Pharmacological profile of the antidepressant adinazolam, a triazolobenzodiazepine

Adinazolam, which is a 1-dimethylaminomethyl triazolobenzodiazepine, is an effective anxiolytic agent as defined by suppression of stress-induced increases in plasma corticosteroids. Adinazolam is also an effective antagonist of pentylenetetrazole. The 1-dimethylaminoethyl triazolo analog, U-43,465F, was inactive in the stressed rat test and only weakly active against pentylenetetrazole. Adinazolam and U-43,465F have been previously shown to have antidepressant activity in classical screening tests. They have also been found to potentiate the effect of norepinephrine and this is consistent with the activity of the known antidepressants; U-43,465F was found to be equieffective to imipramine in this test. Adinazolam was also effective; however, the magnitude of the potentiation was not as great. The uptake of norepinephrine was only weakly affected by either compound. Potentiation or uptake of serotonin were not significantly-altered pharmacological factors. Receptor binding studies were negative except at the benzodiazepine receptor. Chronic treatment with adinazolam did not decrease the number of beta-adrenergic receptors in the cerebral cortex of the rat, in contrast to the positive effect of imipramine. The discovery of triazolobenzodiazepines with antidepressant activity is of special interest. These agents will hopefully have lower toxicity than the tricyclic antidepressants and thus possess a more favourable therapeutic index. This would be advantageous in the treatment of depression.     

Therapeutic applications of benzodiazepine receptor ligands in anxiety

In this short review, evidence is presented to show that the benzodiazepines produce their variety of pharmacological effects by activating specific receptors that form part of the main inhibitory neurotransmitter receptor system, the γ‐amino‐butyric acid (GABA) system, in the mammalian brain. Different classes of benzodiazepine receptor ligands have been developed which can alleviate anxiety or produce anxiety according to the fine structural changes that occur when the ligands interact with the benzodiazepine receptor. There is some evidence that endogenous substances in the brain can cause either an increase or a reduction in the anxiety state by acting on the benzodiazepine receptor. The unique nature of the benzodiazepine receptor, and the disparate properties of the drugs that act on this receptor, should allow plenty of scope for the development of novel compounds with selective anxiolytic and other properties in the future. Lastly, despite the evidence from animal studies that benzodiazepine receptor function changes in response to drug treatment, there is little evidence from human brain studies that such changes are relevant to the phenomena of tolerance, dependence and withdrawal effects that have been the recent cause for public concern. Copyright © 1999 John Wiley & Sons, Ltd.     

Effects of chlordiazepoxide,buspirone, and serotonin receptor agonists and antagonists on responses of squirrel monkeys maintained under second-order schedules of intramuscular cocaine injection or food presentation

Lever pressing of squirrel monkeys was maintained under second-order schedules of either food presentation or cocaine injection. The first response after 3 min produced a 2 sec change in the color of a visual stimulus; the tenth stimulus presentation was followed by either an i.m. injection of cocaine (0.3, 1.0, or 2.0 mg/kg) or the delivery of food. The benzodiazepine chlordiazepoxide (0.3-5.6 mg/kg) increased responding maintained by food at doses that decreased cocaine-maintained responding. In contrast, buspirone, a novel nonbenzodiazepine anxiolytic (0.001-0.03 mg/kg), its analog gepirone (0.003-0.03 mg/kg), and the N serotonin 1A (5-HT_1A) agonist 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT; 0.0003-0.001 mg/kg) increased cocaine-maintained responding at doses that decreased responding maintained by food. The inverse agonist at benzodiazepine receptors β-carboline-3-carboxylic acid ethyl ester (βCCE) only decreased response rates irrespective of the maintaining event. m-Chlorophenylpiperazine (mCPP), an agonist at 5-HT_1b receptors, increased responding maintained by food while only decreasing cocaine maitained responding (0.001-0.03 mg/kg), whereas metergoline (0.1-0.3 mg/kg), a serotonin antagonist with affinity for both 5-HT₁ and 5-HT₂ receptors, produced large response rate increases in both groups of monkeys. Administration of the 5-HT₂ antagonist ketanserin (0.03-3.0 mg/kg), the 5-HT_1A compound spiroxatrine (0.0003-0.03 mg/kg), or the nonselective 5-HT agonist quipazine (0.003-1.0 mg/kg) resulted in dose-dependent response rate decreases in both groups. These results further differentiate buspirone and related compounds from typical anxiolytics and suggest a differential involvement of 5-HTIA receptors in behaviors maintained by cocaine or food presentation.     

