Shuttlebox Avoidance Research Articles

Evaluation of perinatal flumazenil effects on the behavior of female RLA/Verh rats in anxiety tests and shuttle box avoidance

The present study investigated the effects of perinatal flumazenil (Ro 15-1788, a benzodiazepine receptor antagonist), given from gestational day 15 to the 14th day after giving birth, at two doses (3.5 and 6.3 mg/kg/ day) on the behavior of female RLA/Verh rats. This rat line has been selectively bred for non-acquisition of two-way active avoidance. Offspring of treated/non-treated dams were tested when adults for two-way active (shuttle box) avoidance acquisition. For comparison reasons additional offspring coming from the same treatments were used in an hyponeophagia test and in both an open field and a plus maze tests. The results show that perinatal flumazenil, specially the lower dose (and also the highest dose, although only in the final phases of the shuttle box training) was able to improve two-way active avoidance acquisition, as it has been previously found with males, whereas it failed to show any effect in the hyponeophagia task, the open field and the plus-maze tests. As two-way active avoidance acquisition can be enhanced both by reducing emotionality/anxiety or by improving memory, it is suggested that flumazenil treatment could have affected either one or both processes.

Muscarinic acetylcholine receptor immunoreactivity in the amygdala—II. Fear-induced plasticity

Changes in the distribution of muscarinic acetylcholine receptor-immunoreactive neurons were examined in the amygdaloid complex at different time-intervals following a single training session of active shock avoidance in a two-way shuttle-box. Muscarinic acetylcholine receptors were visualized using M35, a monoclonal antibody raised against purified muscarinic acetylcholine receptor protein. Both in naive animals and 2 h after active shock avoidance training, muscarinic acetylcholine receptor immunoreactivity was high in the central nucleus, and only low to moderate in other amygdaloid regions. Twenty-four hours after training, however, the muscarinic acetylcholine receptor immunoreactivity distribution pattern was reversed, showing a dramatic increase in the corticomedial nucleus, while in contrast, in other amygdaloid regions including the central nucleus, muscarinic acetylcholine receptor immunoreactivity was reduced to only a few scattered neurons. Additional studies with a modified experimental design indicated that fear conditioning mechanisms in association with the severity of the aversive stimuli, and not the learning of the avoidance response, may account for the changes in muscarinic acetylcholine receptor immunoreactivity in the amygdala. These results are consistent with the prominent role of the central nucleus in the conditioning and expression of the fear response. A closer examination revealed that 8 h after training the changes in both the central and corticomedial nuclei became significant. The differences still existed after 25 days, but three months after the training session the receptor distribution was returned to normal. The long-lasting, but reversible nature of these changes indicates that fear conditioning is accompanied by a dynamic plasticity of muscarinic acetylcholine receptor immunoreactivity in the amygdaloid complex.

Effects of low doses of physostigmine on avoidance learning and EEG in two strains of mice

The effects of the cholinomimetic drug, physostigmine (0, 0.01, 0.025, 0.05 and 0.1 mg/kg, i.p.), on shuttle-box avoidance learning and electroencephalographic (EEG)activity were investigated, in two separate studies, in mice belonging to the inbred C57BL/6 (C57) and DBA/2 (DBA) strains. The results of the behavioral investigation showed a consistent, significant enhancement of avoidance performance, on the whole of 5 daily training sessions, in C57 mice treated with the lowest dose (0.01 mg/kg) and in DBA mice treated with the highest doses (0.05 and 0.1 mg/kg) of the drug. Doses higher than 0.01 mg/kg, in C57 mice, and lower than 0.05 mg/kg, in DBA mice, had no significant effect. The avoidance improvements induced by physostigmine cannot be ascribed to a general behavioral activation, since the doses that increased avoidance responses did not affect or even depressed spontaneous locomotor activity. The same doses of treatment which increased avoidance responding, also induced, in the same strains, consistent enhancement of 4–7 Hz (theta) EEG band power and decrease of 7–12 Hz (alpha) band power. Results suggest that the effects induced by physostigmine on the EEG and on the shuttle-box performance of mice are related to the same neurochemical systems, and are dependent upon the interaction of the dose with specific strain sensitivity.

