Effects of chlordiazepoxide on passive avoidance responses in rats

The effect of chlordiazepoxide on the retention of a passive avoidance response was determined in rats. Chlordiazepoxide or saline was given before testing in a two compartment passive avoidance response (PAR) apparatus or in an open field, and again after 48 and 72 h.The PAR was usually depressed by chlordiazepoxide (CDP) given during acquisition, and it remained present after 48 and 72 h. Treatment with chlordiazepoxide before the second and third testing abolished the depression of PAR. CDP had most effect on the acquired PAR.Shock treatment resulted in an increase in defecation and urination and a decrease in ambulation and rearing in the PAR apparatus as well as in the open field. These effects were reduced by CDP, irrespective of drug-state changes. A clear-cut reduction in defecation and urination under CDP in well-habituated home cages was also seen. The depressant effect of CDP upon the PAR is discussed in relation to the drug's inhibitory action upon the hippocampal theta activity.     

A comparison of the effects of vasopressin and oxytocin with amphetamine and chlordiazepoxide on passive avoidance behaviour in rats

On the basis of results obtained from passive avoidance studies, we have argued that the neuropeptide vasopressin could act on arousal, rather than memory processes in rats (Sahgal et al. 1982). In this report, we examine the effects of substances that are known to increase (d-amphetamine) or decrease (chlordiazepoxide) behavioural arousal, and compare the data with those obtained after vasopressin or oxytocin treatment. All four substances yielded broadly similar bimodal results (although the oxytocin data failed to reach significance). We argue for an arousal interpretation which suggests that performance and arousal are related in an inverted-U manner. The data also indicate that care must be taken in selecting appropriate statistical tests.     

Injections of atropine into the caudate nucleus impair the acquisition and the maintenance of passive avoidance

Two experiments were performed to test the hypotheses that cholinergic activity of the caudate nucleus (CN) is involved in the acquisition and in the maintenance of passive avoidance behavior. Rats were trained, in one trial, to avoid one of two compartments of a conditioning box and retention of the task was measured 24 hours later. Several doses of atropine were injected into the CN of independent groups of animals. In Experiment 1 the atropine was injected 2 minutes after training and in Experiment 2 it was injected 6 minutes before retention testing. In both cases a dose-dependent retention deficit was found. These results indicate that striatal cholinergic activity is indeed involved in the processes that mediate passive avoidance conditioning.     

Facilitating effects of chlordiazepoxide on the performance of mice in an inhibitory avoidance task

Inhibitory avoidance behaviour of mice was studied by using an automated procedure. Animals were subjected to five 15-min sessions. Facilitation of the inhibitory avoidance behaviour was observed following the administration of chlordiazepoxide at doses which did not produce significant effects on spontaneous locomotor activity.     

Involvement of GABAergic systems in benzodiazepine-induced impairment of passive avoidance learning in mice

The possible involvement of GABAergic neuronal systems in benzodiazepine(BZP)-induced impairment of a passive avoidance response was investigated. Chlordiazepoxide(CDP) impaired passive avoidance when administered prior to training. The CDP-induced impairment was antagonized by pretreatment with picrotoxin, but not by pretreatment with bicuculline or posttraining administration of picrotoxin. On the contrary, when combined with muscimol, the dose at which CDP impaired the response was lower than the dose at which it did so alone. The synergy of muscimol and CDP was attenuated by pretreatment with flumazenil or bicuculline. From these results, we conclude that GABAergic systems play an important role in the BZP-induced impairment of passive avoidance.     

The comparative effects of benzodiazepines,progabide and PK 9084 on acquisition of passive avoidance in mice

Acquisition of passive avoidance following aversive conditioning to a dark compartment was measured in mice under the influence of one of seven bezodiazepines, the GABA-mimetic drug progabide or PK 9084, a nonbenzodiazepine ligand on benzodiazepine receptors.The drugs were administered prior to the training trial and retention was measured in the absence of the drug 24 h later. Oral administration (dose in mg/kg in parentheses) of flunitrazepam (0.1), lorazepam (1.0), nitrazepam (3.0), diazepam (10), flurazepam (10) and chlordiazepoxide (30), all prevented retention whereas progabide (100–800) and PPK 9084 (10–100) were ineffective. In comparison to effects on motor capacity none of the benzodiazepines was outstanding in its acquisition interfering effects.     

