Conditioned Defensive Burying Paradigm Research Articles

Chronic stress alters behavior in the conditioned defensive burying test: role of the posterior paraventricular thalamus

In the present studies, we examined the effects of chronic restraint on behavior in the conditioned defensive burying paradigm, a well-validated test of anxiety. This test is based on the findings that rodents tend to cover or bury the source of a noxious or aversive stimulus. However, little is known about whether prior chronic stress exposure can alter this anxiety-related behavior. In the present study, we examined whether chronic restraint affects indices of behavior in the conditioned defensive burying paradigm. Furthermore, since the posterior division of the paraventricular thalamus (pPVTh) regulates neuroendocrine activity specifically in chronically stressed but not control rats, we hypothesized that the pPVTh may also regulate any chronic stress-induced changes in behavior observed in the defensive burying test. Chronically stressed rats (30-min restraint per day for seven consecutive days) exhibited decreased latency to bury compared to control rats regardless of the presence of lesions suggesting increased reactivity to the shock in these animals. Importantly, pPVTh-lesioned chronically stressed rats exhibited increased duration and height of burying compared to control rats with pPVTh lesions, whereas no differences existed between sham-lesioned control and chronically stressed rats. Since both burying height and duration of burying are considered indices of anxiety in the defensive burying test, the present results suggest that the intact pPVTh may be important in dampening behaviors related to anxiety in chronically stressed rats.

Characterization of alpha-casozepine, a tryptic peptide from bovine alpha(s1)-casein with benzodiazepine-like activity.

Caseins are a known source of biologically active peptides. In this study, we have shown evidence of a novel anxiolytic activity in a tryptic hydrolysate of bovine α s1-casein. Injection of 3 mg/kg of this hydrolysate significantly reduced the epileptic symptoms caused by pentylenetetrazole in rats. Anxiety reduction was also observed when the hydrolysate was tested in the elevated plus-maze and in the conditioned defensive burying rat models. Peptides isolated from the hydrolysate were examined for their affinity for the γ-amino-butyric acid (GABA) type A receptor. Only one peptide, named α -casozepine, corresponding to the 91–100 fragment from bovine α s1-casein, expressed affinity for GABA A receptor. In vitro, the peptide had 10,000 less affinity for the benzodiazepine site of the GABA A than did diazepam. However, in the conditioned defensive burying paradigm it was 10-fold more efficient than diazepam. The difference observed between the in vitro and in vivo activity of α -casozepine could not been explained by an action via the peripheral-type benzodiazepine receptor; α -casozepine had no affinity for this receptor. The α -casozepine amino acid sequence could be related to the carboxyterminal sequence of the polypeptide diazepam binding inhibitor, an endogenous ligand of the central GABAA and peripheral-type benzodiazepine receptors.

Corticotropin-Releasing Hormone Microinfusion in the Central Amygdala Enhances Active Behaviour Responses in the Conditioned Defensive Burying Paradigm

The central nucleus of the amygdala (CeA) is known to be involved in the regulation of autonomic, neuroendocrine, and behavioural responses in stress situations. The CeA contains large numbers of corticotropin-releasing hormone (CRH) cell bodies, terminals and functional recognition sites. In the present study, the effects of locally infused CRH (30 ng) into the CeA, of freely moving Wistar rats in the conditioned defensive burying paradigm were examined. CRH administered into the CeA increases active (defensive burying and gnawing) behaviour towards a previously electrified probe, which was blocked by pretreatment of α-hCRH, the CRH receptor antagonist. This study clearly shows that the CeA CRH system is involved in the modulation of the CRH-induced behavioural stress response. These findings are discussed in terms of an enhancement of an anxiety response or a shift in coping style balance.

Nitrous oxide induces an anxiolytic-like effect in the conditioned defensive burying paradigm, which can be reversed with a benzodiazepine receptor blocker.

