Bar Press Research Articles

The Effect of Adhesive Ratio on the Quality of Charcoal Briquettes

This study used cassava stem charcoal and charcoal from forest fires mixed with tapioca adhesive at different ratios, the aim was to analyze the effect of different adhesive ratios on the quality of charcoal briquettes.Charcoal briquettes are formed using a 40 bar press machine with a pressing time of 10 minutes. The mixture of charcoal briquette raw materials uses a tapioca adhesive ratio of 2%, 4%, 6%, 8% and 10%.Testing is carried out to determine the quality, then analyzed and compared with the SNI 01-6235-2000 standard.The effect of adhesive ratio on adhesive quality was analyzed using a Completely Randomized Design (CRD). The test results show the following values:density 0.54 g/cm3, moisture content 4.97%, compressive strength 28.43 kg/cm2, volatile matter content 36.02%, ash content 6.36%, fixed carbon content 56.45% and calorific value 6,195 cal/gobtained from a 10% adhesive ratio. The adhesive ratio has a very significant effect on the water content, compressive strength and calorific value; has a significant effect on the density value; and has no significant effect on the volatile matter value, ash content and bound carbon content.The results of charcoal briquette testing mostly meet the standards according to SNI (No. 01-6235-2000)

Neural decoding and feature selection methods for closed-loop control of avoidance behavior

Objective.Many psychiatric disorders involve excessive avoidant or defensive behavior, such as avoidance in anxiety and trauma disorders or defensive rituals in obsessive-compulsive disorders. Developing algorithms to predict these behaviors from local field potentials (LFPs) could serve as the foundational technology for closed-loop control of such disorders. A significant challenge is identifying the LFP features that encode these defensive behaviors.Approach.We analyzed LFP signals from the infralimbic cortex and basolateral amygdala of rats undergoing tone-shock conditioning and extinction, standard for investigating defensive behaviors. We utilized a comprehensive set of neuro-markers across spectral, temporal, and connectivity domains, employing SHapley Additive exPlanations for feature importance evaluation within Light Gradient-Boosting Machine models. Our goal was to decode three commonly studied avoidance/defensive behaviors: freezing, bar-press suppression, and motion (accelerometry), examining the impact of different features on decoding performance.Main results.Band power and band power ratio between channels emerged as optimal features across sessions. High-gamma (80-150 Hz) power, power ratios, and inter-regional correlations were more informative than other bands that are more classically linked to defensive behaviors. Focusing on highly informative features enhanced performance. Across 4 recording sessions with 16 subjects, we achieved an average coefficient of determination of 0.5357 and 0.3476, and Pearson correlation coefficients of 0.7579 and 0.6092 for accelerometry jerk and bar press rate, respectively. Utilizing only the most informative features revealed differential encoding between accelerometry and bar press rate, with the former primarily through local spectral power and the latter via inter-regional connectivity. Our methodology demonstrated remarkably low training/inference time and memory usage, requiring<310 ms for training,<0.051 ms for inference, and 16.6 kB of memory, using a single core of AMD Ryzen Threadripper PRO 5995WX CPU.Significance.Our results demonstrate the feasibility of accurately decoding defensive behaviors with minimal latency, using LFP features from neural circuits strongly linked to these behaviors. This methodology holds promise for real-time decoding to identify physiological targets in closed-loop psychiatric neuromodulation.

Neural Decoding and Feature Selection Techniques for Closed-Loop Control of Defensive Behavior.