The effect of para-chlorophenylalanine and scopolamine on passive avoidance in chicks

Four-day-old Vantress x Arbor Acre chicks were treated for key-peck passive avoidance (PA) learning following intraperitoneal injections of parachlorophenylalanine (PCPA) and/or scopolamine. In Experiment 1, chicks were pre-treated with either three or five injections of PCPA (150 mg/kg) or saline across th first three posthatch days and then tested for PA learning on the fourth posthatch day. In Experiment 2, chicks were first pre-treated with three injections of PCPA (150 mg/kg) or saline, and then injected with either scopolamine (0.5 mg/kg) or saline 20 min prior to PA testing on the fourth posthatch day. Major findings were: (a) Chicks pre-treated with PCPA did not significantly differ from saline control chicks in either the acquisition or maintenance of response suppression during PA testing; (b) chicks injected with scopolamine were significantly disrupted in PA learning as compared to saline control chicks; and (c) PCPA pre-treatment did not significantly affect the scopolamine-induced disruption of PA learning. These findings, therefore, suggest that cholinergic, but not serotonergic, mechanisms are involved in PA learning of the young chick.     

Enhancement by secoverine and physostigmine of retention of passive avoidance response in mice

A one-trial passive avoidance test in the mouse, in which drugs were injected intraperitoneally immediately after the shocked acquisition trial, was used. The effects of enhancing central cholinergic transmission on retention of passive avoidance was investigated using secoverine, which blocks muscarinic autoreceptor-mediated inhibition of acetylcholine release, and using physostigmine, an acetylcholinesterase inhibitor. Secoverine (1.0–5.0 mg/kg) and physostigmine (0.1–0.4 mg/kg) were found to improve retention of the avoidance response measured 24 h after acquisition. These effects were augmented when the two drugs were given in combination. In contrast, atropine (5.0 mg/kg) tended to impair retention of passive avoidance and blocked the facilitatory effects of physostigmine. The results support the hypothesis of a novel approach to treatment of memory disorders based on blockade of muscarinic autoreceptors, to augment central cholinergic activity.     

The effects of clozapine on shuttle-box avoidance responding in rats: comparisons with haloperidol and chlordiazepoxide

Previous studies have shown that clozapine produces effects different from those of other antipsychotic drugs on positively reinforced responding but may give rise to similar disruptions of avoidance behavior. To investigate the actions of clozapine on avoidance responding in more detail the effects of this drug were compared with those of haloperidol and chlordiazepoxide in rats trained to avoid shock in a shuttle-box. Acute administration of all three drugs reduced avoidance responses and increased escape failures although clozapine produced this latter effect only at a high dose. With repeated administration of each drug over 4 days tolerance developed rapidly to the effect of clozapine, the effect of haloperidol increased and there was no systematic change in the action of chlordiazepoxide. Disrupted avoidance responding after acute administration of clozapine does not reflect the clinical antipsychotic action of this drug.     

Double dissociation between the effects of muscarinic antagonists and benzodiazepine receptor agonists on the acquisition and retention of passive avoidance

Both muscarinic antagonists, such as scopolamine, and benzodiazepine receptor (BZR) agonists, such as diazepam, produce a reliable impairment in the performance of one trial passive avoidance. Such deficits are frequently interpreted as drug-induced amnesia. However, these deficits could also result from a learning impairment. The present experiments compared the effects of two BZR agonists, lorazepam (0, 0.125, 0.25, and 0.375 mg/kg, IP) and diazepam (0, 0.78, 1.56, and 3.13 mg/kg, IP) with the effects of two muscarinic antagonists, scopolamine (0, 0.6, 0.8 and 1.0 mg/kg, SC) and atropine (0, 15, 30 and 60 mg/kg, IP) on a multiple trial passive avoidance task. In this procedure, the rats were trained with a 5-min inter-trial interval until a learning criterion was achieved. Retention was assessed 24 h later. This enabled the effects of the drugs on the acquisition and the retention of a passive avoidance response to be dissociated. Both atropine and scopolamine produced a marked impairment in the acquisition of the passive avoidance response, but did not impair retention. In contrast, diazepam and lorazepam did not alter the acquisition of a passive avoidance response, but did produce a dose-dependent impairment of retention. These results therefore demonstrate a double dissociation between the effects of muscarinic antagonists and BZR agonists on the acquisition and retention of passive avoidance.     

