Defensive Conditioned Reflex Research Articles

Action of Serotonin Precursor Synthesis 5-Oxytryptophan on EPSP Recorded in Premotor Interneurons of Snail after Formation of Conditioned Defensive Reflex

Action of Serotonin Precursor Synthesis 5-Oxytryptophan on EPSP Recorded in Premotor Interneurons of Snail after Formation of Conditioned Defensive Reflex

Changes in Membrane and Threshold Potentials of Command Neurons in Terrestrial Snail during Development of a Conditioned Situational Defensive Reflex.

Changes of the electrical characteristics of command neurons of defensive behavior caused by the development of a conditioned situational defensive reflex were studied experimentally under in vitro conditions on preparations of the nervous system of snails. After learning, the membrane and threshold potentials of command neurons LPa3 and RPa3 significantly decreased and excitability of the studied neurons increased.

Effects of Decreases in Dopamine (D1 and D2) Receptor Expression in the Basolateral Amygdala of Rats on Conditioned Defensive Reflexes

RNA interference studies using lentivirus transduction were performed to investigate the effects of decreased expression of dopamine receptors (D1R and D2R) in the basolateral nucleus of the amygdala on the acquisition and extinction of conditioned defensive reflexes in rats. Immunohistochemical staining showed that transduction affected both neurons (mean 19%) and astrocytes (73%). As compared with controls, rats with decreased D1R expression showed degraded acquisition and facilitated extinction of a conditioned defensive reflex to sound, with acceleration of extinction of a passive avoidance reflex, and slowing of learning to seek a hidden platform in the Morris water maze by 1–2 days. In conditioned reflex fear, the behavior of rats with prolonged freezing changed more than that of rats with short periods of freezing when D1R expression in the amygdala was decreased. In rats with decreased D2R expression, extinction of the classical defensive reflex and the passive avoidance reflex was quicker. These results provide evidence of differences in the roles of D1R and D2R in the amygdala – functioning of D1R, in contrast to D2R, is important for acquisition of defensive refl exes and the manifestation of conditioned refl ex fear in the form of prolonged freezing. The activity of both D2R and D1R is significant for the resistance of reflexes to extinction.

Influence of low-intensity variable magnetic field with proton magnetic resonance spectrum frequencies of dopamine to development of a conditioned defensive reflex of gastropods

Influence of low-intensity variable magnetic field with proton magnetic resonance spectrum frequencies of dopamine to development of a conditioned defensive reflex of gastropods

Behavior of Rats with High and Low Levels of Freezing in Defensive Situations and on Selection of Food Reinforcement

Behavior in rats with different levels of freezing in a classical defensive conditioned reflex was compared on acquisition of conditioned passive and active avoidance reflexes and on selection of food reinforcement of different values. Rats with prolonged freezing acquired the passive avoidance reflex better and retained it longer during extinction than animals with shorter freezing. At the same time, the active avoidance reflex in the shuttle box was acquired more easily by animals with short periods of freezing. Rats with prolonged freezing preferred a delayed and more valuable reinforcement in the model of choosing food reinforcements of different values (low level of impulsivity), while animals with short freezing preferred the low-value reinforcement without a delay (high level of impulsivity). The thresholds of pain sensitivity were no different in rats of the different groups. Thus, rats with prolonged freezing demonstrated a passive behavioral strategy in defensive situations and a low level of impulsivity, while rats with short freezing used an active behavioral strategy and showed a high level of impulsivity.

The Role of Intracellular Calcium in Changing of ElectricalCharacteristics of Premotor Interneurons in Intact Snails and Snails During Various Forms of Plasticity

It was previously shown that both associative learning and the formation of long-term sensitization led to the increase in excitability of premotor interneurons of the defensive behavior of terrestrial snail Helix lucorum. In the present study, we analyzed the role of intracellular calcium ions in the maintenance of increased excitability in premotor interneurons of terrestrial snail after the formation of a conditioned defensive reflex. It was shown that the increase of the intracellular Ca2+ concentration after adding caffeine to the solution washing the nervous system of the mollusk led to a decrease of the threshold of action potential and to an increase of the critical level of depolarization without a change of the membrane potential of premotor interneurons in both intact and trained snails. The decrease of the intracellular Ca2+ concentration in premotor interneurons by the intracellular injection of (ethylene glycol-bis (2-aminoethylether)-N, N, N, N-tetraacetic acid) (EGTA) resulted in a significant increase of the threshold of generation of the action potential in intact snails. But the values of threshold of generation of the action potential in trained snails after injection of EGTA did not significantly differ from the values of studied parameters before injection. After application of the membrane-penetrating chelator, BAPTA-AM, the changes in the membrane and threshold potentials of premotor interneurons of intact and trained snails were not observed. Our results demonstrated that both the increase and decrease of intracellular Ca2+ concentration were not involved in maintaining the changes of membrane characteristics of premotor interneurons observed after associative learning.