To investigate the anxiolytic effects of nitrous oxide (N2O), male hooded rats were tested in the conditioned defensive burying (CDB) test, a paradigm that exploits a propensity of rats to bury objects associated with aversive stimulation. A single, brief electrical shock was delivered to rats upon contact with an electrified prod, before exposure to one of four mixtures of N2O and oxygen (O2) (10-40% N2O) or room air (RA). Compared to RA-exposed animals, rats exposed to N2O exhibited a concentration-related reduction in duration and height of prod-directed "defensive" burying with floor bedding material; these measures reached statistical significance at 30% N2O. Pretreatment with 20 mg/kg of the benzodiazepine receptor blocker flumazenil, which alone had no effect, effectively antagonized a 30% N2O-induced decrease in burying. Horizontal locomotion and rearing were not significantly affected at concentrations of N2O that attenuated prod-directed burying. Treatment with the benzodiazepine anxiolytic standard, chlordiazepoxide (2.5-10.0 mg/kg) also resulted in dose-related attenuation of burying behavior. These findings show that N2O can induce effects similar to those of known anxiolytics in this paradigm and suggest a benzodiazepine mechanism in its mediation.

Beta-adrenergic antagonists attenuate withdrawal anxiety in cocaine- and morphine-dependent rats.

Rats were treated chronically with either cocaine (20 mg/kg/day, 14 days), morphine (incrementing doses of 10 mg/kg/day to 80 mg/kg, 11 days) or saline. During morphine or cocaine abstinence (48 h), dependent rats showed increased anxiety-like behavior in a conditioned defensive burying paradigm as evidenced by significantly shorter latencies to begin burying as well as a 4-fold increase in burying duration relative to saline-treated animals. This withdrawal-induced increase in burying behavior was blocked by pretreatment with either the beta-adrenergic antagonist propranolol (5 mg/kg) or the lipophobic selective beta 1-antagonist, atenolol (5 mg/kg). These results are consistent with the possibility that activation of peripheral beta 1 receptors may substantially contribute to withdrawal-induced anxiety and that beta-adrenergic antagonists could be useful in treating in cocaine and morphine dependent addicts.

Conditioned neuroendocrine and cardiovascular stress responsiveness accompanying behavioral passivity and activity in aged and in young rats

Mean arterial pressure (MAP), heart rate (HR), plasma epinephrine (E), plasma norepinephrine (NE), and plasma corticosterone (CORT) were measured in 3-month- and 24-month-old male Wistar rats exposed to a conditioned emotional stress response (CER) paradigm and a conditioned defensive burying (CDB) paradigm. In the CER situation blood samples were taken during reexposure to the training environment one day after a single inescapable footshock (0.6 mA, AC for 3 s) had been administered. In the CER paradigm the young rats displayed passive behavior (immobility) accompanied by an increase in plasma levels of CORT and E, whereas both the control and conditioned animals showed increased NE responses. Previously shocked aged rats exhibited an attenuated plasma NE response, whereas levels of E remained elevated to a greater extent. Aged animals showed elevated basal levels of CORT one day after footshock administration. Stress-induced immobility was preserved in the aged rats. These animals had an increase in basal MAP values and a decrease in basal HR values compared to young ones. In the CDB paradigm, rats were exposed to a nonelectrified probe 1 day after the repeated shock (2 mA/contact) procedure. Young rats displayed defensive burying accompanied by increments in MAP, HR, CORT, and NE. The aged animals showed similar hormonal, autonomic, and behavioral stress responses. Thus, the age-related alterations in neuroendocrine and autonomic response patterns are apparent in stressed animals during behavioral passivity in absence of control (CER) rather than during active control (defensive burying).

The effect of ipsapirone on behavioral and cardiac responses in the shock-probe/defensive burying test in male rats

The effects of the 5-HT 1A receptor agonist, ipsapirone, on cardiac and behavioural responses of male Wistar rats in a conditioned defensive burying paradigm for anxiolytics were investigated. The shocked rats displayed defensive burying accompanied by an increase in heart rate. Ipsapirone-treated rats (5 and 10 mg/kg i.p.) showed less burying behaviour than did vehicle-treated controls, and the tachycardiac response was also reduced in a dose-dependent way whereas eating behaviour was facilitated. The results demonstrate the effectiveness of ipsapirone, thereby suggesting the involvement of 5-HT 1A receptors in a conditioned anxiety situation that elicits an active coping behaviour and sympathetic activation.

