in diazepam+BPC 157 chronically treated mice) with common benzodiazepines tolerance/withdrawal knowledge, it could be speculated that BPC 157 acts favoring the natural homeostasis of the GABA receptor complex as well as enhancing the GABAergic transmission, and having a mechanism at least partly different from those involved in diazepam tolerance/withdrawal, it may be likely used in further therapy of diazepam tolerance and withdrawal.     

Pentazocine and codeine: effects on human performance and mood and interactions with diazepam

Effects of two opioid analgesics on performance and their interactions with diazepam were studied double-blind and cross over in ten healthy students. At two-week intervals the subjects received first a single oral dose of placebo, codeine (100 mg) or pentazocine (75 mg). Then, 1 h 30 min later they were all given diazepam (0.25 mg/kg) orally. Lastly, naloxone (0.4 mg) was injected intravenously at 4 h. In addition to this, the subjects on pentazocine received a second 75 mg dose at 3 h. Codeine and pentazocine alone failed to affect performance in objective tests (body sway, digit symbol substitution, flicker fusion, Maddox wing, nystagmus) recorded at 1 h 30 min. Visual analogue scales showed subjective drug effects: pentazocine made the volunteers talkative, contented, interested and energetic, whilst codeine rendered them mentally slow. 75 mg of pentazocine and 100 mg of codeine produced comparable plasma opiate activity (determined in morphine equivalents) according to radioreceptor bioassay with [3H]-dihydromorphine as a ligand. Impaired performance was clear at the tests done 1.5 and 2.5 h after diazepam. No major interactions were found between opiates and diazepam in objective tests with the exception that nystagmus was stronger after the combined treatment than after diazepam alone. Codeine reduced the absorption of diazepam. Subjectively codeine and pentazocine counteracted the effects of diazepam. The subjects overestimated their performance after opiate + diazepam when compared to diazepam alone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hepatotoxicity of diazepam

Studies of effects of diazepam on liver parenchyma are very scantly. In this study, adult albino rats were treated with diazepam in two different doses (0.25 mg and 0.30 mg/kg body wt) daily for 30 and 60 d. Through light microscopy and electron microscopy, prenecrotic and necrotic changes were noted in the high-dose group. Trace metal analysis indicated that zinc (Zn) was reduced by 30 and 60 day under both the doses, whereas iron (Fe) and copper (Cu) were reduced significantly in these groups only after 60 d of treatment. This reduction in metal contents may have some correlations with necrotic changes in liver parenchyma.