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LEARNING TO ASSOCIATE AVERSIVE EVENTS WITH ENVIRONMENTAL STIMULI THAT RELIABLY PREDICT THESE EVENTS IS INDISPENSABLE TO THE SURVIVAL of organisms. Pavlovian fear conditioning is an example of such learning in which an emotionally neutral conditioned stimulus (CS), such as a tone, is paired with an aversive, unconditioned stimulus (US), usually electrical footshock.1 The CS, by virtue of its relationship with the US, acquires aversive properties and elicits responses normally induced by threatening stimuli, such as freezing and ultrasonic vocalizations.2 This paradigm has been used in numerous studies to explore mechanisms that may underlie the psychophysiological alterations associated with posttraumatic stress disorder (PTSD). Experiencing traumatic and aversive events in humans can induce several long-term behavioral and physiological disturbances, including changes in sleep.3,4 Sleep alterations also result from exposure to fear conditioning in both rats5–7 and mice.8,9 One observes changes in vigilance states characterized predominantly by decreased REM sleep (REMS), while NREM sleep (NREMS) remains unaffected.5,6,8 Although the effects of fear conditioning on REMS can be assessed by looking at REMS in toto, various stressors can also alter its microarchitectural pattern (i.e., parcellation of REMS into sequential and single episodes) in rats.10 REMS can be characterized as sequential-REMS (seq-REMS) (comprised of REMS episodes separated by ≤ 3 min intervals, which appear in clusters), and single-REMS (sin-REMS) (with episodes preceded and followed by >3 min intervals).10 This distinction is important because stressors such as low ambient temperature and immobilization have differential effects on sin-REMS and seq-REMS.10,11 For example, rats placed in a cold environment show a reduction in REMS amount. During the recovery period at a normal room temperature, REMS is increased via an increase in the number of seq-REMS bouts. Because temperature is not tightly regulated during REMS due to an absence of hypothalamic control, Amici et al10 suggest that the brief intervals of wakefulness or NREMS punctuating a REMS cluster allow sufficient REMS to be made up by ensuring short periods of homeostatic regulation of the body during a cluster, and that this could not occur, were the REMS deficit to be made up by extended periods of sin-REMS. Similarly, after immobilization stress, the increase in REMS is associated with only a modest increase in sin-REMS, but a considerable increase in seq-REMS, which may result from recovery from sleep deprivation during the immobilization procedure.11 A bimodal distribution of REMS intervals also exists in other species, including humans.10 Altered sleep quality and/or quantity can itself be stressful to an organism and contribute to the emotional and behavioral disturbances symptomatic of psychiatric disorders. We have reported that exposure to fear-inducing tones (the CS), previously paired with brief, mild electrical footshock, alters both REMS and its microarchitecture,5 but the persistence of these effects over time has received less research attention.8 Interestingly, there is often a progressive increase in memory strength over time following an aversive stimulus (measured as a change in the magnitude of the freezing response), without further exposure to the stimulus itself: this has been referred to as an incubation process.12 Therefore, in this study, we evaluated the impact of reexposure to fearful cues on the sleep architecture and REMS microarchitecture of rats, both 24 hr (short-term effect, Day 1) and two weeks (long-term effect, Day 14) after conditioning. In addition, we examined the effects of reexposure to the CS on a more common behavioral index of anxiety, freezing. We and others have reported earlier that military veterans with PTSD have increased phasic muscle activity during REMS13–15; hence, we also evaluated the frequency of myoclonic twitches as a measure of phasic REMS events. Several studies suggest that fear conditioning alters the amount and microarchitecture of REMS, but does not alter the sleep efficiency or NREMS amount.5,6,8,16 Hence, in this study we hypothesized that reexposure to cues associated with footshock should alter REMS microarchitecture, primarily by changing the sin-REMS, seq-REMS, and cluster amount. We also expected that fear conditioning would increase the number of myoclonic twitches during REMS. Finally, we hypothesized that changes in REMS microarchitecture and myoclonic twitches are also due to conditioned anxiety, and as such should correlate with freezing, a well-established indicator of conditioned anxiety.

