Analysis of the process of learning in the formation of the conditioned reflex of avoidance in rats

During acquisition of avoidance conditioned reflex (CR) in shuttle box by electric shock it is shown that the performance of that defence reaction is induced by the joint action of two factors: general arousal of animals and motivation. Motor activity of rats in an "open field", the number of short-latency (2s) and intersignal responses during formation of the avoidance CR are in index of the general arousal of rats. An artificial increase in the general arousal of animals by caffeine induces acceleration of CR performance. A constant level of the general arousal of rats is one of the reasons that oxytocin does not influence the rate and dynamics of the avoidance CR performance in rats.     

The characteristics of shuttle avoidance learning in spontaneously hypertensive and normotensive rats]

In spontaneously hypertensive (strain SHR) and normotensive (strain WKY) rats was studied the elaboration of conditioned reflex of active avoidance in shuttle box. In case when the shuttle box was divided by a partition the SHR rats learned worse than WKY rats. In shuttle chamber without partition the SHR rats, on the contrary, learned better that WKY ones. Such character of interlinear differences can be connected with properties of formation of the instrumental habit of deliverance from electropainful stimulus, because the presence of partition significantly hampered its fulfillment. The obtained results, compared with literature data, testify to the fact that differences of SHR and WKY rats in elaboration of conditioned reflexes are explained basically by the properties of their unconditioned activity and not of the associative processes.     

Genotype-environment interaction in passive avoidance learning of the paradise fish (Macropodus opercularis)

Passive dark avoidance conditioning and effects of the presence and absence of a fish-like dummy on the training process were studied in four inbred strains of paradise fish. Strain differences were found in the shuttle activity during habituation trials, and in the sensitivity to the mild electric shock punishment. The presence or absence of the dummy in the punished dark side of the shuttle box had a genotype-dependent effect on the measures taken during the conditioning process. The statistical analysis of the learning curves revealed differences in the way the strains varied in the different environments, i.e. genotype--environment interaction components of variances were identified. The results are discussed in the light of previous investigations and their implication in further genetic analysis.     

NF-kappaB regulates the expression of the human complement receptor 2 gene

CR2 is a key regulator of the B cell response to Ag. Here we show that NF-kappaB enhances the expression of the human CR2 gene. Promoter truncation, deletion, and mutagenesis studies indicated a functional role for a consensus NF-kappaB promoter element, as well as a heterogeneous nuclear ribonucleoprotein D element and an overlapping X box/E box. By supershift analysis, the first two elements bound NF-kappaB p50 and p65 and heterogeneous nuclear ribonucleoprotein RNP D, respectively. The X box/E box bound regulatory factor X5 and, surprisingly, NF-kappaB p50 and p65. Overexpression of NF-kappaB p50 enhanced the activity of the CR2 promoter in B cell lines and primary B cells, suggesting a direct role for NF-kappaB in regulating promoter activity. Importantly, mutation of the NF-kappaB element or the X box/E box rendered the promoter unresponsive to NF-kappaB p50. Using chromatin immunoprecipitation in live B cell lines and primary B cells, we found that NF-kappaB proteins p50, p65, and c-Rel bound to the genomic promoter at two locations that overlap with the consensus NF-kappaB element or the X box/E box. Finally, stimuli that activate NF-kappaB enhanced the activity of the CR2 promoter, and LPS rapidly increased the number of CR2 proteins on the surface of primary B cells. We propose that the NF-kappaB signaling pathway enhances the expression of the CR2 gene, as a result of NF-kappaB proteins binding to two CR2 promoter elements. Thus, at the onset of an infection, LPS could sensitize the B cell to Ag by enhancing the level of CR2-costimulatory molecules on the cell surface.     

A comparison of the self-stimulation reaction and of conditioned place preference with fenamine administration in rats]

The reinforcing properties of different doses of amphetamine (1 and 5 mg/kg) were examined using two variants of self-stimulation reaction (in the Skinner box and locomotor self-stimulation in a shuttle box) and place preference test. Amphetamine in dose of 1 mg/kg increased the frequency of self-stimulation in the Skinner box and prolonged the time of rat staying in active zone of a shuttle box to a greater degree than 5 mg/kg of the drug. On the contrary, the aversive phase of self-stimulation, determined by a coefficient of "disagreement", grew higher after 5 mg/kg amphetamine than following 1 mg/kg. The study of effects by place preference test revealed the other regularity: the most positive reinforcing properties possessed the drug in a dose of 5 mg/kg. Thus, there are dissociation between the two doses of amphetamine (1 and 5 mg/kg) in their action on different physiological conditioned responses. The mechanisms of this dissociation are discussed.     

The ACTH-(4-9) analog ORG 2766 and desglycinamide9-(Arg8)-vasopressin reverse the retrograde amnesia induced by disrupting circadian rhythms in rats

Disrupting circadian organization by exposing rats to a shifted illumination schedule after training for passive avoidance and shuttle box avoidance behavior resulted in retrograde amnesia as evidenced by impaired performance during retention and extinction testing respectively. A single treatment with either the ACTH-(4-9) analog ORG 2766 or desglycinamide9-(Arg8)-vasopressin (DGAVP) 1 hour prior to the retention of passive avoidance or extinction of shuttle box avoidance behavior restored the behavioral impairment. It is suggested that these peptides may be useful to relieve memory deficits induced by disturbances in circadian organization.     

Effect of 2450 MHz microwave exposure on behavioural thermoregulation in mice

1. 1.|The purpose of this study was to determine the threshold specific absorption rate (SAR) during exposure to 2450 MHz continuous wave (CW) microwaves that affected thermoregulatory behaviour in mice.

