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A recent Cyberball study has indicated that the experience of loss of control can affect how people process subsequent social exclusion. This "preexposure effect" supports the idea of a common cognitive system involved in the processing of different types of social threats. To test the validity of this assumption in the current study, we reversed the sequence of the preexposure setup. We measured the effects of social exclusion on the subsequent processing of loss of control utilizing event-related brain potentials (ERPs) and self-reports. In the control group (CG, n = 26), the transition to loss of control elicited significant increases in both the P3 amplitude and the self-reported negative mood. Replicating the results of the previous preexposure study, these effects were significantly reduced by the preexposure to an independent social threat (here: social exclusion). In contrast to previous findings, these effects were not modulated by the discontinuation (EG1disc, n = 25) or continuation (EG2cont, n = 24) of the preexposure threat. Given that the P3 effect is related to the violation of subjective expectations, these results support the notion that preexposure to a specific social threat has widespread effects on the individuals' expectancy of upcoming social participation and control. [ABSTRACT FROM AUTHOR]

Improved vaccine efficacy has a major impact on future rabies prevention and control. In this systematic review, a comparative assessment of different nucleic acid-based antirabies vaccination tools developed using different methods, in different countries, was undertaken. The comprehensive search was done in three databases. Articles were carefully selected based on predetermined inclusion/exclusion criteria and eight articles were included in this systematic review. Studies have demonstrated dose-dependent immune response following intramuscular vaccination and improved immune response following intranasal vaccination and gene-gun delivery method. Nucleic acid-based antirabies vaccines have shown higher immune response and protective levels in Bagg's albino (BALB/c) mouse models than cell culture-derived vaccines. It has been demonstrated that the route/method of administration and the vaccine formulation could be improved in various ways to enhance immune response following vaccination. These new vaccine tools and their implementation in pre- and postexposure prophylaxis could be further evaluated and to be adopted by rabies endemic countries.

Previous studies indicated that the onsets of different social threats, such as threats to "belonging" and "control", are inconsistent with the subjective beliefs of social participation and require readjustment of expectations. Because a common cognitive system is assumed to be involved, the adjustment triggered by the experience of a single social threat should affect the processing of subsequent social interactions. We examined how preexposure to a loss of control affected social exclusion processing by using the Cyberball paradigm. An event-related brain component (P3) served as a probe for the state of the expectancy system, and self-reports reflected the subjective evaluations of the social threats. In the control group (n = 23), the transition to exclusion elicited a significant P3 effect and a high threat to belonging in the self-reports. Both effects were significantly reduced when the exclusion was preceded by preexposure to a loss of control (EG1disc, n = 23). These effects, however, depend on the offset of the preexposure. In case of a continuation (EG2cont, n = 24), the P3 effect was further reduced, but the threat to belonging was restored. We conclude that the P3 data are consistent with predictions of a common expectancy violation account, whereas self-reports are supposed to be affected by additional processes. [ABSTRACT FROM AUTHOR]

Previous studies indicated that the onsets of different social threats, such as threats to ”belonging” and “control”, are inconsistent with the subjective beliefs of social participation and require readjustment of expectations. Because a common cognitive system is assumed to be involved, the adjustment triggered by the experience of a single social threat should affect the processing of subsequent social interactions. We examined how preexposure to a loss of control affected social exclusion processing by using the Cyberball paradigm. An event-related brain component (P3) served as a probe for the state of the expectancy system, and self-reports reflected the subjective evaluations of the social threats. In the control group (n = 23), the transition to exclusion elicited a significant P3 effect and a high threat to belonging in the self-reports. Both effects were significantly reduced when the exclusion was preceded by preexposure to a loss of control (EG1disc, n = 23). These effects, however, depend on the offset of the preexposure. In case of a continuation (EG2cont, n = 24), the P3 effect was further reduced, but the threat to belonging was restored. We conclude that the P3 data are consistent with predictions of a common expectancy violation account, whereas self-reports are supposed to be affected by additional processes.

An editorial is presented which discusses rabies booster injections, whether administered via the intradermal (ID) or intramuscular (IM) route following ID or IM preexposure prophylaxis (PrEP), elicited neutralizing antibodies. It mentions that World Health Organization (WHO) has updated its recommendation for preexposure prophylaxis (PrEP).