Fragile X syndrome (FXS) is the most common form of inherited mental retardation (MR). FXS is typically caused by a mutation of the Fmr1 gene (Verkerk et al. 1991, Cell 65, 905-914). To better understand the role of Fmr1 and its gene product fragile X mental-retardation protein (FMRP) in central nervous system function, researchers have turned to the use of animal model systems to generate an Fmr1 knockout (KO) mouse that is deficient in FMRP (Bakker et al. 1994, Cell 78, 23-33). Unfortunately, a number of studies have found no consistent, robust learning and memory impairment in the Fmr1 KO mice. We conducted a study to assess the performance of Fmr1 KO and wildtype (WT) animals in a leverpress escape/avoidance paradigm. Fmr1 KO and WT littermates were studied in four daily 1-h sessions. The Fmr1 KO mice performed fewer avoidance and total responses than WT mice. The KO animals were not simply deficient in avoidance, but a within-factor ANOVA revealed that they did not acquire the leverpress response to any appreciable degree. Observation during the sessions indicated that the Fmr1 KO animals clearly responded to the shock, eliminating an obvious sensory explanation for the deficit. The fact that other studies have found that the KO mice displayed increased exploratory and locomotor activity compared with WT controls argues against a motoric deficit. Future studies will attempt to delineate the nature of the behavioral deficit as well as attempt to rescue the response with glutamatergic or dopaminergic agents.

To examine the influence of conditioned fear stimuli on sleep-wake states, we recorded sleep in Sprague-Dawley rats after exposure to tones previously paired with footshock. After habituation to a recording chamber and the recording procedure, a baseline sleep recording was obtained the next day. One day later, experimental animals were exposed to shock training designed to induce conditioned fear (FC), consisting of five tone-footshock pairings. The 5-s tones (conditioned stimuli; CS) co-terminated with 1-s footshocks (unconditioned stimuli; US). The next day sleep was recorded for 4 h in the recording chamber after presentation of five CSs alone. Sleep efficiency (total sleep time/recording period) and REM sleep (REM) and non-REM (NREM) measures were determined. While sleep efficiency was not significantly changed after CS presentation, the percentage of total sleep time spent in REM (REM percentage) was reduced in the FC animals. The reduction in REM percentage in the FC animals was due to a decrease in the number of REM bouts. In a separate experiment, we repeated the procedures, except the tones and shocks were presented in an explicitly unpaired (UP) fashion. The next day, presentation of the tones increased REM percentage in the UP group. Results are discussed in terms of the decreases in REM as a response to conditioned fear, and the relevance of these findings to the sleep changes seen in post-traumatic stress disorder (PTSD).

Background A prominent sleep disturbance, likely including a disruption of rapid eye movement sleep (REMS) continuity, characterizes posttraumatic stress disorder (PTSD). We set out to develop a fear conditioning paradigm in rats that displays alterations in sleep architecture analogous to those in PTSD. Methods Baseline polysomnographic recordings of rats were performed in a neutral context to which the rats had been habituated for several days. Rats were then shock- or mock-trained in a distinctly different context, and their sleep was studied the following day in that context. A separate group of rats was shock-trained and studied in the neutral context on the following 2 days. Results Rats that slept in the neutral context exhibited a REMS-selective increase in sleep 24 hours after training and increases in REMS and non-REMS 48 hours after training. In contrast, rats that slept in the presence of situational reminders of the training context exhibited a REMS-selective decrease in sleep 24 hours later. Animals that were mock-trained showed no changes in sleep. Conclusions Shock training induced days-long changes in sleep architecture that were disrupted when the animal was exposed to situational reminders of the training context.

One prominent symptom of post-traumatic stress disorder (PTSD) is avoidance of stimuli reminiscent of the traumatic event. We attempted to study this aspect of PTSD in two experiments. Groups of rats received forty 3-s tailshocks, or served as home cage controls (HCC). Twenty-four hours later, all subjects received a 4-h session of leverpress escape/avoidance conditioning. In Experiment 1, shock periods in the absence of a response were 1 s; in Experiment 2 they were 30 s. No group differences were observed in Experiment 1. In Experiment 2, previously shocked animals made more avoidance responses and had a higher percent avoidance during the fourth hour of the session than controls. Further, previously shocked animals had a higher efficiency ratio (the percent of responses that were avoidances). No group differences were observed in leverpresses during the safety period (an index of anxiety) in either study. Results are discussed in terms of the effects of stress on avoidance behavior as a potential model for this important feature of PTSD.