Many psychiatric disorders involve excessive avoidant or defensive behavior, such as avoidance in anxiety and trauma disorders or defensive rituals in obsessive-compulsive disorders. Developing algorithms to predict these behaviors from local field potentials (LFPs) could serve as foundational technology for closed-loop control of such disorders. A significant challenge is identifying the LFP features that encode these defensive behaviors. We analyzed LFP signals from the infralimbic cortex and basolateral amygdala of rats undergoing tone-shock conditioning and extinction, standard for investigating defensive behaviors. We utilized a comprehensive set of neuro-markers across spectral, temporal, and connectivity domains, employing SHapley Additive exPlanations for feature importance evaluation within Light Gradient-Boosting Machine models. Our goal was to decode three commonly studied avoidance/defensive behaviors: freezing, bar-press suppression, and motion (accelerometry), examining the impact of different features on decoding performance. Band power and band power ratio between channels emerged as optimal features across sessions. High-gamma (80-150 Hz) power, power ratios, and inter-regional correlations were more informative than other bands that are more classically linked to defensive behaviors. Focusing on highly informative features enhanced performance. Across 4 recording sessions with 16 subjects, we achieved an average coefficient of determination of 0.5357 and 0.3476, and Pearson correlation coefficients of 0.7579 and 0.6092 for accelerometry jerk and bar press rate, respectively. Utilizing only the most informative features revealed differential encoding between accelerometry and bar press rate, with the former primarily through local spectral power and the latter via inter-regional connectivity. Our methodology demonstrated remarkably low time complexity, requiring <110 ms for training and <1 ms for inference. Our results demonstrate the feasibility of accurately decoding defensive behaviors with minimal latency, using LFP features from neural circuits strongly linked to these behaviors. This methodology holds promise for real-time decoding to identify physiological targets in closed-loop psychiatric neuromodulation.

Bar press durations as a reliable and robust measure of frustration-related operant behavior: Sensitivity to incentive downshift and dose-response paradigms.

In humans, frustrating experiences are known to trigger relapse events and individuals with higher frustration intolerance show increased risk of developing substance use disorders (SUDs). Despite this clear relationship, frustration-related behavior is seldom studied concurrently with self-administration behavior in rodent models. A major obstacle has been the lack of robust, quantitative assays of frustration-related operant behavior thus far. In previous work, we identified increased bar press (BP) durations in response to frustrating conditions in rats self-administering natural or drug rewards. Here, to propose BP durations as a measure of frustration-related behavior, we conducted an operant successive negative contrast (oSNC) study and found that increases in BP durations are observed in the absence of increased effort, providing evidence that this is a psychological phenomenon. Moreover, we assess the viability of widespread use of BP duration measurements as a behavioral tool by quantifying performance as it pertains to sensitivity, robustness, replicability, and sex differences. We conclude that increases in BP durations are a highly sensitive psychological response to frustrating conditions and that this measure is robust, replicable, and applicable to both sexes.

Optimization of a High Capacity Industrial Bar Press for Jatropha Curcas Oil Extraction

This study allowed us to achieve the optimal yield for the extraction of Jatropha Curcas oil from the main operating variables of an industrial press. We used an industrial bar press with a large extraction capacity to carry out this work. Two interesting and indicative parameters on the influence of the efficiency of the press have been analyzed, namely the number of steps of screw and the no-load temperature on the efficiency, the temperatures of the screw, oil and cake, the flow rate of the press, the power, the specific mechanical energy of the press. The best result of 31.09%, which corresponds to the maximum recovery rate of 76.92%, was obtained with the highest number of steps of screw and the highest no-load temperature. The influence of the no-load temperature of the screw on the stability of the press has also been highlighted. The screw, the oil and the cake temperatures stabilize when the no-load temperature is greater than or equal to 100°C. The study of operating variables shows their role on the specific mechanical energy. Indeed, the increase in the number of steps of screw from 4 to 6 results in a decrease in seed flow and increase in power leading to an increase in the specific mechanical energy from 34.01 to 49.83 Wh/kg.