Rationale: Exogenous brain-derived neurotrophic factor (BDNF) in the insular cortex (IC) is known to influence conditioned taste avoidance (CTA) learning, but little is known of its endogenous role in the phenomenon. Preexposure to many abusable compounds attenuates their ability to induce CTA, thus providing a possible platform from which to further elucidate the endogenous role of IC BDNF in CTA. Objectives: The role of IC BDNF in CTA learning was examined by assessing the effect of preexposure to methylphenidate (MPH) on MPH-induced CTA, followed by expression between preexposure groups of BDNF in the IC, central nucleus of the amygdala (CeA), and the nucleus accumbens (NAc). Methods: Following preexposure to MPH (18 mg/kg), CTAs induced by MPH (0, 10, 18, and 32 mg/kg) were assessed in adult male Sprague-Dawley rats ( n = 64). In separate groups ( n = 31), differences in BDNF and tropomyosin-related kinase receptor-B (TrkB) were assessed using Western blots following similar preexposure and conditioning procedures. Results: Preexposure to MPH significantly blunted MPH-CTA compared to preexposure to vehicle. Unexpectedly, there were no significant effects of MPH on BDNF activity following CTA, but animals preexposed to MPH exhibited decreased activity in the CeA and enhanced activity in the IC and NAc. Conclusions: Preexposure to MPH attenuates its aversive effects on subsequent presentations, and BDNF's impact on CTA learning may be dependent upon its temporal relation to other CTA-related intracellular cascades. [ABSTRACT FROM AUTHOR]

Nonhungry rats received training consisting of intermixed presentations of a compound flavor and an element of that compound (AX, X, AX, X, . . .), and then a separate block of presentations of another compound (BX, BX, BX, . . .). Stimuli A and B were two odor solutions (almond and vanilla), and stimulus X was a highly concentrated solution of sucrose. After training, a state of hunger was induced in the rats, and their consumption levels of A and B alone were tested. We found higher test consumption of B than of A (Exp. 1). We interpreted these differences as indicating that the B-X association had become stronger than the A-X association as a result of the training. In Experiment 2, we demonstrated that the presence of X during training was necessary for that effect to appear (Exp. 2). These results give support to the recent proposal that within-compound associations are maintained better by blocked than by intermixed preexposure (Rodríguez & Alonso, ). We discuss the implications of this difference for explaining the intermixed-blocked perceptual-learning effect. [ABSTRACT FROM AUTHOR]

According to a recent theory (Hall & Rodriguez, 2010), the latent inhibition produced by nonreinforced exposure to a target stimulus (B) will be deepened by subsequent exposure of that stimulus in compound with another (AB). This effect of compound exposure is taken to depend on the addition of a novel A to the familiar B and is not predicted for equivalent preexposure on which AB trials precede the A trials. This prediction was tested in 2 experiments using rats. Experiment 1 used an aversive procedure with flavors as the stimuli; Experiment 2 used an appetitive procedure with visual and auditory stimuli. In both, we found that conditioning with B as the conditioned stimulus proceeded more slowly (i.e., latent inhibition was greater) in subjects given the B-AB sequence in preexposure than in subjects given the AB--B sequence. [ABSTRACT FROM AUTHOR]

In Experiment 1, we demonstrated an intermixed-blocked effect where intermixed preexposure to a flavor compound and to an element of that compound (AX, X, AX, X...) reduced generalization between them more than equivalent blocked preexposure (AX, AX... X, X..., or X, X, AX, AX). Then we used sensory preconditioning (Experiment 2) and conditioned flavor preference (Experiment 3) procedures to assess the strength of the X-A within-compound association resulting from those preexposure schedules. In both experiments, we observed that the within-compound association was stronger after blocked than intermixed preexposure. We suggest that these differences in strength produce more mediated generalization in the blocked than intermixed preexposure. [ABSTRACT FROM AUTHOR]