Effects of flurazepam on amino acid-evoked responses recorded from the lobster muscle and the frog spinal cord.

The effects of flurazepam hydrochloride on GABA- or glutamate-evoked responses recorded from the lobster muscle fibre and the frog isolated spinal cord were studied using electrophysiological techniques. On lobster muscle flurazepam (up to 100 μM) reversibly antagonized responses to bath-applied or iontophoretically-applied glutamate without any effect on GABA responses. Higher concentrations of flurazepam (>200 μM) sometimes increased the resting membrane conductance, an effect different from that of GABA in being insensitive to picrotoxin (0.5 μM). In the tetrodotoxin (TTX)-treated frog spinal cord flurazepam (5 μM) reversibly antagonized both glutamate- and GABA-evoked dorsal root depolarizations although a smaller dose (2.5 μM) clearly potentiated the action of GABA. Spontaneous fluctuations of the dorsal root d.c. level in the presence of flurazepam were also observed. It is suggested that flurazepam antagonized amino acid responses by blocking receptor-activated Na⁺ channels on the postsynaptic membranes. However, the potentiation of GABA action on the frog spinal cord may have involved either release of endogenous GABA or “sensitization” of spinal receptors to GABA, an action easily obscured by the predominant antagonistic effect of flurazepam at higher concentrations.     

Effects of combinations of methylxanthines and adenosine analogs on locomotor activity in control and chronic caffeine-treated mice

Chronic caffeine ingestion (CCI) by male NIH Swiss strain mice results in a prolonged reduction in locomotor activity and alterations in response to caffeine, other xanthines, and adenosine analogs. Caffeine, the A₁ selective 8-cyclopentyltheophylline (CPT), and the A₂-selective 3,7-dimethyl-1-propargylxanthine (DMPX) remain stimulatory and the bell-shaped locomotor dose-response curves are left-shifted after CCI. The depressant effects of methylxanthines that are potent phosphodiesterase inhibitors remain after CCI. After CCI, mice became more sensitive to depressant effects of A₁, mixed A₁/A₂, and A₂ agonists. In the presence of caffeine the A₁-selective agonist N⁶-cyclohexyladenosine (CHA), the mixed A₁/A₂ agonist 5′-N-ethylcarboxamidoadenosine and the A₂-selective agonist 2-[(2-aminoethylamino)-carbonylethylphenylethylamino]-5′-N-ethylcarboxamidoadenosine (APEC) all have dose-response curves, appearing to consist of initial depressant effects, then stimulatory effects, and finally pronounced depressant effects. The phasic character is reduced or absent after CCI. Synergistic depressant effects of combinations of CHA and APEC also appear reduced after CCI. © 1993 wiley-Liss, Inc.     

Restoration of shock-suppressed behavior by treatment with (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5, 10-imine (MK-801), a substance with potent anticonvulsant,central sympathomimetic,and apparent anxiolytic properties

MK-801 was evaluated in rats for “antipunishment” and “anticonflict” activity in two procedures: (1) A conditioned emotional response (CER) test involving the suppression of lever-pressing by unaviodable shock and (2) a simple conflict test in water-deprived animals that were shocked for licking water. The effect of MK-801 in both procedures was qualitatively similar to the benzodiazepines. Lever-pressing in the CER test was increased by MK-801 at doses ranging from 50–400 μg/kg administered orally (p.o.) at either 0.5 or 2 hours prior to testing. The number of shocks received in the “thirsty rat” conflict procedure was increased by MK-801 at doses from 110–1,000 μg/kg p.o., providing the compound was given 2 or more hours before test. MK-801 was without anticonflict activity when administered 1 hour prior to study. In squirrel monkeys trained in a response-contingent conflict paradigm, a specific anticonflict effect for MK-801 (50–400 μ/kg p.o.) was not demonstrable. As assessed by observing the overt behavior of squirrel monkeys, MK-801 at doses greater than 100 μg/kg p.o. caused apparent “taming” or “tranquilization.” Chlordizepoxide and diazepam given, respectively, at doses above 1 and 2 mg/kg p.o. had a similar “taming” action. The benzodiazepines possessed a greater separation between doses producing “taming” and those causing ataxia than did MK-801. The mode of action for the antipunishment effect of MK-801 in rats is not known, but it was found that naloxone (2 or 5 mg/kg SC) antagonized the anticonflict actions of both MK-801 and chlordiazepoxide. In vitro, MK-801 was inactive (IC₅₀ > 2 μM) with respect to competing for binding to rat brain tissue by various radioligands (diazepam, muscimol, apomorphine, spiroperidol, serotonin, LSD, WB-4101, dihydroalprenolol, QNB, and 2-chloroadenosine). An increase in ³H-diazepam binding in vitro in rat brain tissue was detected following acute, but not chronic, treatment in vivo with MK-801.     