Voluntary oral self-administration of ethanol in rats has been used to model ethanol consumption and abuse in human beings, with contradictory results. The purpose of the current study was to assess the effect of voluntary ethanol consumption on acquisition of a lever press escape/avoidance task in rats. Male Wistar rats were exposed to ethanol in a limited-access procedure, and either 1 day or 10 days after their last ethanol exposure, animals received a 4-h lever press escape/avoidance session. Control animals were not exposed to ethanol at any time. Animals in the 1-day ethanol-deprivation group performed significantly better than did the other two groups with respect to avoidance responding. There were no group differences in number of lever presses during a safety period, a measure of anxiety. Further, we obtained a significant negative correlation between behavioral performance and change in ethanol consumption after the escape/avoidance session, as well as a significant positive correlation between baseline ethanol consumption and avoidance performance. Results are discussed in terms of the potential neural mediators of the improved avoidance effect in animals in the 1-day ethanol-deprivation group.

Recent evidence indicates that the pro-inflammatory cytokines (PICs) can affect learning and memory processes. To examine the effect of the PICs on leverpress escape/avoidance conditioning, we injected male Sprague-Dawley rats with IL-1beta, IL-6 (both 3.0 microg/kg, i.p.), TNFalpha (6.0 microg/kg, i.p.) or vehicle, 24h before a single 4-h session of leverpress escape/avoidance conditioning. The TNFalpha-treated animals made more avoidance responses and fewer escape responses than controls during the last hour of the session. Further, both TNFalpha- and IL-1beta-treated animals had a higher percent avoidance than controls during the 4th hour of the session. None of the cytokines had an effect on the number of leverpresses during safety, a putative measure of anxiety. Results are discussed in terms of the differential central effects of the pro-inflammatory cytokines and the possible relationship to avoidance conditioning.

Recent research has indicated that the pro-inflammatory cytokines, particularly interleukin-1beta (IL-1beta), can affect learning and memory. We injected male Sprague-Dawley rats with IL-1beta (1.0, 3.0, or 6.0 microg/kg, i.p.) or saline vehicle, 24h before a single 4-h session of leverpress escape/avoidance conditioning. No effect of IL-1beta at any dose was observed in the number of escape responses across the 4-h session. However, subjects treated with the two lower doses (1.0 and 3.0 microg/kg) of IL-1beta performed more avoidance responses during the final hour of the 4-h session than the other two groups. Subjects treated with the highest dose of IL-1beta (6.0 microg/kg) did not differ from controls. Results are discussed in terms of the possible mechanisms behind the IL-1beta-induced enhancement of learning, as well as the observed dose-response relationship.

Whether an organism can control a stressful event is often an important variable determining the impact of the event on physiology and behavior. Numerous behavioral and physiological variables are more adversely affected by uncontrollable stress. The present experiment with rat subjects compared the effect of controllable stress (escape conditioning) or uncontrollable stress (yoked control group) vs. home cage controls on total cholesterol, as well as high-density lipoprotein (HDL) and low/very-low density lipoprotein (LDL/VLDL) serum cholesterol. Results indicated that both stressed groups had higher total and LDL/VLDL cholesterol levels than home cage controls. No group differences were observed with HDL cholesterol. The escape and yoked control subjects did not differ from each other in any dependent measure. Results are discussed in terms of the probable mediators of stress-induced cholesterol increases, and the fact that these mediators may be insensitive to stressor controllability.