Although preliminary studies showed that preexposure prophylaxis (PrEP) lowers the HIV transmission in individuals with HIV, confirmative trials are ongoing and PrEP is not routinely recommended. The aim of this study was to assess whether individuals with HIV share antiretroviral (ARV) drugs for PrEP and to describe awareness and discussion on PrEP in this population. A cross-sectional survey was conducted in France in 23 representative departments of infectious diseases and internal medicine. Physicians administered an anonymous standardized questionnaire to all individuals with HIV receiving ARVs and followed between 24 and 31 October 2011. The questionnaire included items regarding PrEP (awareness; discussion with their close circle, physician or patients' association; experience), personal sociodemographic characteristics, risk behaviors and HIV status of the participants. Five hundred and ninety three participants were recruited: male 74.2% (men who have sex with men 52.4%, heterosexuals 21.6%), member of patient's association 9.8%. Half of them (50.6%) lived with a stable partner and 35.2% with an HIV-negative partner. Almost half (41.8%) were aware and 29.5% had had discussion about PrEP. In logistic regression, awareness and discussion on PrEP were more frequent: (1) among males, in patients' association members (p< 0.001 for both) and in nonheterosexuals (p=0.023 and 0.057, respectively); (2) among women, in those not living with a stable partner (p=0.035 andp=0.03, respectively) or living with an HIV-negative partner (p=0.049 andp=0.083, respectively). One percent of the participants declared having shared ARVs with someone and 8.3% reported PrEP in their close circle. Men reporting PrEP in their close circle shared ARVs more frequently than those who did not (10.3% vs. 0.2%,p< 0.001). Today, individuals with HIV do not seem to widely share personal ARVs for PrEP with seronegative people. A significant number of individuals with HIV are aware of and commonly discuss PrEP. [ABSTRACT FROM PUBLISHER]

Abstract: The capability to acquire context conditioning does not emerge until weaning, at least when the defining features of the context lack explicit and salient olfactory cues. Contextual learning deficits in preweanling rats have been associated with functional immaturity of the dorsal hippocampus. According to recent studies, the so-called context preexposure facilitation effect (CPFE) – a hippocampus-dependent effect – is not observed until postnatal day 23 (PD23). In these studies the footshock intensity employed was higher (1.5mA) than in adult studies, and context conditioning was inferred from a single behavioral measure (percentage of freezing). The present study examined the CPFE on PD17 and PD23 by analyzing multiple dependent variables, including fecal boli and an ethogram covering the complete behavioral repertoire of the rat. A non-shocked control group was included in the design and two footshock intensities were employed (0.5 and 1.5mA). Results showed clear evidence of contextual fear conditioning in preweanling and weanling rats, as well as evidence of conditioned fear in non-preexposed rats from both age groups. In some cases, some dependent variables, such as grooming or vertical exploration, were more sensitive than freezing for detecting evidence of memory. Strong fear responses were detected in weanling (but not preweanling) rats, when rats were evaluated in a different context from the one employed at conditioning. These results indicate that preweanling rats are capable of acquiring contextual conditioning, even in a context lacking explicit odor cues, and highlight the importance of multiple dependent variables for analyzing the ontogeny of memory. [Copyright &y& Elsevier]

Rationale: The abuse potential of a given drug may be mediated by both its rewarding and aversive effects, the latter of which are often far less characterized. Objectives: Using the conditioned taste-aversion (CTA) preparation, the present experiments examined changes in the aversive effects of the commonly used recreational drug MDMA following repeated drug exposures. Methods: Experiment 1 used three varying doses of MDMA (1.0, 1.8, and 3.2 mg/kg) to determine a dose that produced taste aversions of intermediate strength. Experiments 2 and 3 characterized the effects of repeated preexposures to MDMA (1.8 or 3.2 mg/kg) on taste aversions induced by MDMA (1.8 mg/kg). Additionally, levels of several monoamines and metabolites were analyzed in frontal cortex and caudate-putamen from subjects in Experiment 3 to assess for persistent monoamine depletions. Results: MDMA induced dose-dependent taste aversions. Preexposure to MDMA (at both doses) resulted in an attenuation of MDMA-induced taste aversions. These effects were not likely due to persistent monoamine depletions, as subjects preexposed to the higher MDMA dose did not differ from controls in levels of monoamines or metabolites in either brain region examined. Conclusions: Prior MDMA experience weakened the ability of MDMA to induce taste aversions. This attenuation of MDMA's aversive effects may occur with low doses that do not persistently alter monoamine levels. [ABSTRACT FROM AUTHOR]