Use of benzodiazepines and benzodiazepine-related drugs in the Nordic countries between 2000 and 2020

Use of benzodiazepines (BZ) and related drugs is subject to considerable debate due to problems with dependency and adverse events. We aimed to describe and compare their use across the Nordic countries. Data on the use of clonazepam, BZ-sedatives, BZ-hypnotics, and benzodiazepine-related drugs (BZRD) in adults (≥20 years) were obtained from nationwide registers in Denmark, Finland, Iceland, Norway, and Sweden, 2000–2020. Main measures were therapeutic intensity (TI:DDD/1000 inhabitants [inhab.]/day) and annual prevalence (users/1000 inhab./year). Overall, TI of BZ and related drugs decreased in all Nordic countries from 2004 to 2020. However, there were considerable differences between countries in TI. In 2020, the TI of BZ and related drugs ranged from 17 DDD/1000 inhab./day in Denmark to 93 DDD/1000 inhab./day in Iceland. BZRD accounted for 55–78% of BZ use in 2020, followed by BZ sedatives at 20–44%, BZ-hypnotics at <1–5%, and clonazepam at <1–2%. Annual prevalence of BZ use increased with age in all countries, and the highest annual prevalence was observed among people ≥80 years. Overall, the use of BZ and related drugs has decreased in all Nordic countries from 2004 to 2020, however, with considerable differences in their use between countries. The highest prevalence was observed among the oldest age groups—despite warnings against their use in this population.     

Occupation of brain receptors by benzodiazepines and β-carbolines: Multiple mechanisms and responses

High affinity for the brain benzodiazepine receptor can no longer be considered predictive of benzodiazepine-like pharmacology in vivo. Studies of ³H-diazepam (³H-DZ) and ³H-propyl-β-carboline-3-carboxylate (³H-PrCC) binding were performed to investigate how occupation of the benzodiazepine receptor by these two high-affinity ligands leads to their significantly different pharmacological effects. In mouse hypothalamus, there are four times as many ³H-DZ binding sites as ³H-PrCC binding sites (B_max values = 1,025 and 265 fmol/mg protein, respectively) and both types of site form a distinct anterior-to-posterior gradient in this tissue. Physiological Ca⁺² concentrations do not regulate ³H-ligand binding in Ca⁺²-depleted whole mouse brain membranes, but in the presence of increasing concentrations of guanosine 5′-triphosphate (GTP), Ca⁺² stimulates ³H-DZ binding up to 25%. In contrast, ³H-PrCC binding is unaffected by Ca⁺² and GTP. Diazepam (DZ) and ethyl β-carboline-3-carboxylate (βCCE) both stimulate ³H-muscimol binding to GABA receptors in whole mouse brain membranes (DZ = +57%, βCCE = +27%), and βCCE partially blocks the effect of the benzodiazepine. Moreover, alkyl β-carboline-3-carboxylates prevent a temperature-induced thermodynamic transition in the benzodiazepine receptor that occurs in the presence of GABA. Studies of 8-anilino-1-naphthalene sulfonic acid fluorescence (ANS) perturbation have also suggested that occupation of the receptor by a benzodiazepine results in a conformational change. Although benzodiazepines and β-carbolines are high-affinity ligands for the benzodiazepine receptor, these results suggest that their different pharmacological profiles may result from significant differences in binding mechanisms and receptor responses.     

The activity of cis and trans -2- (aminomethyl) cyclopropane carboxylic acids on gaba — related mechanisms in the central nervous system of limulus and periplanata and of mammals

Some pharmacological actions of (±) — cis — and (±) — trans -2-(aminomethyl) cyclopropane carboxylic acids, conformationally restricted analogues of GABA, are described. The trans isomer (TAMP) was 17 and 4.5 times less active than GABA in hyperpolarising central neurones of Limulus and Periplanata and 10.8 times less active in displacing [³H]-muscimol from rat brain membranes. The cis isomer (CAMP) was ineffective on Limulusneurones at 35 μmoles, 650 times less active on Periplanata neurones and only weakly displaced [³H]-muscimol at 100 μm. Neither isomer inhibited synaptosomal uptake of [³H]-GABA at 100 μM. These data suggest that the invertebrate receptors studied respond to GABA in an extended conformation.     