Quantifying defensive behavior and threat response through integrated headstage accelerometry

BackgroundDefensive and threat-related behaviors are common models for aspects of human mental illness.These behaviors are typically quantified by potentially laborious and/or computationally intensive video recording and post hoc analysis. Depending on the analysis method, the resulting measurements can be noisy or inaccurate. Other defensive behaviors, such as suppression of operant reward seeking, require extensive animal pre-training. Inertial tracking and accelerometry can be computationally efficient, but require specialized hardware. New methodWe quantified rodent defensive behavior using a commercially available electrophysiology headstage with 3-axis accelerometry integration during a threat conditioning and extinction paradigm. We tested multiple pre-processing and smoothing methods and correlated them against video-derived freezing and suppression of operant bar pressing. ResultsThe best approach to tracking defensive behavior from accelerometry was Gaussian filter smoothing of the first derivative. Behavior scores from this method reproduced canonical conditioning and extinction curves. Timepoint-to-timepoint correlations between accelerometry,video, and bar press metrics were statistically significant but modest (largest r = 0.53, between accelerometry and bar press). These increased when traditional thresholding-based analyses were used, at the cost of a loss of temporal resolution (r = 0.97 between thresholded accelerometry and percent time freezing). Comparison with existing methodsAccelerometry’s integration with standard electrophysiology systems and relatively light weight signal processing may make it particularly well suited to detect behavior in resource-constrainedor real-time applications. ConclusionsAccelerometry allows researchers already using electrophysiology to assess defensive behaviors without the need for additional behavioral measures or video. The modest correlations between metrics suggest that each measures a distinct aspect of defensive behavior. Accelerometry is a viable alternative to current defensive measurements, and its non-overlap with other metrics may allow for more sophisticated dissection of threat responses.

Lever-press duration as a measure of frustration in sucrose and drug reinforcement.

Currently there is little research into the role of frustration in substance use disorders despite research showing that frustration tolerance in humans is associated with a lower likelihood of developing substance use problems, better outcomes in recovery, and fewer relapses. In order to address this need, our studies use a rat model to focus on frustration-related behavior in natural reward and addiction-related behavioral procedures. Frustration is defined as when a subject is unable to achieve a reinforcer, receives less of a reinforcer than anticipated, or has to work harder to achieve a reinforcer. In these studies, bar-press durations increase when rats are in a state of frustration during self-administration of sucrose, fentanyl, or cocaine. These data also show that average bar-press durations do not correlate with the number of bar presses, meaning that press duration is an independent measurement that represents a behavioral construct distinct from craving, which is typically measured with number of bar presses. Essentially, these results support that bar press durations can be used as a real-time measure of frustration as a 4th major facet of addiction-related behavior, adding to craving, impulsivity, and habit.

Partial Predictability in Avoidance Acquisition and Expression of Wistar-Kyoto and Sprague-Dawley Rats: Implications for Anxiety Vulnerability in Uncertain Situations.

Individual differences or vulnerabilities must exist which bias some individuals toward psychopathology while others remain resilient in the face of trauma. Recent work has studied the effects of uncertainty on individuals expressing behavioral inhibition (BI). The current study extended this work with uncertainty to Wistar Kyoto (WKY) rats which are a behaviorally inhibited inbred strain that models learning vulnerabilities for anxiety disorders and posttraumatic stress disorder (PTSD). WKY rats exhibit superior avoidance performance in a signaled bar press avoidance task in which a tone conditioned stimulus (CS) signals a foot shock unconditional stimulus (US) when compared with non-inhibited Sprague-Dawley (SD) rats. In addition, WKY rats express enhanced eyeblink conditioning. Recent work with behaviorally inhibited humans has indicated that this enhanced eyeblink conditioning is more evident in conditions that insert CS- or US-alone trials into CS-US paired training, resulting in uncertain and suboptimal learning conditions. The current study examined the effects of partial predictability training, in which the CS signaled the US only one-half of the time, on the acquisition and expression of avoidance. Standard training with a fixed 60-s CS which predicted shock on 100% of trials was compared with training in which the CS predicted shock on 50% of trials (partial predictability) using a pseudorandom schedule. As expected, WKY rats acquired avoidance responses faster and to a greater degree than SD rats. Partial predictability of the US essentially reduced SD rats to escape responding. Partial predictability also reduced avoidance in WKY rats; however, adjusting avoidance rates for the number of potential pairings of the CS and US early in training suggested a similar degree of avoidance expression late in the last session of training. Enhanced active avoidance expression, even in uncertain learning conditions, can be interpreted as behaviorally inhibited WKY rats responding to the expectancy of the shock by avoiding, whereas non-inhibited SD rats were responding to the presence of the shock by escaping. Future work should explore how WKY and SD rats as well as behaviorally inhibited humans acquire and extinguish avoidance responses in uncertain learning situations.