2334 A ¦ 14C¦ 2-deoxy-D-glucose study of the hippocampal subfields related to shuttlebox avoidance learning in the rat. The third report

2334 A ¦ 14C¦ 2-deoxy-D-glucose study of the hippocampal subfields related to shuttlebox avoidance learning in the rat. The third report

A long-lasting increase and decrease in synaptic excitability in the rat lateral septum are associated with high and low shuttle box performance, respectively

In a series of experiments with rats, using evoked field potentials, the influence of massed trial training in 2-way shuttle box avoidance and step-through passive avoidance tasks was studied on the synaptic excitability of the lateral septum (LS) neurons and on the induction of long-term potentiation in the lateral septum in vivo. The majority of rats that attained a high performance level in the shuttle box task exhibited, after the shuttle box training, a long-lasting enhancement of synaptic excitability of lateral septum neurons, whereas most of the rats with low performance in the shuttle box showed a long-lasting depression in the LS synaptic excitability. Both types of excitability changes disappeared within 24 h. Neither the first habituation session in the passive avoidance apparatus nor the subsequent one-trial learning in passive avoidance task has a marked influence on lateral septum synaptic excitability. Both high-performance and low-performance rats exhibited a long-term potentiation (LTP)-like potentiation of synaptic excitability of the lateral septum neurons after frequency stimulation of the fimbria fibers although the amount of LTP in high performance rats was slightly higher than that in low performance animals.

Behavioral Characteristics of Rats Selectively Bred for High and Low Avoidance Shuttlebox Response

Abstract Selective breeding of rat strains showing high and low avoidance behavior in the shuttlebox test has been performed since 1985. To elucidate the postnatal behavior of the high and low avoidance strains, animals from both lines were subjected to an open‐field test, wheel cage activity test and Biel maze test in the 13th, 14th and 16th generations, respectively. No significant differences in any parameter in the open‐field test were observed between high and low avoidance lines. However, animals from the high avoidance line showed higher motor activity in the wheel cage and fewer errors in the Biel maze than the low avoidance line.

Behavioral consequences of neonatal injury of the neocortex

Several strains of autoimmune mice spontaneously develop molecular layer ectopias that are similar in appearance to those seen in humans and are caused by disturbances in neocortical neuronal migration. These mice also exhibit behavioral anomalies, some of which correlate with ectopias, others with the immunological disorder. In this study, we induced neocortical ectopias (via puncture wounds) and microgyria (via freezing lesions) in the neocortex of 1-day-old (newborn) mice without immune disorders in an attempt to further disentangle the effects of autoimmunity and of cortical malformation on behavior. In addition, we wished to compare the behavioral effects of small ectopias to larger microgyric lesions. DBA mice were assigned at birth to receive either a puncture wound or freezing lesion of either the left or right hemisphere. An independent group was subjected to sham surgery. In adulthood, these mice were given a battery of tests designed to measure lateralization and learning capacity. Lesioned mice (irrespective of hemisphere or type of damage) performed poorly when compared to sham-operated animals in discrimination learning, in a spatial Morris Maze Match-to-Sample task, and in a Lashley Type III maze. In shuttlebox avoidance conditioning, where immunological disorder has been shown to compromise behavioral performance in autoimmune mice, there was no difference between lesioned and sham animals. These results (1) support the dissociation between the effects of developmental neocortical anomalies and autoimmune disease on behavior (2) reveal similarities between spontaneous and induced neocortical malformations and (3) fail to support a difference in behavioral effects between ectopias and microgyria.

Specific deficit of the ON response in visual transmission by targeted disruption of the mGIuR6 gene

Taking advantage of the restricted expression of metabotropic glutamate receptor subtype 6 (mGIuR6) in retinal ON bipolar cells, we generated knockout mice lacking mGIuR6 expression. The homozygous mutant mice showed a loss of ON responses but unchanged OFF responses to light. The mutant mice displayed no obvious changes in retinal cell organization nor in the projection of optic fibers to the brain. Furthermore, the mGIuR6-deficient mice showed visual behavioral responses to light stimulation as examined by shuttle box avoidance behavior experiments using light exposure as a conditioned stimulus. The results demonstrate that mGIuR6 is essential in synaptic transmission to the ON bipolar cell and that the OFF response provides an important means for transmitting visual information.