Inosine and N6-substituted adenosine analogs lack anxiolytic activity in the pentylenetetrazol discrimination model of anxiety

Although some in vitro studies have raised the possibility that endogenous purines mediate the therapeutic effects of the benzodiazepines, no behavioral studies have been performed to confirm or reject this hypothesis. Consequently, inosine and the adenosine A1 receptor agonists N6- (L-phenylisopropyl) adenosine (L-PIA) and 2-chloroadenosine (2CA) were evaluated for diazepam-like anxiolytic activity in the pentylenetrazol-saline discrimination model of anxiety. Rats were trained to press one of two levers for food reward after pentylenetetrazol (PTZ) injection (20 mg/kg) and to press the other after saline injection. During testing in these rats, diazepam (10 mg/kg) blocked the PTZ-induced selection of the PTZ-appropriate lever (i.e., rats selected the saline-correct lever). Inosine, L-PIA, and 2CA neither blocked selection of the PTZ-appropriate lever after PTZ administration nor did they reverse the diazepam blockade. It is suggested that adenosine or inosine may not act endogenously to mediate the anxiolytic effects of benzodiazepines.     

Modification of GABA-mediated depolarization of the cat ganglion by pentobarbital and two benzodiazepines.

The effect of pentobarbital and two benzodiazepines, flurazepam and midazolam (Ro 21-3981), on GABA-mediated depolarization, was assessed on the superior cervical ganglion of the cat. Intra-arterial injection of pentobarbital at a low concentration (100 nM) prolonged and increased the negative potential evoked by GABA. At higher concentrations (300 nM-1μM), pentobarbital mimicked the action of GABA by depolarizing the ganglion. This effect was blocked by picrotoxin and bicuculline. The benzodiazepines, in smaller doses, potentiated GABA-mediated depolarization. After administration of larger doses the enhancement of depolarization was preceded by antagonism of GABA-induced depolarization. It is concluded that both pentobarbital and the benzodiazepines enhance GABA activity, at least in part, through a mechanism independent of a presynaptic site of action.     

Effects of diazepam and picrotoxin on hyponeophagia in rats

The effects of diazepam (1 mg/kg), picrotoxin (1.5 mg/kgmg/kg) and both treatments on hyponeophagia in male and female rats were studied. Diazepam reduced eating latency and enhanced the total amount eaten in the test. Picrotoxin increased approach and eating latencies and reduced amount eaten, females being more sensitive to these actions. Behavioural sensitivity to diazepam was reduced by picrotoxin for approach latency but enhanced for eating latency. These findings are discussed in connection with the GABA hypothesis of the actions of benzodiazepines.     

鞘内注射荷包牡丹碱和L-烯丙基甘氨酸对氯胺酮脊髓镇痛的影响

目的　在体研究脊髓GABAA 受体和氯胺酮(Ket)脊髓镇痛的关系 ,并初步探讨突触前、后机制在其中的作用。方法　用热水甩尾法和醋酸扭体法 ,观察鞘内注射 (ith)Ket(2 5 ,5 0 ,10 0 μg)对小鼠痛阈的影响。并用热水甩尾法观察GABAA 受体拮抗剂荷包牡丹碱 (Bic ,0 .0 5 ,0 .1,0 .2 μg ,ith) ,GABA合成酶抑制剂L 烯丙基甘氨酸 (AG ,2 0 0mg·kg- 1,ip)及两药合用对小鼠基础痛阈和Ket(10 0 μg ,ith)脊髓镇痛的影响。结果　Ket可产生剂量依赖性的镇痛作用。Bicith对小鼠痛阈无明显影响 ,但可明显减弱Ket的脊髓镇痛作用。ipAG或合用Bic(0 .0 5 ,0 .1μg,ith)对小鼠痛阈都无明显影响 ,而预先AGip可明显减弱Ket脊髓镇痛作用 ;且AGip后 ,Bic(0 .1μg ,ith)对Ket脊髓镇痛无明显拮抗作用。 结论　脊髓是Ket的镇痛部位之一 ,Ket的镇痛作用可能和Ket促进脊髓释放GABA有关。     

The modulation of cortical acetylcholine release by GABA, GABA-like drugs and benzodiazepines in freely moving guinea-pigs