Modeling Interval Timing by Recurrent Neural Nets.

The purpose of this study was to take a new approach in showing how the central nervous system might encode time at the supra-second level using recurrent neural nets (RNNs). This approach utilizes units with a delayed feedback, whose feedback weight determines the temporal properties of specific neurons in the network architecture. When these feedback neurons are coupled, they form a multilayered dynamical system that can be used to model temporal responses to steps of input in multidimensional systems. The timing network was implemented using separate recurrent “Go” and “No-Go” neural processing units to process an individual stimulus indicating the time of reward availability. Outputs from these distinct units on each time step are converted to a pulse reflecting a weighted sum of the separate Go and No-Go signals. This output pulse then drives an integrator unit, whose feedback weight and input weights shape the pulse distribution. This system was used to model empirical data from rodents performing in an instrumental “peak interval timing” task for two stimuli, Tone and Flash. For each of these stimuli, reward availability was signaled after different times from stimulus onset during training. Rodent performance was assessed on non-rewarded trials, following training, with each stimulus tested individually and simultaneously in a stimulus compound. The associated weights in the Go/No-Go network were trained using experimental data showing the mean distribution of bar press rates across an 80 s period in which a tone stimulus signaled reward after 5 s and a flash stimulus after 30 s from stimulus onset. Different Go/No-Go systems were used for each stimulus, but the weighted output of each fed into a final recurrent integrator unit, whose weights were unmodifiable. The recurrent neural net (RNN) model was implemented using Matlab and Matlab’s machine learning tools were utilized to train the network using the data from non-rewarded trials. The neural net output accurately fit the temporal distribution of tone and flash-initiated bar press data. Furthermore, a “Temporal Averaging” effect was also obtained when the flash and tone stimuli were combined. These results indicated that the system combining tone and flash responses were not superposed as in a linear system, but that there was a non-linearity, which interacted between tone and flash. In order to achieve an accurate fit to the empirical averaging data it was necessary to implement non-linear “saliency functions” that limited the output signal of each stimulus to the final integrator when the other was co-present. The model suggests that the central nervous system encodes timing generation as a dynamical system whose timing properties are embedded in the connection weights of the system. In this way, event timing is coded similar to the way other sensory-motor systems, such as the vestibulo-ocular and optokinetic systems, which combine sensory inputs from the vestibular and visual systems to generate the temporal aspects of compensatory eye movements.

Different periods of forced abstinence after instrumental learning for food reward of different macronutrient value on responding for conditioned cues and AMPAr subunit levels

Food craving can be viewed as an intense desire for a specific food that propagates seeking and consuming behavior. Prolonged forced abstinence from rewarding foods can result in escalated food-seeking behavior as measured via elevated responding for food-paired cues in the absence of the primary reward. Palatable food consumption and food-seeking is associated with changes in the abundance and composition of AMPA receptors in the nucleus accumbens (NAc) but differing results have been reported. The present study examined whether different food types could produce escalated food-seeking behavior after various abstinence periods and whether this was associated with changes in AMPA receptor protein levels. Rats were trained for 10 days to bar press for purified, sucrose, or chocolate-flavored sucrose pellets. Rats were tested at 24 hrs, 7 d or 14 d whereby bar pressing resulted in presentation of cues paired with food but no food reward was delivered. Western blotting was used to determine protein levels of GluR1, GluR1pSer845, and GluR2 in the NAc. Three separate groups were assessed: 1) a group that was trained on the operant task and tested for conditioned responding (tested group); 2) a group that was trained on the operant task but not tested (non-tested group); 3) a group that was neither trained nor tested (control). The purified food group showed a time-dependent elevation in conditioned bar pressing over the 3 abstinence periods. GluR1 AMPAr subunit levels were higher in the purified and sucrose groups tested at 24 hours compared to the non-tested and control values. GluR1 levels subsequently declined at the 7- and 14-day abstinence periods in the purified and sucrose tested and non-tested groups compared to control values. GluR2 and pSer845 Glur1 levels were similar across all groups and abstinence periods. These results show that food-seeking behavior associated with forced abstinence from different food rewards may depend on the macronutrient composition of the food reward or the food type given during the abstinence period. A clear link with AMPAr subunit levels in this model was not established.