Behavioral analysis of the effects of benzodiazepine receptor ligands in the conditioned burying paradigm

In the conditioned burying paradigm, 10 mutually exclusive behavioral sequences were encoded in order to characterize the effects of various benzodiazepine receptor ligands. It was found that each ligand produced a specific behavioral pattern, the elements of which were consistent with results obtained in other experimental situations. Whereas anxiolytic (diazepam, Ro 16-6028) and ‘anxiogenic’ ligands (FG 7142) both decreased the mean duration of burying, these two classes of drugs largely differed when approaches to the prod and escape movements away from the prod were considered. The benzodiazepine receptor antagonist Ro 15-1788 was devoid of effects on all of the behavioral sequences considered. The main characteristics of these behavioral profiles persisted during an extinction test, although the animals were no longer treated. It is proposed that additional behavioral measures, or better, an ethological analysis of the behavior may increase the potency of the conditioned defensive burying paradigm.

Behavioural Pharmacology of 5-HT

Contents: Section I: A.R. Cools, Introduction. A.R. Green, Behavioural Pharmacology of 5-HT: An Introduction. T.P. Blackburn, D.A. Martin, P. Slater, Is Rotational Behaviour in the Rat a 5-HT1A or 5-HT1B Mediated Response? A.J. Stoessl, C.T. Dourish, S.D. Iversen, Serotonic Mediated Behaviour Following Central or Peripheral Administration of the Selective NK-3 Tachykinin Agonist Senktide. Section II: P. Bevan, 5-HT and Sexual Behavior. S. Ahlenius, K. Larsson, New Aspects on the Serotonergic Modulation of Male Rat Sexual Behaviour. S.D. Mendelson, B.B. Gorzalka, Differential Roles of 5-HT Receptor Subtypes in Female Sexual Behaviour. M.D. James, S.M. Lane, D.R. Hole, C.A. Wilson, Hypothalamic Sites of Action of the Dual Effect of 5-HT on Female Sexual Behaviour in the Rat. L. R nyi, T. Lewander, 5-HT1A and 5-HT1B Agonists Produce Opposite Effects on the Ejaculatory Response Induced by Amphetamine in Rats. H.H.G. Berendsen, R.J.M. Smets, C.L.E. Broekkamp, Functional Interplay of Serotonin(5-HT)-Receptor Subtypes. Section III: P. Bevan, 5-HT and Aggression. B. Olivier, J. Mos, M. Tulp, J. Schipper, P. Bevan, Modulatory Action of Serotonin in Aggressive Behaviour. K.A. Miczek, P. Donat, Brain 5-HT System and Inhibition of Aggressive Behaviour. D.C. Blanchard, K. Hori, R.J. Rodgers, C.A. Hendrie, R.J. Blanchard, Differential Effects of Benzodiazepines and 5-HT1A Agonists on Defensive Patterns in Wild Rattus. C. Gentsch, M. Lichtsteiner, H. Feer, Competition for Sucrose-Pellets in Triads of Male, Wistar Rats, the Effects of Eight 5-HT- Agonists. Section IV: A.R. Cools, Depression and Psychosis. P. Willner, Towards a Theory of Serotonergic Dysfunction in Depression. J.F.W. Deakin, 5-HT Receptor Subtypes in Depression. J.A.M. van der Heyden, Modulation of the 5-HT System and Antipsychotic Activity. G.A. Kennet, G. Curzon, Mechanism of Action of 8-OH-DPAT on a Rat Model for Human Depression. P. Martin, A.M. Laporte, P. Soubrie, E. El Mestikawy, M. Hamon, Reversal of Helpless Behaviour in Rats by Serotonin Uptake Inhibitors. T.F. Meert, C.J.E. Niemegeers, Y.G. Gelders, P.A.J. Janssen, Ritanserin (R 55 667), an Original Thymosthenic. N.M. Barnes, B. Costall, A.M. Domeney, M.E. Kelly, R.J. Naylor, M.B. Tyers, The Abilities of 5-HT3 Antagonists to Inhibit the Hyperreactivity Caused by Dopamine Infusion into the Nucleus Accumbens of the Rat. M.A. Geyer, 5-HT2 Antagonists Increase Tactile Startle Habituation in an Animal Model of a Habituation Deficit in Schizophrenia. Section V: A.R. Cools, Feeding Behaviour. E. Goodall, T. Silverstone, Pharmacological Evidence for the Involvement of Serotonergic Mechanisms in Human Feeding. R. Samanin, Serotonin and Feeding. P.H. Hutson, G.A. Kennett, T.P. Donohoe, C.T. Dourish, G. Curzon, Opposite Effects of 5-HT1A and 5-HT1B/1C agonists on Food Intake. J.D. Leander, Effects of Selective Serotonergic Agonists on Palatability-Induced Ingestion. A.M.J. Montgomery, P. Willner, R. Muscat, 8-OH-DPAT Reliably Increases Ingestion of Solid but not Liquid Diets. C.L. Lawton, J.E. Blundell, Pharmacological Manipulation of 5-HT: Effect on Intake of Diets Supplemented with Either Sweet or Bland Carbohydrates. Section VI: T. Archer, 5-HT, Pain and Anxiety. O-G. Berge, C. Post, T. Archer, The Behavioural Pharmacology of Serotonin in Pain Processes. C.L. Broekkamp, F. Jenck, The Relationship Between Various Animal Models of Anxiety, Fear-Related Psychiatric Symptoms and Response to Serotonergic Drugs. P. Soubrie, 5-HT1A Receptors: A Bridge Between Anxiety and Depression? M.B. Tyers, A Review of the Evidence Supporting the Anxiolytic Potential of 5-HT3 Receptor Antagonists. J. Mos, B. Olivier, Ultrasonic Vocalizations by Rat Pups as an Animal Model for Anxiolytic Activity: Effects of Serotonergic Drugs. S.A. Lorens, H. Mitsushio, L.D. Van der Kar, Effects of the 5-HT1A Agonist Ipsapirone on the Behavioural, Endocrine and Neurochemical Responses to Conditioned Fear. P. Moser, Buspirone, Ipsapirone and 5-HT1A-Receptor Agonists Show an Anxiogenic-Like Profile in the Elevated Plus-Maze. A. Fernandez-Guasti, E. Hong, Antianxiety Effect of Various Putative 5-HT1 Receptor Agonists on the Conditioned Defensive Burying Paradigm. B.Costall, A.M. Domeney, P.A. Gerrard, B.J. Jones, M.E. Kelly, N.R. Oakley, M.B. Tyers, The Anxiolytic Activities of the 5-HT3 Receptor Antagonists GR38032F, ICS 205-930 and BRL 43694. J. Mos, J.A.M. van der Heyden, B. Olivier, Behavioural Effects of 5-HT3 Antagonists in Animal Models for Aggression, Anxiety and Psychosis. Section VII: T.U.C. Jarbe, T.Archer, 5-HT: Drug Discrimination and Aversion. W. Koek, F.C. Colpaert, Receptor Mechanisms of the Discriminative Stimulus Properties of Putative Serotonin Agonists. F.G. Graeff, Serotonin and Aversion. R.A. Glennon, R. Young, M.E. Pierson, Stimulus Properties of Arylpiperazine Second Generation Anxiolytics. J.E. Barrett, S.N. Olmstead, Z. Lei, C. Harrod, S.M. Hoffmann, K. Glover, M.A. Nader, B.A. Weissman, Behavioural, Neurochemical and Discriminative Stimulus Effects of Spiroxatrine, a Putative 5-HT1A Receptor Antagonist. I. Lucki, J.A. South, Rapid Training of the Stimulus Properties of Selective 5-Hydroxtryptamine1A Agonists. Section VIII: P. Bevan, S. Lorens, T. Archer, Behavioural Pharmacology of 5-HT: Possible Progress in the Laterality of Concepts.