In this study we assessed habituation and sensitization of the acoustic startle response (ASR) to discern whether intense, inescapable stress affects nonassociative learning differently in male and female rats. Rats were inescapably stressed 2 hours per day over 3 consecutive days. ASR magnitudes were measured at several times post-stress (1, 4, 8, and 15 days after cessation). Females generally showed greater ASR magnitudes (compared to males), but both sexes exhibited short and long-term habituation across the testing days. ASR magnitudes were only affected by stress in male subjects. The effect in males was an increase in short-term sensitization of the ASR on post-stress day-4. The results suggest that stressed males and females react differently to ASR testing, in that stress males appear to develop an exaggerated ASR response over repeated test sessions due to short-term sensitization. The source of the short-term sensitization is discussed with regards to possible stress-induced enhanced contextual learning during ASR testing on post-stress day-1.

Pharmacogenetic testing as a means of guiding treatment decisions is beginning to see wider clinical use in psychiatry. The utility of this genetic information as it pertains to clinical decision making, treatment effectiveness, cost savings, and patient perception has not been fully characterized.In this retrospective study, we examined health claims data in order to assess medication adherence rates and healthcare costs for psychiatric patients.Individuals for whom pharmacogenetic testing was ordered (cases) were contrasted with those who did not undergo such testing (controls). Cases and controls were propensity score matched in order to minimize risk of confounding in this nonrandomized study. An initial analysis of 111 cases and 222 controls examined both adherence and healthcare costs. A replication study of 116 cases and 232 controls examined adherence alone, as cost data was not available for this latter cohort.Overall, individuals with assay-guided treatment were significantly more medication adherent (P = 1.56 3 10–3; Cohen’s d = 0.511) than patients with standard treatment and demonstrated a relative cost savings of 9.5% in outpatient costs over a 4-month follow-up period, or $562 in total savings.The data show the utility of pharmacogenetic testing in everyday psychiatric clinical practice, as it can lead to improved patient adherence and decreased healthcare costs.

To examine the effectiveness of genetic testing in a real-world setting and to assess its impact on clinician treatment decisions.This was a naturalistic, unblinded, prospective analysis of psychiatric patients and clinicians who utilized a commercially available genetic test (between April and October of 2013), which incorporates 10 genes related to pharmacokinetics and pharmacodynamics of psychiatric medications. Each patient's genetic results were provided to participating clinicians, who completed a baseline survey including patient medications, history, and severity of illness. Clinicians were prompted to complete surveys within 1 week of receiving the genetic results and again 3 months later. Patients likewise completed assessments of depression, anxiety, medication side effects, and quality of life at baseline, 1 month, and 3 months.Data from 685 patients were collected. Approximately 70% and 29% of patients had primary diagnoses of either a mood or anxiety disorder, respectively. Clinician-reported data, as measured by the Clinical Global Impressions-Improvement scale, indicated that 87% of patients showed clinically measurable improvement (rated as very much improved, much improved, or minimally improved), with 62% demonstrating clinically significant improvement. When analysis was restricted to the 69% of individuals with ≥ 2 prior treatment failures, 91% showed clinically measurable improvement. Patients also reported significant decreases in depression (P.001), anxiety (P.001), and medication side effects (P.001) and increases in quality of life (P.001).These results suggest that a substantial proportion of individuals receiving pharmacogenetic testing showed clinically significant improvements on multiple measures of symptoms, adverse effects, and quality of life over 3 months. In the absence of a treatment-as-usual comparator, the proportion of improvement attributable to the test cannot be estimated.ClinicalTrials.gov identifier: NCT01507155.

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Over the last decade, pharmacogenetics has become increasingly significant to clinical practice. Psychiatric patients, in particular, may benefit from pharmacogenetic testing as many of the psychotropic medications prescribed in practice lead to varied response rates and a wide range of side effects. The use of pharmacogenetic testing can help tailor psychotropic treatment and inform personalized treatment plans with the highest likelihood of success. Recently, many studies have been published demonstrating improved patient outcomes and decreased healthcare costs for psychiatric patients who utilize genetic testing. This review will describe evidence supporting the clinical utility of genetic testing in psychiatry, present several case studies to demonstrate use in everyday practice, and explore current patient and clinician opinions of genetic testing.