Comparison of the Time-Dependent Changes in Immediate Early Gene Labeling and Spine Density Following Abstinence From Contingent or Non-contingent Chocolate Pellet Delivery.

Rationale: Incubation of craving is a phenomenon whereby responding for cues associated with a reward increases over extended periods of abstinence. Both contingent and non-contingent behavioral designs have been used to study the incubation of craving phenomenon with differing results. The present study directly compares behavioral and neural changes following contingent or non-contingent administration of chocolate flavored pellets.Objective: The current study examined whether an incubation of craving response would be observed at the behavioral and neural levels following delays of abstinence from chocolate pellets in a contingent or non-contingent reinforcement design.Methods: Rats were trained for 10 days to bar press for chocolate pellets (contingent) or received chocolate pellets in a non-contingent design (classical conditioning). Groups were then subjected to abstinence from the reward for 24 h, 7, 14 or 28 days at which point they were tested for responding for reward associated cues. Following the test, brains from all rats were processed and assessed for c-Fos and FosB labeling as well as dendritic spine density in the nucleus accumbens (NAc).Results: Behavioral measures during the test (lever presses, food hopper entries and locomotor activity) revealed similar behavioral outcomes across all delays indicating the lack of an incubation of craving response on both the contingent and non-contingent designs. Overall, labeling of c-Fos in the NAc was lower for the non-contingent group compared to the operant-trained and food restricted control. Compared to the operant-trained and non-trained control groups, a significantly reduced FosB labeling was noted in the NAc of the classically conditioned groups across all abstinence periods. Spine density in the NAc was elevated in both the classically and operant conditioned compared to the food-restricted, non-trained controls.Conclusions: Chocolate pellet reward did not result in incubation of craving but did produce behavioral learning that was associated with increased spine density. This suggests that chocolate pellet administration results in long-term structural and functional changes that are present for at least 28 days following abstinence. Contingent and non-contingent administration resulted in differential immediate early gene labeling in the NAc, but the functional significance of this has yet to be elucidated.

Preadolescent Phthalate (DEHP) Exposure Is Associated With Elevated Locomotor Activity and Reward-Related Behavior and a Reduced Number of Tyrosine Hydroxylase Positive Neurons in Post-Adolescent Male and Female Rats.

Phthalate administration to male rats has been shown to negatively impact neural development while development of the female rat brain is less affected. Because a number of exogenous agents have been shown to interfere with dopamine function, we evaluated post-adolescent behavioral (operant conditioning for food reward and locomotor activity), histological (tyrosine hydroxylase; TH), and genetic (mRNA levels) outcomes of preadolescent (postnatal days [PND] 16-22) phthalate exposure. Male and female Long-Evans rats were administered 4 doses (0, 1, 10, or 20 mg/kg) of di-(2-ethylhexyl)phthalate (DEHP) i.p. from PND16 to 22. Rats were trained on an operant task to bar press for chocolate-flavored pellets from PND55-63 then euthanized on PND78. The 10 mg/kg DEHP dose was associated with elevated bar pressing for food reward during acquisition and extinction while the 20 mg/kg dose was associated with elevated locomotor activity in both males and females. Stereological analysis revealed reduced TH+ densities in the SNc in DEHP- (10 and 20 mg/kg) treated male and female rats. In the VTA, TH+ staining was reduced in male rats treated with 10 or 20 mg/kg DEHP while in females, the TH: CV ratio was higher at the 10 mg/kg dose compared with controls. An examination of Th mRNA showed a main effect of sex with females showing increased Th expression at all DEHP doses. The present results show that preadolescent phthalate exposure results in detrimental dopaminergic system development impacting neurobehavioral function in post-adolescent rats.