The Role of β1,2-Adrenoceptors in the Amygdala in the Behavior of Rats with Different Levels of Freezing in Conditioned Reflex Fear

Individual sensitivity to blockade of β1,2-adrenoceptors was studied by dividing rats into groups depending on the manifestation of conditioned reflex fear in a classical defensive conditioned reflex (low- and high-freezing animals) and on the level of anxiety in the elevated plus maze and dark-light box tests (highand low-anxiety animals). The effects due to local administration of the β1,2-adrenoceptor antagonist propranolol (1.25 μg/0.5 μl) and physiological saline (controls, 0.5 μl) into the basolateral amygdala were compared in the different groups of rats. Administration of propranolol into the amygdala before testing of previously acquired conditioned reflex fear led to a decrease in freezing time in response to the conditioned signal only in low-freezing animals, but not in high-freezing animals. Administration of propranolol into the amygdala accelerated extinction and degraded the productivity of retraining in high-freezing rats, having virtually no effect on low-freezing animals. In addition, administration of propranolol into the amygdala did not induce any significant changes in measures of anxiety in these tests in either high- or low-anxiety rats. A difference in the sensitivity of high- and low-freezing rats to injections of propranolol into the amygdala was seen. Amygdalar β1,2-adrenoceptors play a significant role in the acquisition and extinction of conditioned reflex fear in high-freezing rats, facilitating the appearance of prolonged freezing and resistance to extinction of the reflex.

The impact of the new derivative of nicotinic acid with anti-hypoxic activity on the functions of the central nervous system

The aim of the work was to study the effect of the complex compound of nicotine acid with antihypoxic activity under the code πQ-1043 on the function of the central nervous system. The experiments were performed on male mice of the SHR line. Influence of the compound on the function of the central nervous system was evaluated in the tests “open field”, conditioned-defense reflex of avoidance and corazole seizures. It was found that the compound πQ-1043 at a dose of 25 mg/kg increases emotional reactivity and reduces the coefficient of mobility of mice in the “open field” test, increases the latent time of the conditionally defensive reflex of avoidance, inhibits the development of seizures and increases the life expectancy of animals after administration of corazole. Such changes in the studied parameters indicate that the compound πQ-1043 has a depressing effect on the central nervous system function. It is assumed that the identified effect may be one of the components in the mechanism of antihypoxic action of the compound.

Carnosine modulates oxidative homeostasis and levels of neurotransmitters in the brain in models of learning with positive and negative reinforcement

We compared the effects of the dipeptide carnosine on learning and the biochemical parameters in the brain of rats trained for defensive and food-procuring conditioned reflexes. In the first series, the animals were trained for active avoidance behavior; in the second series, the rats were trained for the food-procuring conditioned reflex in a modified shuttle box. After training, the hypothalamus and cortex were dissected and used for evaluation of lipid peroxidation processes and the levels of monoamine neurotransmitters. The activating effect of carnosine was observed during the entire training period of defensive training, whereas during training for the food-procuring reflex it was observed only in the first two sessions. In both training series, impairments of oxidative homeostasis were found in the brain; these were efficiently corrected with carnosine. This effect of carnosine may explain its positive influence on learning. Moreover, in both models, carnosine increased the contents of the main monoamine neurotransmitters in the hypothalamus. These data led us to the conclusion about high prospectivity of further studies of the carnosine modulatory effects in the nervous system.

Studies of Histone H3 Methylation during the Formation of Long-Term Memory

Post-translational modification of histones plays in important role in chromatin remodeling and is involved in regulating gene expression during the formation of long-term memory. While histone acetylation and phosphorylation have been studied intensely for several years, studies of the role of methylation in learning have barely started. Histone methylation is interesting because it can both activate and inhibit gene expression. In a model of learning a conditioned defensive food aversion reflex in the mollusk Helix, we analyzed histone H3 trimethylation at lysine 4 (H3K4) and histone H3 dimethylation at lysine 9 (H3K9), which are associated with gene induction and repression respectively. These experiments showed that on consolidation of long-term memory, the Helix CNS shows a significant increase in histone H3 methylation at both lysine 4 and lysine 9. These data provide evidence for the involvement of histone methylation in the epigenetic mechanisms of formation of long-term memory in the mollusk Helix both at the levels of both activation and repression of transcription. In addition, induction of histone H3 methylation at lysine 9 was found to reflect the influences of inhibitory processes, which play an important role in CNS functioning.