In order to define the modulatory role played by gamma-aminobutyric acid (GABA) in corticopetal cholinergic projections, the effect of this amino acid and related drugs on gross behaviour, the EEG and the release of acetylcholine (ACh) from the cerebral cortex in freely moving guinea-pigs was studied. gamma Aminobutyric acid, injected intracerebroventricularly (20-50 mumol) induced a three-phase picture: first (5-15 min) behavioural activation and increased release of ACh, then (30-90 min) depression, EEG synchronization and reduced release of ACh, and finally "rebound" stimulation. Ethanolamine-O-sulphate (EOS) injected intraventricularly (28 mumol/kg) or intraperitoneally (14 mmol/kg) reproduced the first two phases of the effects of GABA (i.e. stimulation followed by inhibition), while diazepam (0.7 and 3.5 mumol/kg, i.p.) and flurazepam (32 mumol/kg, i.p.) caused, at first, only depression. Muscimol and 4,5,6,7-tetrahydroisoxazolo(4,5-c)pyridine-3-ol (THIP) injected intraventricularly (in the nmol range) or intraperitoneally (in the mumol range) produced behavioural activation and increased release of ACh; the depressant signs appeared only after very large, toxic doses. Picrotoxin and bicuculline, at sub-convulsive doses, reduced the symptomatology caused by GABA and antagonized the sedation produced by diazepam. Methysergide (8-16 mumol/kg, i.p.) prevented the behavioural activation and the increased release of ACh by GABA, unmasked the depression due to subthreshold doses of diazepam (i.c.v., 7-70 nmol) and reversed the stimulation induced by muscimol into sedation and reduced the outflow of ACh. Pretreatment with 5,7-HT also dampened and shortened the stimulation by muscimol.(ABSTRACT TRUNCATED AT 250 WORDS)     

二巯丙磺钠对四次甲基二砜四胺拮抗GABA受体的影响(英文)

AIM: To study effects of sodium dimercaptopropanesulfonate (DMPS) on the antagonism of tetramethylenedisulphotetramine (TETS) to gamma-aminobutyric acid (GABA) receptor. METHODS: Acute toxicity experiments were conducted to observe the effects of DMPS and TETS on mice. Contents of free amino acids in mouse brain were determined with automatic analyzer for amino acids. Autoradiography was used to observe the [3H]GABA bindings in the rat brain slices under different conditions. RESULTS: After icv and ip DMPS, the number of mice experiencing convulsions reduced from 20 in control group to 4 and 2 respectively in TETS poisoned mice. The content of GABA was altered in DMPS control group and TETS control group compared with DMPS protection group and NS control group [micromol/g: (2.09 +/- 0.05) and (2.67 +/- 0.15) vs (2.40 +/- 0.10 (micromol/g)) and (2.41 +/- 0.21)]; the content of glutamic acid was (12.3 +/- 1.2), (12.0 +/- 0.8), (10.2 +/- 0.6), and (11.8 +/- 1.0) micromol/g in NS control group, DMPS control group, TETS control group, and DMPS protection group, respectively. The OD value of autoradiograms decreased in TETS group compared with buffer control group in cortex, hippocampus, diencephalon, and brainstem [(0.084 +/- 0.008), (0.081 +/- 0.009), (0.094 +/- 0.006) and (0.081 +/- 0.006), vs (0.102 +/- 0.003), (0.109 +/- 0.005), (0.128 +/- 0.007), and (0.125 +/- 0.008), respectively]. OD value was maintained or higher than the normal level in DMPS+TETS group in the four brain areas [(0.116 +/- 0.008), (0.125 +/- 0.011), (0.129 +/- 0.005), and (0.128 +/- 0.010) vs (0.102 +/- 0.003), (0.109 +/- 0.005), (0.128 +/- 0.007), and (0.125 +/- 0.008), respectively]. CONCLUSION: The inhibitory effects of DMPS on the antagonism of TETS to GABA receptor are due to the increase in the GABA binding to its receptors in brain caused by DMPS     

Effects of chlordiazepoxide and of valproate on hyponeophagia in rats. Evidence for a mutual antagonism between their anxiolytic properties

The effects of chlordiazepoxide (0,2.5 and 7.5 mg/kg), of valproate (0,100 and 300 mg/kg), and of combinations of these drugs, on hyponeophagia in rats, were studied using a food preference test. Chlordiazepoxide alone reduced the latency for eating, and also enhanced the time of eating and the amount of familiar food eaten at the smaller dose, and of novel food eaten at the larger dose. Valproate alone reduced the latency of eating and enhanced time of eating and the amount of novel food eaten, especially at 300 mg/kg. However, valproate antagonised the effects of chlordiazepoxide on all behavioural measures. These findings are discussed in the context of the GABA hypothesis of the actions of benzodiazepines, with the conclusion that valproate has an atypical pharmacological profile amongst putative GABA agonists, and may have partial agonist activity at the proposed benzodiazepine/GABA receptor complex.