INTERAÇÕES COMPORTAMENTAIS EM ESQUEMA MÚLTIPLO UTILIZANDO O JATO DE AR QUENTE (JAQ) COMO ESTÍMULO PUNIDOR

Interação comportamental é um fenômeno que pode ocorrer em esquemas múltiplos, em que a taxa de respostas em um componente pode mudar em função de alteração do esquema de reforçamento ou de punição no segundo componente. Interações comportamentais podem ocorrer quando há utilização de contingências apetitivas ou aversivas, como punição. Com relação às contingências punitivas, existem dados conflitantes na literatura sobre a produção de contraste ou indução com não humanos, utilizando majoritariamente choque elétrico como estímulo punidor. O objetivo deste estudo foi verificar se ocorreria algum tipo de interação comportamental em esquemas múltiplos, utilizando o jato de ar quente (JAQ) como estímulo punidor. Dezesseis ratos albinos foram expostos às fases: Pré-Punição, Punição e Pós-Punição. Nas três fases vigorou um esquema múltiplo com dois componentes (claro e escuro). O esquema de reforçamento em vigor em ambos os componentes foi intervalo variável 30s (VI 30) para respostas de pressão à barra, em todas as fases. Na fase punição, o JAQ foi administrado contingente a cada resposta de pressão à barra no componente claro para metade dos sujeitos, e no escuro para a outra metade. Ocorreu indução negativa no componente não punido, para todos os sujeitos, principalmente nas sessões iniciais; ao longo das sessões, ocorreu recuperação na taxa nesse componente para todos os sujeitos, resultando em ocorrência tardia de contraste positivo para três dos sujeitos. A produção de contraste parece estar relacionada ao número de sessões de exposição ao punidor.Palavras-chave: interação comportamental, punição, contraste, indução.

Sterilization of a porous ultrahigh-molecular-weight polyethylene in supercritical Freons

The possibility of sterilization of porous ultrahigh-molecular-weight polyethylene in subcritical Freons R22 and R410a in the absence of modifiers is for the first time demonstrated. The maximum sterilization effect is achieved when sterilization with Freon R410a is performed in static conditions for 30 min at 50°С and 250 bar or with Freon R22 for 60 min at 70°С and cyclically varied pressure within 100–290 bar (press–depress mode).

The effect of repeated exposure to ethanol on pre-existing fear memories in rats.

RationaleThere is a high degree of comorbidity between alcohol use disorder and post-traumatic stress disorder (PTSD), but little is known about the interactions of ethanol with traumatic memories.ObjectivesUsing auditory fear conditioning in rats, we asked if repeated exposure to ethanol could modify the retrieval of fear memories acquired prior to ethanol exposure.MethodsFollowing auditory fear conditioning, Sprague-Dawley rats were given daily injections of ethanol (1.5 g/kg) or saline over 5 days. Two days later, they were given 20 trials of extinction training and then tested for extinction memory the following day. In a separate experiment, conditioned rats were given repeated ethanol injections and processed for c-Fos immunohistochemistry following a fear retrieval session.ResultsTwo days following the cessation of ethanol, the magnitude of conditioned fear responses (freezing and suppression of bar pressing) was significantly increased. This increase persisted the following day. Waiting 10 days following cessation of ethanol eliminated the effect on fear retrieval. In rats conditioned with low shock levels, repeated exposure to ethanol converted a sub-threshold fear memory into a supra-threshold fear memory. It also increased c-Fos expression in the prelimbic prefrontal cortex, paraventricular thalamus, and the central and basolateral nuclei of the amygdala, areas implicated in the retrieval of fear memories.ConclusionsThese results suggest that repeated exposure to ethanol may exacerbate pre-existing traumatic memories.

Persistent active avoidance correlates with activity in prelimbic cortex and ventral striatum.