Exposure to inescapable stress facilitates acquisition of the classically conditioned eyeblink response in freely moving rats. Here, we determined whether facilitated acquisition of the eyeblink conditioned response (CR) depended on the interstimulus interval (ISI). Rats were either stressed (40 2-mA tailshocks delivered over a single 1-h session) or served as nonstressed controls. Paired training was accomplished with a 300-, 500-, 700-, or 1200-ms ISI. Separate groups of stressed and nonstressed rats were exposed to explicitly unpaired stimuli. Consistent with eyeblink conditioning using humans or rabbits as subjects, acquisition depended on the ISI; a “U-shaped” curve was described for nonstressed rats. Acquisition was fastest at the 700-ms ISI; the order was 700 > 500 > 300 > 1200 ms. The unconditioned response decreased with training. Except for the 700-ms ISI, exposure to stress facilitated acquisition. Exposure to stress did not affect the amplitude of the unconditioned response. Facilitated acquisition of the eyeblink CR after exposure to inescapable stressors is independent of nonassociative changes in reactivity to the conditioned stimulus or unconditioned stimulus.

Elevated basal plasma corticosterone concentrations have been observed for several days after the cessation of severe stress. In the present study, we examined whether or not the acute plasma corticosterone response to stress is necessary to elicit increased basal plasma corticosterone concentrations the following day. Pretreatment with metyrapone (100 mg/kg, intraperitoneal) 1 h before inescapable stress (40 2mA tailshocks delivered over a 1-h period) (IS) blocked the acute plasma corticosterone response to IS. However, elevated basal plasma corticosterone concentrations still emerged the next day. These results suggest that the corticosterone response to stress, and its attendant feedback, are not necessary to produce persistent hypothalamic-pituitary-adrenal axis (HPAA) activation.

Exposure of rats to inescapable stressors (IS) results in persistent elevations in plasma corticosterone (CORT), which are selective to the trough of the circadian rhythm. Although affective disorders (depression, anxiety) in humans are also characterized by persistent hypothalamic-pituitary-adrenal axis (HPAA) activation, the predominant measure of HPAA activation in clinical studies is 24-h urinary cortisol. To facilitate interspecies comparisons regarding the persistent effects of stress on HPAA activity, we compared the effects of IS on plasma and urinary CORT in rats. Male Sprague-Dawley rats were exposed to three 2-h sessions of IS (40, 2.0 mA tailshocks) or remained in their home cages. The 24-h urine samples were collected daily from 2 days prior to stress to 5 days after stressor cessation, then weekly for 3 weeks. In addition, plasma samples were obtained at 08:00 (trough) and 20:00 hours (peak) for the first 3 days after stressor cessation and weekly for 3 weeks thereafter. Consistent with our earlier work, plasma CORT elevations were apparent in the trough, but not the peak samples for 3 days after stressor cessation. The 24-h urinary CORT levels were elevated during stressor exposure, and remained elevated for 3 days after stressor cessation. Persistent stress-induced urinary CORT elevations in rats are reminiscent of the clinical HPAA abnormalities described for major depression and affective disorders.

Data were collected on 10 newswriters in a newspaper's newsroom. These included self-reported stress ratings and saliva samples for secretary immunoglobulin A (IgA) analysis. The stress ratings and saliva samples were taken initially and after three 30-min. periods. The first time period was a baseline measure and involved the workers engaging in their usual tasks. At Time 2 music was presented for 30 min. while workers engaged in their normal activities. At Time 3 workers resumed their normal duties. Findings showed an increase in IgA that was not statistically significant, a reduction in stress during the music period that was statistically significant, and a statistically significant negative correlation between stress and IgA.

Many researchers have studied acute responses to stress in animals and how they are modified by prior stressor exposure, but relatively few have examined whether responses to stressors might last for prolonged periods of time. We have previously demonstrated that trough plasma corticosterone levels in rats are elevated for three to five days after single or repeated exposures to mild restraint and inescapable tailshock. The current study measured other aspects of the adrenal axis, and activity in other neuroendocrine systems, 24 hours after one or three consecutive exposures to the same stress paradigm. The data indicated persistent activation of the adrenal axis and prolactin levels, whereas the thyroid and reproductive hormone axes were inhibited after either one or three stress sessions. These changes are remarkable in that one would have expected acute responses to even intense stressors to have ended within hours after the end of the stressor. It will be important to understand the interactions among these responding neuroendocrine systems and to know how long such persistent changes last. Finally, it will be critical to understand the relative contributions of neuroendocrine and psychological factors in maintaining these persistent neuroendocrine changes after exposure to intense stressors.