Clozapine and olanzapine exhibit an intrinsic anxiolytic property in two conditioned fear paradigms: contrast with haloperidol and chlordiazepoxide

Psychotic fear and anxiety disturbances are seen at a relatively high frequency in patients with schizophrenia. Atypical anti-psychotics are believed to show superior efficacy in reducing these symptoms. However, clinical and preclinical evidence regarding their anxiolytic efficacy has been mixed. In this study, we evaluated the possible anxiolytic property of two atypicals clozapine and olanzapine and compared them with typical haloperidol and chlordiazepoxide (a prototype of sedative-anxiolytic drug) in two preclinical models of fear. In Experiment 1, we used a fear-induced passive avoidance and conditioned place aversion paradigm and examined the effects of clozapine (20 mg/kg, sc), haloperidol (0.05 mg/kg, sc) and chlordiazepoxide (10 mg/kg, ip). In Experiments 2 and 3, we used a two-way active avoidance conditioning paradigm and further compared the effects of clozapine (20 mg/kg, sc), haloperidol (0.05 mg/kg, sc), chlordiazepoxide (10 mg/kg, ip) and three doses of olanzapine (0.5, 1.0, and 2.0 mg/kg, sc). Results show that clozapine and chlordiazepoxide, but not haloperidol, significantly attenuated the shock conditioning-induced place aversion, decreased the amount of defecations and the number of the 22-kHz vocalizations. Clozapine also reduced the shock conditioning-induced hyperthermia. Similar to clozapine, olanzapine also significantly decreased the amount of defecations and reduced the shock conditioning-induced hyperthermia, but it did not inhibit the 22-kHz vocalizations. This study demonstrates that clozapine and olanzapine possess an intrinsic anxiolytic property, which is not attributable to its superior anti-“psychotic” effect or its favorable effects on motor functions or learning and memory processes. These findings also suggest that the combined use of passive avoidance and active avoidance conditioning models can be useful in better differentiating typical and atypical anti-psychotics as well as anxiolytics.     

Some analogs of Tyr-MIF-1 affect passive avoidance behavior but not motor activity in rats

The effects of three analogs of the brain peptide Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) were tested in several behavioral tests after peripheral injection in rats. In the passive avoidance test, rats injected SC with 1 mg/kg Ala-MIF-1 or Phe-MIF-1 entered the second compartment of two-chamber shuttle box significantly faster than did rats receiving diluent. Leu-MIF-1 failed to produce significantly faster entry compared to diluent. None of the peptides significantly affected ambulation, rearing, or defecation. Flinch and escape thresholds were not affected by Ala-MIF-1, the only analog tested for this behavior. The results demonstrate that some analogs of Tyr-MIF-1 can exert behavioral effects similar to those exerted by the parent compound whereas other analogs resemble MIF-1 in being inactive under these experimental conditions.     

Strain differences in the effects of chlorpromazine and chlordiazepoxide upon active and passive avoidance in mice

Summary Four inbred strains of mice were compared on an active and a passive avoidance task in a two-compartment cage. Active mice were trained to cross frequently between compartments to avoid shock; passive mice were shocked for crossing. Yoked controls in both procedures received shocks at the same time as experimentals. Strains learning the active task well did poorly in the passive task; strains poor in active learning were superior on the passive task. The results support the view that strain differences in avoidance learning are more related to variations in strength of a kinetic drive than to strength of fear. Chlordiazepoxide affected crossings similarly in actively and passively trained Ss; chlorpromazine reduced crossings in actively trained and increased crossings in passively trained Ss. This result is consistent with dual motivational systems differentially susceptible to alteration by administration of drugs. Chlordiazepoxide acts primarily upon kinetic drive; chlorpromazine upon fear.This investigation was supported in part by United States Public Health Service Research Grants MH-01775 and MH-11327 from the National Institute of Mental Health.The author acknowledges the technical assistance of Frank Clark and Jane Harris.The principles of laboratory animal care as promulgated by the American Psychological Association were observed in this study.     