Persistent avoidance is a prominent symptom of anxiety disorders and is often resistant to extinction-based therapies. Little is known about the circuitry mediating persistent avoidance. Using a recently described platform-mediated active avoidance task, we assessed activity in several structures with c-Fos immuno-labeling. In Task 1, rats were conditioned to avoid a tone-signaled shock by moving to a safe platform, and then were extinguished over two days. One day later, failure to retrieve extinction correlated with increased activity in the prelimbic prefrontal cortex (PL), ventral striatum (VS), and basal amygdala (BA), and decreased activity in infralimbic prefrontal cortex (IL), consistent with pharmacological inactivation studies. In Task 2, the platform was removed during extinction training and fear (suppression of bar pressing) was extinguished to criterion over 3–5 days. The platform was then returned in a post-extinction test. Under these conditions, avoidance levels were equivalent to Experiment 1 and correlated with increased activity in PL and VS, but there was no correlation with activity in IL or BA. Thus, persistent avoidance can occur independently of deficits in fear extinction and its associated structures.

Attenuation of MK-801-induced behavioral perseveration by typical and atypical antipsychotic pretreatment in rats.

The noncompetitive NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5-10-imine maleate (MK-801) has been shown to increase the probability of operant responding during extinction and reduce infralimbic prefrontal cortical activation, possibly modeling the cognitive dysfunction symptomology, and underlying cause, in patients with schizophrenia. The present study sought to determine if typical and/or atypical antipsychotics would attenuate the MK-801-induced behavioral perseveration and whether this would be associated with concomitant changes in phosphorylated ERK1/2 (pERK1/2) labeling in the infralimbic cortex (IL). Male, Long Evans rats were pretreated with the typical antipsychotic, Flupenthixol (0, 0.125, 0.25 or 0.5 mg/kg) or the atypical antipsychotic, aripiprazole (0, 0.3, 1.0, 3.0 mg/kg), then given 0.1 mg/kg MK-801 followed by a 60-min appetitive operant extinction session. Flupenthixol produced a dose-dependent decrease in MK-801-induced bar pressing behavior and locomotor activity and a dose-dependent increase in IL pERK1/2 labeling. Aripiprazole produced a U-shaped dose-response curve on MK-801-induced bar pressing behavior, a dose-dependent decrease in locomotor activity but no changes in IL pERK1/2 labeling. The attenuation of the MK-801-induced behavioral (bar pressing, locomotion) profile by Flupenthixol indicates a clear dopaminergic contribution to this behavior. The behavioral effect of aripiprazole may be due to its a) binding to presynaptic dopamine receptors at the midrange dose decreasing dopamine output and b) binding to postsynaptic dopamine receptors at the higher dose increasing dopamine tone. While both classes of antipsychotics can normalize perseverative behavioral symptoms, the underlying prefrontal cortical dysregulation seems to persist.

Lesions of the posterior paraventricular nucleus of the thalamus attenuate fear expression

The paraventricular nucleus of the thalamus (PVT) has generated interest because of its strong projections to areas of the brain associated with the regulation of emotional behaviors. The posterior aspect of the PVT (pPVT) is notable for its projection to the central nucleus of the amygdala which is essential for the expression of a conditioned fear response. The present study was done to determine if the pPVT is involved in the expression of fear by examining the effect of post-conditioning lesions of the pPVT. Male rats were trained to bar press for food pellets on a variable ratio schedule. Fear conditioning was done using auditory tones (30 s) that co-terminate with footschocks (0.65 mA, 1.0 s). Rats were anesthetized 24 h later and small bilateral electrolytic lesions of the pPVT were made. Fear expression to the tone was assessed using suppression of bar-pressing and freezing after one week of recovery from the surgical procedure. Small bilateral lesions of the pPVT increased bar-pressing for food and decreased freezing during the presentation of the conditioned tone. Lesions of the pPVT had no effect on fear extinction, fear conditioning to a novel tone, or the motivation for food as assessed using a progressive ratio (PR) schedule. The results of the experiment support a role for the pPVT in fear expression. In contrast, the pPVT does not appear to be involved in fear learning or extinction nor does it appear to play a role in the motivation of rats to bar press for food.