This study investigated the effects of music and an auditory stimulus on immunoglobulin A (IgA). Groups of college students ( N = 66) were exposed to one of four conditions: a 30-min. tone/click presentation; 30 min. of silence; 30 min. of a Muzak tape referred to as “Environmental Music”; and a 30-min. radio broadcast comparable in musical style. Saliva samples collected before and after each 30-min. treatment were assayed for IgA. Analysis indicated significant increases in IgA for the Muzak condition ( n = 20) but not for any of the other conditions. Possible mechanisms of action and implications for immunocompetence are discussed.

Taste quality and palatability are two of the most important properties measured in the evaluation of taste stimuli. Human panels can report both aspects, but are of limited experimental flexibility and throughput capacity. Relatively efficient animal models for taste evaluation have been developed, but each of them is designed to measure either taste quality or palatability as independent experimental endpoints. We present here a new apparatus and method for high throughput quantification of both taste quality and palatability using rats in an operant taste discrimination paradigm. Cohorts of four rats were trained in a modified operant chamber to sample taste stimuli by licking solutions from a 96-well plate that moved in a randomized pattern beneath the chamber floor. As a rat's tongue entered the well it disrupted a laser beam projecting across the top of the 96-well plate, consequently producing two retractable levers that operated a pellet dispenser. The taste of sucrose was associated with food reinforcement by presses on a sucrose-designated lever, whereas the taste of water and other basic tastes were associated with the alternative lever. Each disruption of the laser was counted as a lick. Using this procedure, rats were trained to discriminate 100 mM sucrose from water, quinine, citric acid, and NaCl with 90-100% accuracy. Palatability was determined by the number of licks per trial and, due to intermediate rates of licking for water, was quantifiable along the entire spectrum of appetitiveness to aversiveness. All 96 samples were evaluated within 90 minute test sessions with no evidence of desensitization or fatigue. The technology is capable of generating multiple concentration-response functions within a single session, is suitable for in vivo primary screening of tastant libraries, and potentially can be used to evaluate stimuli for any taste system.

Three experiments were conducted examining the contribution of beta-adrenergic receptors to stress-induced cholesterol increases. Rats were exposed to 3 90-min sessions of inescapable tailshock, or left undisturbed in their home cage. Propranolol, a nonselective beta-blocker, attenuated the stress-induced cholesterol increase when administered prior to the daily shock session. Atenolol, a beta-1 specific antagonist, also attenuated the stress-induced cholesterol increase. Butoxamine, a beta-2 specific antagonist, had no effect on the stress-induced cholesterol increases. Results are discussed in terms of catecholamine-stimulated free fatty acid (FFA) release as a potential mechanism for producing stress-induced hypercholesterolemia.

The relationship between performance in an avoidance conditioning paradigm and the plasma glucose levels of Sprague-Dawley rats was examined in two experiments. In Experiment 1 we investigated whether glucose levels varied with the animal's relative success at acquiring the avoidance task. Results indicated that animals classified as avoiders (60% avoidance and above) had lower glucose levels than animals classified as escapers (30% avoidance and below). In Experiment 2 we looked at whether glucose levels showed within-subject changes with avoidance acquisition. Results demonstrated that glucose levels showed reductions if an animal learned the avoidance response. Subjects that did not learn the response showed no such reduction. Such results suggest that the physiological response to stress is attenuated by acquisition of successful coping behaviors that exercise control over the onset of aversive events.

Male Sprague-Dawley rats were maintained for three weeks on one of three different diets. Two of the diets were high-cholesterol, high-fat, while the third was standard laboratory chow. Animals from each group were then given either daily 2 hr sessions of tailshock for three days, or left in their home cage. Blood samples were taken from all subjects prior to stress, and again immediately after the third stress session. Sera were separated and analyzed for total plasma cholesterol. Results indicate that total plasma cholesterol was increased in the stressed animals maintained on standard lab chow. Stressed animals in the two high cholesterol diet groups showed no cholesterol increase relative to their respective dietary controls.