The effects of chlordiazepoxide HCl administration upon punishment and conditioned suppression in the rat

Rats were trained to lever press for sucrose on a random interval (RI) 64-s schedule. During a 55 min session there were four 3 min intrusion periods signalled by a flashing house-light. In experiment 1 there were two groups matched for baseline response rate. During the intrusion periods one group received response-independent footshock on an independent RI64 schedule; the other group received responsecontingent shock on this schedule. Shock intensity was varied for each rat to match degree of response suppression between the two groups. Chlordiazepoxide HCl (CDP) in doses 0.5–5 mg/kg alleviated response suppression equally in both groups. Experiment II followed the same procedure, except that all animals had the same shock intensity, producing greater response suppression in the response-contingent shock groups. CDP alleviated response suppression more in the response-contingent shock groups, significantly so at 5 mg/kg, nonsignificantly at 1 mg/kg. These results suggest that previous reports that CDP differentially alleviates the response suppression produced by response-contingent shock are an artefact of rate dependency.     

Luteinizing-hormone-releasing hormone modifies retention of passive and active avoidance responses in rats

The influence of posttraining subcutaneous administration of luteinizing-hormone-releasing hormone (LHRH) was tested on the retention of either active or passive avoidance conditioning in male rats. Injection of LHRH (200/kg) immediately after the acquisition of an active avoidance response (two-way shuttle behavior) enhanced retention of the response, assessed 7 days later. When the neuropeptide was injected immediately after a passive avoidance conditioning training, the effects varied with the intensity of the footshock applied. LHRH enhanced retention of avoidance training with weak footshock (0.20 and 0.35 mA) but impaired retention of training with strong footshock (0.70 and 1.0 mA). The effects of LHRH seem to be unspecific since they are similar to those observed after treatment with several hormones. The results are discussed based on the interactions between peripherally injected hormones and endogenous substances released following footshock. A modulatory effect on the monoaminergic pathway involved in memory storage processes is postulated.     

GABAergic modulation of memory with regard to passive avoidance and conditioned suppression tasks in mice

The role of GABAergic neuronal system in learning and memory was investigated using the step-down typed passive avoidance and rapidly learned conditioned suppression tasks in mice. GABA antagonists, picrotoxin and bicuculline, or a GABA synthesis inhibitor, 3-mercaptopropionic acid (3-MP), were administered just after the training test. All of these drugs caused amnesia: they shortened the step-down latency (SDL) and attenuated the conditioned suppression of motility in the retention test conducted 24 h after the administration. Furthermore, we investigated the effect of GABA receptor agonists, muscimol and baclofen, or a GABA transaminase inhibitor, aminooxyacetic acid (AOAA), on these amnesia models. GABA agonists showed an antiamnesic action as follows: in the passive avoidance task, 1) picrotoxin-induced amnesia was antagonized by muscimol, baclofen and AOAA. 2) Bicuculline-induced amnesia was antagonized by muscimol and AOAA but not by baclofen. 3) 3-MP-induced amnesia was antagonized only by muscimol. 4) In the rapidly learned conditioned suppression task, picrotoxin-, bicuculline- and 3-MP-induced amnesia were antagonized by muscimol, baclofen and AOAA. These results suggest that the GABAergic neuronal system plays an important role in the memory retention of passive avoidance and rapidly learned conditioned suppression tasks.     

Effects of antimuscarinic cholinergic drugs injected systemically or into the hippocampo-entorhinal area upon passive avoidance learning in young rats

Passive avoidance learning was significantly impaired by atropine (5 mg/kg, IP) or scopolamine (0.5 mg/kg), but not by methyl-atropine (5 mg/kg) or methyl-scopolamine (0.5 mg/kg), from postnatal day 15 on. In contrast, an improvement was observed, not significant at 11 days and significant at 13 days, probably due to nonspecific effects. Retention of the response increased from 6 h at 13 days, to 24 h at 17 days. In treated rats, retention was abolished at 13 and 15 days, and impaired at 17 and 20 days. Acquisition of the response was also significantly impaired by bilateral injections of atropine (1, 5, and 20 g) into the posteroventral hippocampo-entorhinal (VHE) area, from day 15 on. Concomitantly, extinction was accelerated. At 14 days, atropine had no influence. At 13 days, a facilitatory action was observed, with better acquisition and greater resistance to extinction, possibly linked to affective changes. The results conform that central muscarinic cholinergic mechanisms are involved in passive avoidance learning from postnatal day 15 on, and demonstrate that some pathways of this system are located in the VHE area, become efficient at 15 days, and improve markedly between 17 and 18 days.     