Corticotropin-releasing hormone (CRH) antisense oligodeoxynucleotide induces anxiolytic effects in rat.

Antisense oligodeoxynucleotide complementary to the start coding region of rat corticotropin releasing hormone (CRH) mRNA was intracerebroventricularly infused into rats three times at 12-h intervals. In the shuttle-box avoidance procedure antisense-treated rats showed, within 6 h, significant acceleration and increase in the total number of discriminative avoidance responses compared with controls, treated with the corresponding sense probe or vehicle alone. Following the shuttle-box experiment hypothalamic CRH hybridization signals and immunoreactivity were reduced, while CRH immunoreactivity in the median eminence remained unchanged. Plasma ACTH and corticosterone were decreased in antisense-treated animals. It is likely that in addition to a selective blockade of CRH translation, antisense treatment may also interrupt secretion of CRH. Antisense targeting of the hypothalamo-hypophysial-adrenal axis may provide new strategies for the neuropharmacology of affective disorders.

Scopolamine induces recovery of shuttle box avoidance behavior after frontal cortex ablation

The learning and reversal of shuttle box active avoidance behavior in animals with a bilateral frontal cortex ablation was investigated during and after scopolamine or pilocarpine treatment. Scopolamine facilitated the performance of the avoidance task in normal animals and in those with frontal cortex lesions and also increased the number of intertrial responses, while pilocarpine increased the deleterious effects of the lesions. Furthermore, in the absence of scopolamine, the animals previously treated with the drug showed that its beneficial effects persisted while the number of intertrial responses were no longer increased. The results indicate that the beneficial effects of scopolamine treatment on active avoidance behavior are independent from the effects observed on intertrial activity since only the former are observed after drug withdrawal. Therefore, scopolamine treatment seems to induce a long lasting recovery process in frontal cortex ablated animals.

Learned helplessness sensitizes hippocampal norepinephrine to mild restress

A proportion of rats exposed to inescapable tailshock stress displayed a performance deficit, termed learned helplessness, in a subsequent shuttlebox avoidance task. The technique of in vivo microdialysis was used to determine hippocampal norepinephrine levels in learned helpless, nonhelpless and nonprestressed control rats. Similar basal norepinephrine levels were detected in samples between rat groups. Following an exposure to a milder form of inescapable shock, an increase in norepinephrine output was detected in learned helpless rats, which was significantly greater than nonhelpless, nonprestressed, or control animals. Thus, inescapable stress appears to sensitize the hippocampus to increase norepinephrine release in response to a subsequent smaller stressor. This hypersensitivity might underlie the avoidance impairment of learned helplessness. Therefore, the possibility exists that similar neurochemical changes may also be responsible for some of the symptoms of human posttraumatic stress disorder (PTSD), such as the poor coping associated with seemingly mild stress.

The effects of control on stress-induced gastric erosions: The use of active shuttle-box avoidance learning with yoked controls

The aim of the present study was to investigate effects of instrumental control on the development of stress-induced gastric erosions by using a shuttle-box paradigm with yoked controls. In Experiment 1 the learning conditions had a reinforcement ratio of only 70% to increase stress during the short-term learning session. No significant differences of the mean cumulative length of gastric erosions between active avoiding and yoked groups were found. Experiment 2 tested three different reinforcement conditions (70%, 90%, 100%) with yoked groups. Again, no significant differences of the mean cumulative length of erosions between active avoiding and yoked control groups were obtained. Instead, the length of erosions decreased with increasing reinforcement. Taken together, the data show that the frequency of unavoided noxious stimuli as a function of the reinforcement schedule can be seen as a major influence on the development of gastric erosions in a shuttle-box paradigm.