Abstract: Smoking continues to be a major health problem and unfortunately smoking cessation interventions have limited success; the conditioning effects of nicotine and individual differences in tobacco addiction are important factors that underlie this setback. The aim of the current study was to investigate nicotine-induced conditioned place preference (CPP) in male and female rats which were previously exposed to a free choice of oral nicotine or water and showed different preferences for nicotine; subsequently nicotine intake also varied between subjects. Exposure patterns were varied in three experiments to allow for assessing the effect of adult v.s. adolescent exposure. The design of CPP testing enabled testing for the possible confounding effects of withdrawal or tolerance. A total of 150 male and female rats were used in three experiments. The oral nicotine choice was provided for at least six weeks in all experiments. Our results replicate our previous findings that nicotine induces CPP in male, but not female rats not pre-exposed to nicotine. Previous nicotine exposure, irrespective of the amount of nicotine consumed, eliminated the conditioning effects of nicotine in a new context. The diminished CPP response was more pronounced in rats exposed to nicotine as adolescents than those exposed as adults. This reduced responsiveness cannot be explained by tolerance. The neuroplastic changes caused by chronic nicotine administration or the strong conditioning to receiving nicotine in the home cage before CPP testing may underlie the weakened responsiveness. These findings support the well known clinical notion that smoking cessation attempts are more successful in a novel environment, not previously connected with smoking. [Copyright &y& Elsevier]

Abstract: The majority of smokers begin their habit during adolescence, which often precedes experimentation with alcohol. Interestingly, very little preclinical work has been done examining how exposure to nicotine during periadolescence impacts the affective properties of alcohol in adulthood. Understanding how periadolescent nicotine exposure influences the aversive effects of alcohol might help to explain why it becomes more acceptable to this preexposed population. Thus, Experiment 1 exposed male Sprague Dawley rats to either saline or nicotine (0.4mg/kg, IP) from postnatal days 34 to 43 (periadolescence) and then examined changes in the aversive effects of alcohol (0, 0.56, 1.0 and 1.8g/kg, IP) in adulthood using the conditioned taste aversion (CTA) design. Changes in blood alcohol concentration (BAC) as well as alcohol-induced hypothermia and locomotor suppression were also assessed. To determine if changes seen were specific to nicotine exposure during periadolescence, the procedures were replicated in adults (Experiment 2). Preexposure to nicotine during periadolescence attenuated the acquisition of the alcohol-induced CTAs (at 1.0g/kg) and the hypothermic effects of alcohol (1.0g/kg). Adult nicotine preexposure produced similar attenuation in alcohol''s aversive (at 1.8g/kg) and hypothermic (1.8g/kg) effects. Neither adolescent nor adult nicotine preexposure altered BACs or alcohol-induced locomotor suppression. These results suggest that nicotine may alter the aversive and physiological effects of alcohol, regardless of the age at which exposure occurs, possibly increasing its overall reinforcing value and making it more likely to be consumed. [Copyright &y& Elsevier]

Abstract: Sugar is often used in learning and conditioning studies as an unconditioned stimulus (US) to enhance liking for a flavor mixed with it. To use sugar as a US, participants are selected only if they like the taste of sugar based on their ratings of a sweetened water US during a preexposure trial prior to experimental procedures. This US-only trail introduces a potential sensory bias and can lead to participant attrition when such a trial is conducted the day prior to experimental procedures. The aim of the present study was to construct a brief scale, called the Estimated Daily Intake Scale for Sugar (EDIS-S), to measure a participant''s exposure to sugar in their diet. It was hypothesized that exposure to sugar would be positively correlated with liking for sugar. As expected, an 11-item EDIS-S was reliable and significantly correlated with ratings of liking for a sweetened taste solution. Implications for the use of the EDIS-S as an assessment in many areas of research, and as a participant selection tool for conditioning studies are discussed. [Copyright &y& Elsevier]

Abstract: Although cocaine-induced conditioned taste aversions (CTA) are well documented, little is known about the basis for cocaine''s aversive effects. To address the role of serotonin (5-HT) in cocaine-induced aversions, the present experiments used the cross-drug preexposure design in which the effects of exposure to fluoxetine, a selective 5-HT reuptake inhibitor (SSRI) with 5-HT transporter (SERT) inhibitory properties, were examined on aversions induced by cocaine (a nonselective monoamine transport inhibitor) and the effects of cocaine preexposure were examined on fluoxetine-induced aversions. Prior to these assessments, a fluoxetine dose–response function (3.2, 5.6, 10, and 18mg/kg) was established in male Sprague–Dawley rats to determine a dose of fluoxetine that would induce intermediate aversions that were comparable to those induced by 18mg/kg cocaine (Experiment 1). Other groups of rats were then exposed to fluoxetine prior to aversion conditioning with cocaine (Experiment 2) and with cocaine prior to aversion conditioning with fluoxetine (Experiment 3). All drugs were administered subcutaneously (cocaine 18mg/kg; fluoxetine 10mg/kg). Although there was no effect of fluoxetine preexposure on either cocaine- or fluoxetine-induced aversions, preexposure to cocaine significantly attenuated aversions induced by itself and by fluoxetine. These results were discussed in terms of the possible role 5-HT might play in the mediation of aversions induced by cocaine. [Copyright &y& Elsevier]