90 Intra-accumbens injection of a dopamine aptamer abates MK-801-induced cognitive dysfunction in a model of Schizophrenia

Aptamers are short, single-stranded sequences of DNA or RNA, which exhibit conformationally unique three-dimensional structures. Aptamer binding to target molecular substrates (from small molecules to proteins) demonstrates a high degree of affinity and specificity, in an analogous fashion to antigen–antibody binding. Aptamers offer several advantages over antibodies, including highly reproducible synthesis and ease of modification. Though the characteristics of aptamers and their applicability within the central nervous system show great potential, research in this area is limited. In the present work, the ability of a dopamine-binding DNA aptamer to regulate MK-801-induced cognitive deficits when injected into the nucleus accumbens was investigated. Systemic administration of the non-competitive NMDA-receptor antagonist, MK-801, has been proposed to model cognitive deficits similar to those seen in patients with schizophrenia. Rats were trained to bar press for chocolate pellet rewards then randomly assigned to receive an intra-accumbens injection of a DNA aptamer (200 nM; n = 7), tris buffer (n = 6) or a randomized DNA oligonucleotide (n = 7). Animals were then treated systemically with MK-801 (0.1 mg/kg) and tested for their ability to extinguish their bar-pressing response. Injection of 200 nM dose of the dopamine aptamer reversed this MK-801-induced elevation in lever pressing to levels as seen in rats not treated with MK-801. Tests for activity showed that the aptamer did not impair locomotor activity. Results demonstrate the in vivo utility of DNA aptamers as tools to investigate neurobiological processes in preclinical animal models of mental health disease.

AQUISIÇÃO E REVERSÃO DE DISCRIMINAÇÕES EM RATOS DESNUTRIDOS

Uma deficiência nutricional resulta em alterações morfológicas, neuroquímicas e comportamentais. O objetivo deste estudo foi avaliar a aquisição e a reversão de discriminação em ratos controles e desnutridos. As dietas contendo 16% (Controles – C) ou 6% de proteína (Desnutridos – D) foram oferecidas do nascimento até os 35 dias de idade, quando os dois grupos passaram a receber dieta comercial (recuperação alimentar para os D). Antes dos 85 dias de idade, quando foi iniciado o procedimento de discriminação, o peso corporal foi reduzido em 15% do peso ad libitum. Os estímulos discriminativos eram luz ou som: os grupos C e D foram distribuídos aleatoriamente para as condições de LUZ ou SOM. Após a modelagem da resposta de pressão à barra, as respostas passaram a ser reforçadas em esquema de razão variável (VR 12) durante o SD e extintas na ausência destes estímulos (S?). Após atingir o índice de 80 % na aquisição da discriminação, foi iniciada a reversão na função dos estímulos: as respostas passaram a ser reforçadas na ausência de LUZ ou de SOM. Os dois grupos mostraram um efeito significativo de sessões nas duas fases. Ambos os grupos, D e C, aprenderam as discriminações, chegando a índices de discriminação superiores a 80%, mas não foram observados efeitos de dieta nem de estímulo. A única diferença a ser apontada foi uma tendência de desempenho melhor na condição de SD LUZ do que em SOM, embora não tenham sido observadas diferenças entre ratos desnutridos e controles. Na reversão, o índice de discriminação caiu para valores ao redor de 30% na primeira sessão de reversão, sugerindo persistência do controle pelo estímulo discriminativo da fase anterior no início da reversão. Isso ocorreu igualmente para todos os grupos, embora a taxa de respostas dos ratos desnutridos na condição luz mostre uma reversão mais rápida do que a dos demais grupos. Esses dados apontam a necessidade de aprimoramento nos procedimentos para identificar se ocorrem alterações na aprendizagem de discriminação decorrentes da desnutrição. Palavras-chave: desnutrição proteica, discriminação de estímulos, reversão da discriminação, pressão à barra, ratos