Differential interactions between ethanol and Ro 15-4513 on two anxiety tests in rats

The effects of low (2 g/kg) and high (4 g/kg) doses of ethanol and their interaction with the imidazobenzodiazepine Ro 15-4513 (a partial inverse agonist of the benzodiazepine receptor) were studied in two different models of anxiety in rats: the “elevated plus-maze” test and the early acquisition of two-way (shuttlebox) avoidance. In the elevated plus-maze, ethanol (2 g/kg) increased the percentage of entries into the open arms (%EOA) and both ethanol doses increased the percentage of time spent into the open arms (%TOA), thus indicating an anxiolytic action which was reversed by Ro 15-4513 (5 mg/kg). By contrast, Ro 15-4513 did not counteract the anxiolytic effect of the low dose of ethanol in the acquisition of shuttlebox avoidance. Thus, the treatment with 2 g/kg of ethanol (plus either vehicle or Ro 115-4513) significantly. increased the total number of avoidances. Conversely, animals treated with 4 g/kg of ethanol showed impaired shuttlebox avoidance acquisition, and this effect was completely reversed by Ro 15-4513. Ro 15-4513 was without effect on its own in any of the anxiety-related parameters (i.e., %EOA, %TOA, and avoidance acquisition). The results indicate a different pattern of ethanol effects and Ethanol × Ro 15-4513 interactions depending upon the task used.

Anxiolytic profiles of alprazolam and ethanol in the elevated plus-maze test and the early acquisition of shuttlebox avoidance

Rats pretreated either with the anxiolytic triazolobenzodiazepine alprazolam (0.75 and 1.75 mg kg −1 i.p.) or ethanol (1, 2, 3 and 4 g kg −1 p.o.) were tested in both the elevated plus-maze and the early acquisition of shuttlebox avoidance. Both substances induced overall anxiolytic effects in the plus-maze, with the 0.75 mg kg −1 being the most effective alprazolam dose and 1–3 g kg −1 being the most effective ethanol doses. Both drugs were also anxiolytic in the shuttlebox, since 1.75 mg kg −1 alprazolam and 2–3 g kg −1 ethanol improved acquisition of the task. Correlational and factor analysis showed that behaviour in the open arms of the plus-maze and efficiency in shuttlebox avoidance acquisition are positively associated, thus providing further support to the contention that the early acquisition of shuttlebox avoidance is an animal model of anxiety.

Behavioral and immunological events induced by electrical stimulation of the rat midbrain periaqueductal gray region.

We report here on the immunological and behavioral alterations induced by stimulation of the mesencephalic periaqueductal gray matter (PAG), a component of the brain aversive system. Male Wistar rats were implanted with stimulating electrodes in the caudal dorsolateral part of the PAG. After recovery, animals were screened for aversive behavior, characterized by running, jumping, vocalization or freezing reaction. Then, rats were subdivided to those which could control aversive stimulation (AS) by switch-off response (cAS group) and those which could not interrupt AS (uAS group). After sensitization with bovine serum albumin (BSA) in complete Freund's adjuvant, rats were stimulated 3 times/week for 40 days, each session lasting 30 min/rat. Immunological assessment included antibody production and hypersensitivity skin reactions to BSA 14 and 21 days after immunization. A behavioral profile of aversively stimulated animals was determined by a poststartle response, open field (OF) activity and two-way shuttle-box avoidance task. The results revealed elevated antibody production to BSA in cAS and lowered in uAS rats, compared to sham-stimulated and intact controls. Arthus and delayed hypersensitivity skin reactions increased in PAG-stimulated animals on day 14 but not on day 21 after immunization. Poststartle response was enhanced both in cAS and uAS rats. Along with immunopotentiation, administration of cAS produced hyperactivity in OF test and facilitation of the active avoidance learning, whereas uAS caused only moderate suppression of rearing in a novel OF environment. Physiological implications and possible mechanisms that may account for PAG-mediated immunobehavioral changes are outlined.