Effects of Short-Term Administration of Haloperidol on the Background of Impairments to Brain Metabolism and Neuron Activity

The effects of amphetamine and haloperidol on spike activity levels, the ability to acquire a conditioned defensive reflex to time, and the state of components of the dopaminergic system in neurons in the sensorimotor cortex and caudate nucleus in rabbits were studied. Chronic administration of amphetamine increased the level of neuron spike activity and the ability to acquire and reproduce conditioned reflexes in the sensorimotor cortex, and decreased these parameters in the caudate nucleus. Biochemical studies demonstrated hyperactivation of the dopaminergic system in the caudate nucleus, as compared with the sensorimotor cortex. On the background of chronic amphetamine, haloperidol induced effects in both locations which were close to those of single doses to intact animals. The neuroleptic led to suppression of neuron activity and a decrease in the number of conditioned reactive neurons in the sensorimotor cortex, in contrast to neurons in the caudate nucleus. Short-term exposure to haloperidol produced changes in biochemical parameters towards normalization of neurotransmitter metabolism.

Effects of Neurotransplantation of Cultured Human Neural and Mesenchymal Stem Cells on Learning and the State of the Brain in Rats after Hypoxia

The effects of neurotransplantation of cultures of neural stem cells (NSC) and mesenchymal stem cells (MSC) on learning in rats subjected to acute hypoxia and the status of their brains were studied. The results showed that in the presence of NSC (but not MSC), there were improvements in the learning of a defensive conditioned reflex; both NSC and MSC had neuroprotective influences on the brain. NSC transplants demonstrated all cell types – stem/progenitor cells, neurons, and glial cells, on day 20 post-transplantation; at 10 days, MSC consisted of fibroblast-like cells, which were completely eliminated by 20 days. The effects of NSC may be associated both with their good survival and neural differentiation and with trophic influences on the recipient brain, while the effects of MSC could only be explained in terms of their trophic influences at different stages after transplantation.

Effects of the Serotonin Precursor 5-Hydroxytryptophan and the Neurotoxic Analog 5,7-Dihydroxytryptamine on the Formation of a Conditioned Defensive Reflex in the Common Snail

We report here our studies on the effects of the metabolic serotonin precursor 5-hydroxytryptophan and the neurotoxic analog 5,7-dihydroxytryptamine on the acquisition of a conditioned defensive reflex and post-training electrophysiological parameters of defensive behavior command neurons in snails. Injections of 5-hydroxytryptophan into snails via the sinus node led to acceleration of the acquisition of the conditioned defensive reflex. Snails injected with 5,7-dihydroxytryptamine did not form the conditioned reflex; subsequent injection of 5- hydroxytryptophan prevented this blockade. While 5-hydroxytryptophan prevented the action of 5,7-dihydroxytryptamine at the behavioral level, no such effect was seen at the level of the electrical properties of command neurons.

The influence of agonists of GABAA and GABAB receptors on the formation of the defensive and inhibitory conditioned reflexes

The influence of agonists of GABAA and GABAB receptors on the formation of the defensive and inhibitory conditioned reflexes

Effect of Neuroleptic Haloperidol, L-DOPA Precursor Dopamine, and Neurotoxic Dopamine Analog 6-OHDA on Acquisition of Conditioned Defensive Reflex in Edible Snail

The effect of neuroleptic haloperidol, a dopamine precursor L-DOPA, and dopamine analog 6-OHDA on the development of conditioned defensive reflex was studied in edible snails. Injection of L-DOPA to intact snails and to snails pretreated with 6-OHDA 2 h before learning session decelerated acquisition of the conditioned reflex and exerted a toxic action. In contrast, injection of 6-OHDA or haloperidol did not affect acquisition of the conditioned reflex.