Abstract: Swimming endows rats with an aversion to a taste solution consumed before swimming. The present study explored whether the experience of swimming before or after the taste-swimming trials interferes with swimming-based taste aversion learning. Experiment 1 demonstrated that a single preexposure to 20min of swimming was as effective as four or eight preexposures in causing the interference effect. Experiment 2 found that a single 5-min preexposure was enough to cause the interference effect. Experiment 3 showed that preexposure to swimming interfered with but did not completely thwart the acquisition of swimming-based taste aversion learning. Experiment 4 failed to demonstrate a reliable retroactive interference effect by swimming postexposures. With a modified procedure, however, Experiment 5 successfully demonstrated a reliable effect by four postexposures. The associative and habituation accounts of these results are discussed. [Copyright &y& Elsevier]

Six experiments used a magazine approach paradigm with rats to investigate latent inhibition (LI). Experiment I found that compound conditioning did not increase evidence for LI, in contrast to predictions from acquisition-deficit models that are based on a common error term (e.g., J. M. Pearce & G. Hall, 1980; A. R. Wagner, 1981). Instead, it appeared that preexposed and non-preexposed stimuli conditioned to the same asymptote following compound conditioning, as is the case then these stimuli are conditioned separately. This was confirmed in three further experiments that used probe trials to measure conditioning to each conditioned stimulus across the course of compound training. In these experiments, LI was observed during initial but not extended compound training, consistent with predictions derived from M. E. Bouton (1997) and the SLG model (N. A. Schmajuk, Y. Lam,j& J. A. Gray, 1996). However, 2 further experiments did not support these models. lhstead, these findings are most consistent with models that use separate error terms to compute the associative strength of conditioned stimuli conditioned in compound (S. E. Brandon, E.H. Vogel, & A. R. Wagner, 2003; M. E. Le Pelley, 2004; N. J. Mackintosh, 1975). [ABSTRACT FROM AUTHOR]

Abstract: Despite the impact of cocaine''s aversive effects on its abuse potential, the neurochemical basis of these aversive effects remains poorly understood. By blocking the reuptake of the monoamine neurotransmitters dopamine (DA), norepinephrine (NE) and serotonin (5-HT) into the presynaptic terminal, cocaine acts as a potent indirect agonist of each of these systems. The following studies attempted to assess the extent of monoaminergic mediation of cocaine''s aversive effects using conditioned taste aversion (CTA) learning [ Conditioned aversion to saccharin resulting from exposure to gamma radiation. Science 1955;122:157–158.]. Specifically, Experiment 1 assessed the ability of selective monoamine transporter inhibitors, e.g., DAT (vanoxerine), NET (nisoxetine) and SERT (fluoxetine), to induce taste aversions (relative to cocaine). Only the NET inhibitor approximated the aversive strength of cocaine. Experiment 2 compared the effects of pretreatment of each of these transport inhibitors on the development of a cocaine-induced CTA. Pretreatment with nisoxetine and fluoxetine both attenuated cocaine-induced aversions in a manner comparable to that produced by cocaine itself. The DAT inhibitor was without effect. Combined, the results of these investigations indicate little or no involvement of dopaminergic systems in cocaine''s aversive effects while NE appears to contribute most substantially, with a possible modulatory involvement by serotonin. [Copyright &y& Elsevier]

Abstract: Although cocaine readily induces taste aversions, little is known about the mechanisms underlying this effect. The present series of studies used the cross-drug preexposure design to determine if desipramine (DMI), a selective NE transporter (NET) inhibitor, and cocaine (a nonselective monoamine transport inhibitor) induce aversions by a common mechanism, specifically increases in NE activity. Male Sprague-Dawley rats were exposed to DMI prior to aversion conditioning with cocaine (Experiment 1) and with cocaine prior to aversion conditioning with DMI (Experiment 2). All drugs were administered subcutaneously at 18 mg/kg. Preexposure to DMI attenuated aversions induced by cocaine. However, preexposure to cocaine did not weaken DMI-induced aversions and, in fact, potentiated aversions induced by DMI on several trials. The asymmetrical results are discussed in terms of the possible role NE might play in the mediation of aversions induced by cocaine. Additionally, serial use of these compounds is discussed in terms of clinical implications. [Copyright &y& Elsevier]