A [ 14C] 2-deoxy-D-glucose study of the hippocampal subfields related to shuttle-box avoidance learning in the rat

A [ 14C] 2-deoxy-D-glucose study of the hippocampal subfields related to shuttle-box avoidance learning in the rat

Similar effects of ethanol and flumazenil on acquisition of a shuttle‐box avoidance response during withdrawal from chronic ethanol treatment

1. Acquisition of a two-way shuttle-box avoidance response is facilitated by ethanol. This facilitated acquisition of an avoidance response to ethanol was attenuated during withdrawal from chronic-ethanol diet intake (i.e. tolerance developed by ethanol). The deficit in the avoidance task after chronic ethanol treatment could be overcome by increasing the dose of ethanol. 2. Flumazenil, a benzodiazepine antagonist, also facilitated acquisition of the avoidance response in control rats. This response to flumazenil was significantly reduced during withdrawal from chronic-ethanol treatment. This reduced avoidance responding during withdrawal also could be overcome by increasing the dose of flumazenil. 3. The benzodiazepine-inverse agonist, RO 15-4513, produced a deficit in avoidance responding that was antagonized by both ethanol and flumazenil in a dose-related manner. 4. To determine whether flumazenil has the properties of a benzodiazepine agonist, it was established that, unlike the benzodiazepine chlordiazepoxide, flumazenil did not enhance the ethanol-induced deficit in the aerial righting reflex. Additionally, flumazenil blocked the action of chlordiazepoxide in this procedure, consistent with the benzodiazepine antagonist action of flumazenil. 5. Data collected are consistent with the hypothesis that an endogenous substance with the properties of a benzodiazepine-inverse agonist antagonizes the anticonflict actions of acutely administered ethanol during withdrawal from chronic-ethanol exposure.

Flumazenil Prevents the Anxiolytic Effects of Diazepam, Alprazolam and Adinazolam on the Early Acquisition of Two-Way Active Avoidance

The effects of diazepam (DZ, 4 mg/kg), alprazolam (ALP, 1.25 mg/kg) and adinazolam (ADIN, 6 mg/kg), as well as their interaction with the benzodiazepine receptor antagonist flumazenil (Ro15-1788), were studied on the early acquisition of two-way active (shuttlebox) avoidance in male Sprague-Dawley rats. The three benzodiazepines increased shuttlebox avoidance acquisition, and their effects were prevented (antagonized) by flumazenil (10 mg/kg). The present results indicate that central benzodiazepine (BZ) receptors are involved in the anxiolytic effects of diazepam and triazolobenzodiazepines on the early acquisition of two-way active avoidance.

A cerebral ischemia model produced by injection of microspheres via the external carotid artery in freely moving rats

We produced an improved microembolism model of cerebral focal ischemia by injection of 1000–2000 microspheres (50 ± 5 μm diameter) via a tube retrogradely inserted into the right external carotid artery in freely moving rats. The group injected with 2000 spheres showed a much more severe mortality rate as well as neurological signs than did the 1000-sphere group. Brain water content of the 2000-sphere group was examined and found to show an increase from 4 to 24 h after embolization in the right hemisphere, indicating serious brain edema. Severe neurological signs and individual deaths by embolization were most likely related to the extent of development of brain edema. Examination of learning behavior by shuttle-box avoidance revealed partial but significant impairment of learning in the 1000-sphere group. Autoradiographic studies for muscarinic acetylcholine receptors and protein kinase C binding sites were conducted. Both these binding sites decreased in number, but protein kinase C seems to be more susceptible to ischemic injury than muscarinic acetylcholine receptors. The observation was considered to be closely related with an impairment of learning. The present study suggests that our microembolism model in freely moving rats is useful for investigations of the early phase and late phase of cerebral ischemia.

Light-dark discrimination after sciatic nerve transplantation to the sectioned optic nerve in adult hamsters

In adult golden hamsters ( Mesocricetus auratus), the optic nerve was bilaterally sectioned with one side grafted with the sciatic nerve to make a bridge to the ipsilateral superior colliculus. Shuttle-box avoidance was tested using light as the conditioned stimulus. Three of the five transplanted animals revealed statistically significant increase in percentages of avoidance. A significant increase in the avoidance scores was also observed in 15 normal hamsters, but none of 13 blind hamsters showed such an increase. Intertrial responses, which represent spontaneous responses, did not show significant changes. We conclude that some of the transplanted animals can discriminate between light and dark, probably through their restored visual pathway.