Electrophysiological Studies of the Effects of Chronic Administration of Caffeine on the Formation of a Conditioned Defensive Reflex in the Common Snail

Chronic administration of caffeine to common snails increased the rate of formation of a conditioned defensive reflex. When daily caffeine injections were given immediately after the training procedure, the conditioned defensive reflex was acquired more quickly than when caffeine injections were given before the training procedure started. Chronic caffeine administration to both trained and untrained snails led to depolarization changes in the membrane potential and reductions in the threshold potential of defensive behavior command neurons in common snails. Comparative studies showed that addition of caffeine to the solution bathing the mollusk nervous system resulted in decreases in the threshold potential of command neurons in both intact and trained snails; there was, however, no change in the membrane resting potential.

Relationship between the types of behavioral reaction in a conditioned shake-off reflex and neocortical lateralization

The nature of the spike activity and interhemisphere interactions of neurons in the parietal cortex (somatosensory representation of the ear) during the intersignal period before active shake-off and passive (freezing) reactions to stimuli was studied in rabbits after acquisition of a conditioned defensive escape reflex. Before passive reactions, in contrast to the situation before active shake-off, there were increases in right-sided influences on cells in the left hemisphere with delays of up to 100 msec, leading to asymmetry in interhemisphere interactions with right-sided dominance. Passive reactions were preceded by increases in the extent of frequencies in the delta range in the spike activity of individual neurons and in interactions between pairs of cells. These data provide evidence that the existence and nature of interhemisphere asymmetry before stimulation is one of the factors determining the passive or active type of behavioral reaction and reflecting the level of activation of the cortex.

Effects of β-amyloid (25–35) on learning in the common snail

The effects of neurotoxic beta-amyloid fragment (25-35) on the formation of behavioral sensitization and a conditioned defensive reflex to food were studied. Administration of beta-amyloid (25-35) to common snails before the start of training led to a significant reduction in sensitization of the defensive reaction, weakening of the formation of the conditioned defensive reflex to food, and impairment of memory. These impairments to behavioral plasticity may be mediated by changes in synaptic plasticity previously observed in the presence of beta-amyloid.

Local changes in the redox potential in the rabbit cerebral cortex accompanying the acquisition of a conditioned defensive reflex

The oxidative-reductive (redox) potential (E) of brain tissue depends on the ratio of the speeds of processes occurring in the glycolysis (the evolutionarily ancient energy compartment operating without oxygen) and oxidative metabolism (evolutionarily younger and energetically more efficient) compartments. E in the cortex was recorded using implanted platinum electrodes. A conditioned defensive reflex (CDR) was developed by combination of a light and electrocutaneous stimulation (ECS) of the ear. The results showed that after a series of combinations of the light and the ECS, the light started to elicit a change in E. By 200 combinations, the brain developed both increases and decreases in E during combinations. As the number of combinations increased, increases in E were gradually replaced by decreases. We believe that this dynamic of the balance of the major sources of brain energy supply suggests that formation of the CDR may involve a significant role for subcellular structures receiving energy from oxidative metabolism formed at the relatively young evolutionary level, while the major source of energy for brain function during performance of the acquired CDR is the older evolutionary compartment - glycolysis.

Influences of an acoustic signal with ultrasound components on the acquisition of a defensive conditioned reflex in Wistar rats

The effects of short (90 sec) exposures to a complex acoustic signal with ultrasound components on the acquisition of a defensive conditioned two-way avoidance reflex using an electric shock as the unconditioned stimulus in a shuttle box were studied in female Wistar rats. This stimulus induced audiogenic convulsions of different severities in 59% of the animals. A scale for assessing the ability of rats to acquire the conditioned two-way avoidance reflex was developed. Presentation of the complex acoustic signal was found to be a powerful stressor for Wistar rats, preventing the acquisition of the reflex in the early stages (four and six days) after presentation. This effect was independent of the presence and severity of audiogenic convulsions in the rats during presentation of the acoustic signal. On repeat training nine days after the acoustic signal (with the first session after four days), acquisition of the reflex was hindered (as compared with controls not presented with the acoustic signal). However, on repeat training at later time points (1.5 months after the complex acoustic signal, with the first session after six days), the rats rapidly achieved the learning criterion (10 correct avoidance responses in a row). On the other hand, if the acoustic signal was presented at different times (immediately or at three or 45 days) after the first training session, the animals' ability to acquire the reflex on repeat training was not impaired at either the early or late periods after exposure to the stressor. These results suggest that the complex acoustic signal impairs short-term memory (the process of acquisition of the conditioned two-way avoidance reflex at the early post-presentation time point) but has no effect on long-term memory or consolidation of the memory trace.