In Experiment la, participants were exposed, over a series of trials, to separate presentations of 2 similar checkerboard stimuli, AX and BX (where X represents a common background). In one group, AX and BX were presented on alternating trials (intermixed), in another, they were presented in separate blocks of trials (blocked). The intermixed group performed to a higher standard than the blocked group on a same-different test. A superiority of intermixed over blocked exposure was also evident in a within-subject design (Experiment 1b) and when the test required discrimination between a preexposed stimulus and the background (e.g., AX vs. X), even if the background changed between preexposure and test (AY vs. Y) (Experiment 2). In Experiment 3, the intermixed/blocked effect was observed when, in preexposure, stimulus presentations were alternated with the background alone (e.g., AX/X). This suggests that the perceptual learning effect is not the consequence of inhibitory associations between unique features but to increased salience of those features. Experiment 4 confirmed this finding and also ruled out an account of the effect in terms of trial spacing. [ABSTRACT FROM AUTHOR]

In 2 experiments, rats received preexposure to 2 compound contexts: AB and CD for the congruent group and AC and BD for the incongruent group. Subsequently, all rats received a configural discrimination in which separate placement in contexts A or B indicated that presentations of stimulus X would be followed by food and presentations of Y would not, and separate placement in contexts C and D indicated that Y would be followed by food and X would not. In both experiments, rats in the congruent group acquired the conditional discrimination more rapidly than those in the incongruent group. These results are inconsistent with conventional associative accounts of either stimulus preexposure effects or configural learning and instead provide support for a connectionist account. [ABSTRACT FROM AUTHOR]

Interrelationships between the discriminative stimulus and reinforcing properties of psychoactive drugs and the way in which they may interact to control drug intake are unclear. Studies have shown that drug history can influence the expression of drug-produced behavioral effects. Objective: The present study examined the acquisition and maintenance of intravenous cocaine self-administration in rats with a history of drug discrimination. Methods: Two groups of male hooded rats (n=12 each) were successfully trained in a single-lever food-reinforced procedure to discriminate cocaine (10 mg/kg) from saline. Control groups (n=12 each) received drug injections and/or saline injections only and lever-pressed for food reinforcers with no discrimination training. Subsequently, all subjects were implanted with chronic jugular catheters and allowed to nose-poke for infusions of cocaine (0.2 mg/kg per infusion). Results: Initial rates of responding were similar for all groups. Acquisition of self-administration on a FR-10 schedule of drug delivery was significantly faster for cocaine-exposed rats in comparison to all other groups (P<0.02). There were no differences between groups in the breaking points of cocaine and saline on a progressive ratio schedule of self-administration. Dose-response functions were obtained by two methods and were similar for all groups. Conclusion: These results are consistent with earlier studies demonstrating weakly sensitized primary reinforcing properties of cocaine in preexposed rats. Previous learning to discriminate cocaine impaired this sensitization. [ABSTRACT FROM AUTHOR]

Four experiments are reported that demonstrated that dopamine (DA) transmission is involved in the acquisition of latent inhibition (LI) of a conditioned taste aversion. LI refers to weaker conditioning as a consequence of nonreinforced preexposure (PE) of the future conditioned stimulus. Although it is known to depend on DA transmission during the conditioning phase, it is usually thought that the cognitive processes involved in the establishment of LI (during the PE phase) are DA independent. Either amphetamine (AMPH; 0.5 or 1.0 mg/kg) or haloperidol (HAL; 0.1 mg/kg) were injected before 1 or all of the 3 PE sessions. AMPH blocked the acquisition of LI if it was injected before each or before only the last PE session and HAL potentiated LI. [ABSTRACT FROM AUTHOR]

Recent studies of delay eyeblink conditioning (EBC) in young rats have demonstrated different effects of various conditioned and unconditioned stimulus (CS-US) preexposure conditions on learning at different ages. The present study extends this research to trace EBC. Subjects experienced 1 of 3 preexposure conditions (paired CS-US, unpaired CS-US, or no stimuli) at either 20 or 24 days of age. Four days later, they were conditioned using either trace (Experiment 1) or delay (Experiment 2) EBC parameters. Results were similar at both ages tested. Paired preexposure facilitated acquisition of delay but not trace relative to context preexposure. Unpaired preexposure impaired acquisition of both delay and trace. These behavioral findings provide a foundation for hypotheses about the functional maturation of cerebellar, hippocampal, and entorhinal learning circuits. [ABSTRACT FROM AUTHOR]