Changes in the amnesic and aversive properties of avoidance conditioning with chlordiazepoxide

In two series of experiments the effects were investigated of chlordiazepoxide (CDP) upon acquisition of avoidance behavior in mice using footshock to establish an avoidance response and posttrial electroconvulsive shock (ECS) to retroactively disrupt the retention of that response. The relationship of either footshock and/or ECS during passive avoidance conditioning acquisition following prior drug treatment provided for reduced active avoidance response acquisition where such training was given following assessment of the retention of the passive avoidance behavior. The present experiments suggest that chlordiazepoxide interacts with acquired avoidance behavior such as to modify the amnesic properties of ECS. This may be due to a partial antagonism of the ECS induced retrograde amnesia, or to modification of active avoidance acquisition by drug treatment.     

Effects of scopolamine,physostigmine and chlordiazepoxide on punished and extinguished water consumption in rats

It has been postulated that behavioral inhibition due to punishment or extinction may be mediated by brain acetylcholine, and drugs which have disinhibitory action are thought to interact with this system. This notion was tested by comparing the effects of scopolamine, physostigmine and chlordiazepoxide on punished and extinguished water consumption. Scopolamine hydrobromide (0.3, 0.5 mg/kg, i.p.), a centrally and peripherally acting antimuscarinic agent and physostigmine sulfate, (0.3 mg/kg, i.p.), a centrally and peripherally acting acetylcholinesterase inhibitor, lowered both non-punished and punishment suppressed water intake and lick rate, whereas their quaternary analogs which primarily act in the periphery, had no significant effect at comparable dose levels. Scopolamine and physostigmine suppressed punished water consumption at lower dose levels than nonpunished intake. In contrast, chlordiazepoxide (5.0, 10.0, 20.0 mg/kg, i.p.) enhanced punished as well as non-punished water intake. In a further experiment comparing punishment and extinction suppression, scopolamine and physostigmine did not affect punished or extinguished water intake; chlordiazepoxide (5.0, 10.0, 20.0 mg/kg) reliably increased punished, but not extinguished licking on the water nozzle. These results suggest (1) that scopolamine and chlordiazepoxide do not act via a common mechanism, and (2) that punishment and extinction suppression are not a pharmacological entity.     

Development of tolerance to amnesic effects of chlordiazepoxide in relation to GABAergic and cholinergic neuronal systems

Chronic administration of benzodiazepines has been reported to produce tolerance in animals and humans. We investigated whether benzodiazepines produce tolerance to the amnesic effects and effects on benzodiazepine receptors, GABAergic and/or cholinergic neuronal systems of repeated administration of chlordiazepoxide, using a passive avoidance task and autoradiographic techniques. Tolerance developed to the amnesic effect of chlordiazepoxide when the drug was administered at a dose of 30 mg/kg (i.p.) once a day for 14 days. Bicuculline (1.0 and 1.5 mg/kg), a GABA_A receptor antagonist, did not induce amnesia in normal mice, but did so in chlordiazepoxide-tolerant mice. Muscimol (0.25 mg/kg), a GABA_A receptor agonist, in combination with a low dose of chlordiazepoxide, induced amnesia in normal mice, but not in chlordiazepoxide-tolerant mice. Scopolamine, an acetylcholine receptor antagonist, induced amnesia in normal mice, but not in chlordiazepoxide-tolerant mice. In the autoradiographical study, although repeated treatment with chlordiazepoxide had no effect on [³H]flunitrazepam and [³H]Ro 15-4513 binding to benzodiazepine receptors, it decreased [³H]muscimol binding to GABA_A receptors, with a decrease in affinity in the cortex and hippocampus. Furthermore, repeated administration of chlordiazepoxide increased [³H]quinuclidinyl benzilate binding to muscarinic acetylcholine receptors in the hippocampus. These results suggest that tolerance develops to the amnesic effects of chlordiazepoxide, and that tolerance may be due to down-regulation of GABA_A receptors and/or up-regulation of acetylcholine receptors.