We have previously reported that prior exposure to inescapable tailshock stress increased avoidance responding 24 hours later. We argued previously that this might model the avoidance behavior characteristic of post-traumatic stress disorder (PTSD). The current experiment was conducted to determine whether a more ethologically relevant stressor would produce similar effects on avoidance responding. Therefore, rats were restrained for 2 hours and exposed to trimethylthiazoline (TMT), a component of fox feces, restrained only, or served as home cage controls. Twenty-four hours later, subjects received a 4-hour escape–avoidance session. Animals exposed to TMT made more escape responses overall, and made more avoidance responses than the other two groups by the 4th hour of the session. Differences between the TMT-exposed animals and restraint alone could not be explained by differences in corticosterone (CORT) levels. Results are discussed in terms of the possible neural changes induced by TMT exposure and the relationship to the behavioral aspects of PTSD or acute stress.

Many orally administered pharmaceuticals are regarded by humans as aversive, most often described as 'bitter'. Taste aversiveness often leads to patient noncompliance and reduced treatment effectiveness. 'Bitter' taste is mediated by T2R G-protein coupled receptors through a peripheral signaling pathway critically dependent upon function of the TRPM5 ion channel. The brief-access taste aversion (BATA) assay operationally defines aversive taste as suppression of the rate at which a rodent licks from sipper tubes that deliver tastant solutions or suspensions. We have used a mouse BATA assay for rapid quantification of oral aversiveness from a set of 20 active pharmaceutical ingredients (APIs). Robust lick-rate dose-response functions were obtained from both C57BL/6J wild type (WT) and C57BL/6J/TRPM5-/- (TRPM5 knockout) mouse strains, generating reliable determinations of potency and relative maximal oral aversiveness for each API. A subset of APIs was also evaluated in a human bitterness assessment test; effective concentrations for half-maximum responses (EC50s) from both the human test and WT mouse BATA were equivalent. Relative to WT potencies, EC50s from TRPM5 knockout mice were right-shifted more than 10-fold for most APIs. However, APIs were identified for which EC50s were essentially identical in both mouse strains, indicating a TRPM5-independent alternative aversive pathway. Our results suggest the BATA assay will facilitate formulation strategies and taste assessment of late development-phase APIs.

Psychological stressors have a prominent effect on sleep in general, and rapid eye movement (REM) sleep in particular. Disruptions in sleep are a prominent feature, and potentially even the hallmark, of posttraumatic stress disorder (PTSD) (Ross, R.J., Ball, W.A., Sullivan, K., Caroff, S., 1989. Sleep disturbance as the hallmark of posttraumatic stress disorder. American Journal of Psychiatry 146, 697-707). Animal models are critical in understanding both the causes and potential treatments of psychiatric disorders. The current review describes a number of studies that have focused on the impact of stress on sleep in rodent models. The studies are also in Table 1, summarizing the effects of stress in 4-h blocks in both the light and dark phases. Although mild stress procedures have sometimes produced increases in REM sleep, more intense stressors appear to model the human condition by leading to disruptions in sleep, particularly REM sleep. We also discuss work conducted by our group and others looking at conditioning as a factor in the temporal extension of stress-related sleep disruptions. Finally, we attempt to describe the probable neural mechanisms of the sleep disruptions. A complete understanding of the neural correlates of stress-induced sleep alterations may lead to novel treatments for a variety of debilitating sleep disorders.

In addition to their well-known role in neural development, the neurotrophins BDNF and NGF help mediate the plasticity that occurs in the brain to promote learning. Exposure to learning procedures often leads to increases in neurotrophins, while exposure to stress often results in decreases. It is unclear how the neurotrophins would respond to an aversive learning task. Therefore, BDNF and NGF content in the dorsal striatum, hippocampus, and basal forebrain was measured following discrete trial lever-press escape/avoidance conditioning. Conditioning significantly increased levels of both neurotrophins in hippocampus and basal forebrain, relative to home cage controls (HCC). Contrary to expectations, the dorsal striatum did not show any significant changes. However, significant correlations were observed between dorsal striatal neurotrophins and aspects of avoidance performance. This may indicate that the dorsal striatum is involved in the performance aspects of the task. Results are discussed in terms of the role of neurotrophins in the acquisition of new information, and the neural structures involved in different types of memory.