Abstract: Nonreinforced preexposure to a conditioned stimulus impairs subsequent conditioning with that stimulus. The goal of these studies was to assess the extent to which acquisition performance could be predicted from preexposure performance using a correlational approach. For both preexposure and autoshaping, four measures of performance were computed, including overall average lever pressing, lever pressing in the initial session, percentage change in lever pressing, and slopes. These measures were correlated in a large sample of rats trained in an autoshaping situation. None of the three measures of autoshaping performance was consistently predicted by any of the three measures of preexposure performance. These results are consistent with the view that latent inhibition is not reducible to long-term habituation. [Copyright &y& Elsevier]

Abstract: This paper reviews recent studies on the influence of trace metal exposure history on subsequent metal uptake in marine invertebrates, particularly bivalves and barnacles. Trace metal exposure may induce specific metal-binding ligands. Metallothionein-like proteins appear to play an important role in mediating metal uptake and hence accumulation, especially for Cd. Other ligands such as sulfide are important for Ag biokinetic changes in bivalves. The incorporation of trace metals into metal-rich granules appears to have little if any effect in modifying trace metal uptake. Furthermore, metals also interact strongly in their accumulation by marine animals. Generally, dissolved Hg uptake is reduced following exposure to other metals such as Ag, Cd, Cu, and Zn. Preexposure of marine mussels to Zn also causes concomitant changes in the uptake of other metals such as Cd sharing similar transport pathways. In general, barnacles are less responsive than mussels to trace metal exposure, presumably because of the dominance of detoxificatory pathways in which the accumulated metals are bound in granules (relatively biologically inactive pools). The tissue body burden and the detoxificatory fate of metals in animals seem to be more important in affecting metal accumulation than the nature of the exposure routes (aqueous vs. dietary) or of the exposure regimes. Trace metal accumulation may also be variable in different natural populations of bivalves as a result of different physicochemical environments and histories of exposure. We finally suggest a few areas for future research in this field. [Copyright &y& Elsevier]

Abstract: Genetic variables are thought to interact with environmental factors, such as alcohol exposure history, to produce individual differences in alcohol abuse and alcoholism. The objective of this study was to test the potential interaction between genetic predisposition to consume alcohol and alcohol pretreatment on subsequent self-administration. To accomplish this goal, four groups of mice from the ethanol-avoiding DBA/2J (D2) and ethanol-preferring C57BL/6J (B6) inbred strains were exposed to saline, acute ethanol (2 g/kg), or chronic intermittent ethanol (1 or 2 g/kg) intraperitoneal (i.p.) injections. Locomotor activity was monitored after each injection. After preexposure, animals were given a two-bottle choice test with various concentrations of ethanol/sucrose vs. sucrose or ethanol vs. water for 4 days at each concentration. Then, all animals were challenged with a 2.0 g/kg ethanol i.p. injection and locomotor activity was assessed. Acute and chronic ethanol pretreatment increased locomotor activity in response to a challenge dose of ethanol (2 g/kg) in D2 mice but had no effect on B6 mice. Prior exposure to ethanol altered the amount of ethanol consumed in a mouse strain-dependent manner. D2 mice showed a positive relationship between ethanol intake and dose or duration of ethanol preexposure. B6 mice preexposed to ethanol consumed more ethanol than naïve animals, independent of dose or duration of exposure. During the last phase of self-administration testing, D2 mice exposed to chronic ethanol (2 g/kg) consumed as much ethanol as B6 from the same pretreatment condition. After a history of ethanol self-administration, saline control mice from the D2 strain showed equal locomotor activation as compared to D2 mice that were pretreated with ethanol injections. B6 mice showed no change in locomotor activity after ethanol self-administration or injection. These results demonstrate that genetic predisposition to avoid alcohol (D2 mice) can be modified by a history of preexposure and that a predisposition to prefer alcohol (B6 mice) may be also amenable to influence by drug history. In general, the results of this study suggest that genetic factors may interact with previous exposure to ethanol to modify ethanol self-administration. [Copyright &y& Elsevier]