2. 2.|A Plexiglas shuttle box was placed inside a waveguide imposed with a temperature gradient. The temperature gradient allowed the mice to select a particular section of the shuttle box which was, presumably, related to their state of thermal comfort. Exposing the mice to 2450 MHz inside the waveguide at SARs of 0–5.3 W kg⁻¹ for 1 h caused no significant change in their preferred ambient temperature.

3. 3.|Increasing SAR from 5.3 to 18.1 W kg⁻¹ caused the animals to shift their position to the cooler end of the shuttle box.

4. 4.|Following termination of microwave exposure animals that had selected a cool ambient temperature returned to the warm side of the shuttle box.

5. 5.|It is concluded that for mice exposed to radiation at 2450 MHz the thermoregulatory behaviour is significantly affected at SARs of 5.3 to 9.9 W kg⁻¹.

The effect of stimulation and blockade of the dopaminergic system on the choice of behavioral strategy by rats in the shuttle box]

Upon stimulation and blockade of dopaminergic system of rats in the shuttle box the correlation between the strategy of escape behavior and functional state of dopaminergic system has been found. The modulatory effect of these systems on the mechanism of the adequate choice is suggested.     

Enhanced conjugative transfer of plasmid DNA from Escherichia coli to Staphylococcus aureus and Listeria monocytogenes

Abstract Transfer of mobilizable shuttle cloning vectors by conjugation from Escherichia coli to Staphylococcus aureus occurred at a very low frequency (10⁻⁹ transconjugants per donor colony-forming unit after the mating period). It was observed that subinhibitory concentrations of penicillins (oxacillin or penicillin G) in the mating medium resulted in increased transfer frequency by conjugation of the shuttle vector pAT18 from E. coli SM10 to S. aureus 80CR5 Str (54-fold) and to Listeria monocytogenes LO17RF (45-fold). These results were interpreted as indicating that the cell wall of Gram-positive bacteria constitutes an important barrier for conjugative transfer of genetic information demonstrated that presence of a restriction system(s) in S. aureus recipients represented a major barrier to introduction of foreign DNA.     

Behavioral characteristics in mice with brain lesions induced by hypertonic saline

Behavioral and histopathological characteristics were studied in mice treated repeatedly with hypertonic saline. In passive avoidance response using a step-through-type shuttle box, the mice treated with hypertonic saline showed shorter latency than control mice. No changes were observed in active avoidance response using a two-way-type shuttle box, spontaneous motor activity or motor function. Histopathological examination revealed marked and frequent degeneration and loss of neurons in the hippocampus as compared with animals after single treatment. The animals with severe hippocampal lesions showed impairment of passive avoidance response. The present brain lesions resulting from repeated treatment with hypertonic saline in mice are considered to be a possible model for memory disorders caused by hippocampal lesions in humans.     

Analysis of the striato-pallidal interactions in regulation of avoidance behavior

Impairment of avoidance conditioning in the shuttle box was found in rats with bicuculline intrapallidal administration, as well as activation of the conditioning and stereotyped movements during amphetamine intrastriatal administration. These neuropharmacological effects upon both ganglia areas induced dynamic behavioural changes in the avoidance conditioning and open-field locomotor activity. The findings suggest involvement of neostriatalpallidal relationship in control of avoidance conditioning and complex behavioural acts.     

Behavioral reactions to stimulation of the emotiogenic zones of the brain in the rats with different individual experience

Emotional reactions evoked by electric stimulation of the hypothalamus and amygdala were studied in white outbred rats, grown either in conditions of isolation or in community. The method of self-stimulation in shuttle box was used. The values of self-stimulation reaction were significantly lower and those of avoidance reactions were higher in animals bred in isolation. Their food-procuring behaviour disappeared faster at stimulation of the negative emotiogenic zones. The observed differences are due to plastic reorganization of the brain reinforcing systems.     

Phenylacetate and the enduring behavioral deficit in experimental phenylketonuria

Phenylacetate, a metabolite derived from phenylalanine, is clearly associated with brain dysfunction in simulated phenylketonuria. Injections of phenylacetate, phenylethylamine, or p-chlorophenylalanine + L-phenylalanine, all yielding similar concentrations of phenylacetate in the rat brain during post-natal development, induced similar behavioral deficits: hypoactivity in an open field and poor performance in both a water maze and shuttle box. In contrast, animals treated with the other major metabolites of phenylalanine, phenylpyruvate, phenyllactate and mandelate, during the same developmental period displayed normal behavior.     

Plasmid profile and construction of a small shuttle vector in <Emphasis Type="Italic">Laribacter hongkongensis</Emphasis>

Among 21 human strains of Laribacter hongkongensis, small plasmids were observed in four strains, and large ones in six strains. The smallest, 3264-bp plasmid, pHLHK19, has only one ORF that encodes a putative replication initiator protein and a predicted origin of replication (ori) with a DnaA box, three 18-bp direct repeats and five pairs of inverted repeats. An Escherichia coli-L. hongkongensis shuttle vector was constructed by ligating the HindIII-digested pHLHK19, containing the replication initiator protein and ori of pHLHK19, to HindIII-digested pBK-CMV. This shuttle vector can propagate in E. coli and L. hongkongensis with good transformation efficiencies.     

The differences between sexes and strains in the capacity to acquire a passive avoidance conditioned reflex in KLA- and KHA-strain rats

The interstrain differences in passive avoidance conditioning were studied in male and female KHA (Koltushi High Avoidance) and KLA (Koltushi Low Avoidance) rats. These strains were selected for the rate of acquisition of active avoidance in a shuttle box. It was shown that the passive avoidance was substantially better acquired in the KLA strain than in the KHA. In females KHA rats the capability for passive avoidance conditioning depended on the estrus phase: the conditioning was impossible in proestrus.