The contrasting effects of diazepam and yohimbine on conditioned defensive burying in rats

The conditioned defensive burying (CDB) paradigm consists of placing rats in a test chamber with wood shavings on the floor, shocking them with a shock prod, and recording the time each rat spends in a burying response to the prod during a 15-min test session. This experiment revealed contrasting effects of the anxiolytic agent, diazepam (0.5 and 2 mg/kg, i.p.), and the anxiogenic agent, yohimbine (0.5 and 2 mg/kg, i.p.), on CDB of male hooded rats. During the test session, diazepam-injected rats spent significantly less time engaged in CDB than did vehicle-injected rats. On the other hand, yohimbine-injected rats spent significantly more time burying than did the vehicle-injected rats, and did so in a dose-dependent fashion. Twenty-four hours later when a retention session was conducted without any additional shocks and injections, both the facilitative effects of yohimbine and the suppressive effects of diazepam on the CDB were still observed in terms of duration, number, and latency of burying, as well as in the height of piles accumulated. These results indicate that the postshock CDB could be differentiately affected by anxiolytic and anxiogenic agents. The CDB paradigm might represent an appropriate model for studying the pharmacological analysis and neuronal mechanisms of anxiety and/or fear in animals.

Behavioral field analysis in two strains of rats in a conditioned defensive burying paradigm

Two strains of rats (albino Wistar and hooded PVG/c) were exposed to a conditioned defensive burying paradigm that consisted of placing rats in a test chamber with bedding material on the floor, shocking them with a shock prod, and recording the time each rat spent in burying responses toward the prod. Various behaviors other than burying (freezing, grooming/paw licking) were observed by a time-sampling procedure during the control, conditioning, and extinction sessions, each of which was 15 min in duration. Wistar rats generally showed behavioral inhibition, as evidenced by less burying, lower exploratory and ambulatory behavior, and higher freezing behavior. PVG/c rats spent significantly more time engaged in burying and accumulated more bedding material in the conditioning session than did the Wistar rats. No significant differences between the two strains of rats were observed during the extinction session in terms of these measurements. The results indicate that Wistar rats have a greater tendency to freeze when coping with the noxious stimulus in a conditioned defensive burying paradigm, whereas the dominant coping style for PVG/c rats is defensive burying.

The inhibitory effect of diazepam on conditioned defensive burying is reversed by picrotoxin

The ability of picrotoxin to reverse the effect of diazepam was studied using the conditioned defensive burying paradigm. Although picrotoxin alone had no detectable effect of the conditioned defensive burying response of rats, picrotoxin was able to reverse the usual inhibitory effect of diazepam on defensive burying. These results suggest that the anxiolytic effect of diazepam may depend upon the integrity of GABAergic neural systems.

Effect of septal lesions on conditioned defensive burying

Every control rat shocked by a wire-wrapped prod mounted on the wall of a test chamber buried the prod with bedding material from the floor of the chamber. Although this conditioned defensive burying was also observed in every rat with a lesion of the anterior septum (Experiment 2), no rat with a lesion of the entire septum (Experiment 1) or a lesion limited to the posterior septum (Experiment 2) was observed to engage in this behavior. These results confirm previous reports of the involvement of the septal area in defensive behavior and provide the first demonstration of the utility of the conditioned defensive burying paradigm in assessing the behavioral effects of limbic lesions.

Conditioned defensive burying: A new paradigm for the study of anxiolytic agents

Behavioral paradigms that have been designed to mimic forms of learning that are important for the survival of animals in the wind, rather than to minimize the contributions of adaptive predispositions, may prove to be particularly useful for studying the behavioral effects of drugs. In the present experiments, the propensity of rats to bury sources of aversive stimulation was disrupted in a dose-dependent fashion by a single injection of the anxiolytic drug, diazepam. This suggested that the conditioned defensive burying paradigm could prove to be a valuable addition to the paradigms available for studying anxiolytic effects. Supporting this view were two additional observations. First, the relative potencies of diazepam, chlordiazepoxide, and pentobarbital in the burying paradigm compared favorably with their relative potencies in clinical settings. Second, the effects of anxiolytics on conditioned burying appeared to be dissociable from the effects of other drugs that disrupt this behavior.