The disruption of latent inhibition (i.e. conditioning rate to a preexposed (PE) stimulus elevated to the level of a non-preexposed (NPE) stimulus) within the schizophrenia continuum has often been attributed to increased attentional distractibility by irrelevant stimuli. It has not been established, however, whether such a putative distractibility is due to a tendency to treat any stimulus as salient on the basis of physical characteristics (enhanced stimulus salience). In order to test this possibility, extreme schizotypy scorers were selected from a larger sample of undergraduate students to take part in a two-experimental investigation. In Experiment 1, latent inhibition, as assessed in a visual search paradigm, was disrupted in high-schizotypy scorers, but was intact for low-schizotypy scorers replicating past findings. In Experiment 2, no evidence for an enhanced stimulus salience, as assessed in a visual pop-out task, was found for high-schizotypy scorers. Accuracy rate for both high- and low-schizotypy scorers followed the hierarchically differentiated pattern of the stimulus salience level, failing to support the hypothesis that high-schizotypy scorers tend to treat any stimulus as salient on the basis of physical characteristics. The obtained results suggest that the disruption of latent inhibition in high-schizotypy scorers is not associated with a tendency to experience any event (i.e. both PE and NPE stimuli) as perceptually salient. [Copyright &y& Elsevier]

In rats, stimulus–nicotine associations can be altered by preexposure to the nicotine US (unconditioned stimulus). This alteration differs with the conditioning preparation. In a conditioned taste avoidance preparation, preexposure to nicotine weakens conditioning. In contrast, nicotine preexposure enhances acquisition of a nicotine-conditioned place preference. No one has examined the effects of US preexposure on nicotine locomotor conditioning. In three separate experiments, we assessed the effects of nicotine preexposure on the subsequent expression of conditioned hyperactivity produced by a nicotine US. We found evidence for nicotine-conditioned locomotor sensitization in non-preexposed rats that received repeated pairings of a distinct context with the psychomotor effects of a 0.42 mg/kg dose of nicotine (free base). Conditioning was not observed at lower nicotine doses (0.18 and 0.11 mg/kg) in non-preexposed rats. Preexposure to the 0.42 and 0.18 mg/kg doses of nicotine (3 or 9 days) attenuated acute locomotor suppression and enhanced the development of locomotor sensitization to that same dose. Despite similar qualitative shifts in the locomotor profile induced by preexposure to the nicotine US, conditioned hyperactivity was only altered after 3 or 9 days of preexposure at the 0.18 mg/kg dose. Thus, similar to place conditioning, nicotine preexposure can enhance the subsequent effectiveness of the nicotine US in a locomotor conditioning preparation. [Copyright &y& Elsevier]

Five sets of experiments were carried out with CD1 mice tested in a one-trial inhibitory avoidance task. In a first set, immediately posttraining administrations of the endogenous ligand for the cannabinoid CB1 receptor anandamide (arachidonylethanolamide) (3 or 6 mg/kg) dose-dependently impaired memory consolidation in mice. A lower dose (1.5 mg/kg) was ineffective. In a second set of experiments, which was carried out at the same time of the first set, preexposure of the animals to the testing apparatus decreased the effect of the drug, as compared with non-preexposed mice. In a third set of experiments, administration of anandamide (3 or 6 mg/kg) prior to the retention test did not affect the retention performance of mice given posttraining injections of either saline or anandamide. These findings indicate that the memory-impairing effects of posttraining administration of anandamide are not state-dependent. In the fourth and fifth series of experiments, carried out with non-preexposed mice, an otherwise ineffective immobilization stress (15 min) enhanced the memory-impairing effect of anandamide, and an otherwise ineffective dose of naltrexone (0.1 mg/kg) completely antagonized the effect. The results are discussed in terms of attenuation of emotionality, resulting in impaired retention, following anandamide administration, and of involvement of opioid system in the effect of this drug. [Copyright &y& Elsevier]

Odours are judged to smell sweeter following simultaneous oral pairings with the tastant sucrose and sourer after parings with the tastant citric acid. This effect may result from human participants perceiving and encoding a unitary odour-taste percept. This study examined two factors thought likely to disrupt such encoding; (a) preexposure to the mixture elements and (b) training to spot the elements of taste-odour mixtures. Half of the participants were trained to identify tastes and smells and half received no training. All participants were preexposed to two odours (A, B) and two tastes (X, Y), followed by pairings of these stimuli (AX, BY) and then by pairings between two non-preexposed odours and the same tastes (CX, DY). This process was then repeated on a second session. Odour-taste learning was retarded following preexposure, but was unaffected by training. These findings suggest; (1) that odour-taste mixtures may be cognitively impenetrable and (2) that preexposure leads to encoding of A and B, which are then resistant to interference when further pairings are presented (i.e. AX, BY). [Copyright &y& Elsevier]