Psychological stressors have a prominent effect on rapid eye movement sleep (REMS) in humans and animals. We hypothesized that the stress-related neurochemical corticotropin-releasing factor (CRF), acting in the amygdala, could initiate neural events that lead to REMS alterations. Therefore, we made bilateral microinjections of three different doses of CRF into the central nucleus of the amygdala (CeA) in five rats. Only the lowest dose of CRF (1 ng) induced a change in sleep, specifically REMS, during the 4-h post-injection period. Thus, REMS alterations following psychological stress may depend, in part, on CRF release in the CeA.

To examine the influence of conditioned fear stimuli on sleep-wake states, we recorded sleep in Sprague-Dawley rats after exposure to tones previously paired with footshock. After habituation to a recording chamber and the recording procedure, a baseline sleep recording was obtained the next day. One day later, experimental animals were exposed to shock training designed to induce conditioned fear (FC), consisting of five tone-footshock pairings. The 5-s tones (conditioned stimuli; CS) co-terminated with 1-s footshocks (unconditioned stimuli; US). The next day sleep was recorded for 4 h in the recording chamber after presentation of five CSs alone. Sleep efficiency (total sleep time/recording period) and REM sleep (REM) and non-REM (NREM) measures were determined. While sleep efficiency was not significantly changed after CS presentation, the percentage of total sleep time spent in REM (REM percentage) was reduced in the FC animals. The reduction in REM percentage in the FC animals was due to a decrease in the number of REM bouts. In a separate experiment, we repeated the procedures, except the tones and shocks were presented in an explicitly unpaired (UP) fashion. The next day, presentation of the tones increased REM percentage in the UP group. Results are discussed in terms of the decreases in REM as a response to conditioned fear, and the relevance of these findings to the sleep changes seen in post-traumatic stress disorder (PTSD).

The present study assessed the effect of petting a dog on secretory immunoglobulin A (IgA) levels. 55 college students were randomly assigned to either an experimental group or one of two control groups. Group 1 ( n = 19) petted a live dog; Group 2 ( n = 17) petted a stuffed dog, while Group 3 ( n = 19) simply sat comfortably on a couch. Each participant was exposed to one of the three conditions for 18 min. Pre- and posttreatment saliva samples yielded a significant increase in IgA for Group 1 only. Participants were also asked to complete the Pet Attitude Scale of Templer, Salter, Dickey, Baldwin and Veleber. Scores on this scale correlated with IgA increases only for participants in Group 2 (petting a stuffed animal). Results are discussed in terms of the beneficial effects of pets on health in general, and immunity in particular.

112 college students reported the frequency of their sexual encounters and were divided into four categories: none, infrequent (less than once a week), frequent (one to two times per week), and very frequent (three or more times per week). Participants also described their overall sexual satisfaction. Saliva samples were collected and assayed for salivary immunoglobulin A (IgA). Individuals in the frequent group showed significantly higher levels of IgA than the other three groups, which were comparable. Data on length of relationship and sexual satisfaction were not related to the group differences.

Studies of inbred mouse strains can provide us with important information about the genetic basis of learning and memory. The present experiment studies the acquisition of a leverpress escape/avoidance task in six commonly studied inbred mouse strains (C57BL/6NCrlBR, DBA/2NCrlBR, C3H/HeJ, FVB/NJ, BALB/cByJ and 129S6/SvEvTac), and one outbred strain, the CD1. Results indicated that the strains formed three discrete performance clusters. The C57BL/6NCrlBR, C3HeB/FeJ, BALB/cByJ, and CD1 strains acquired the avoidance response comparably to Sprague-Dawley rats, avoiding approximately 40% of shocks by the fourth and final training session. The 129S6/SvEvTac and FVB/NJ were extremely poor at the avoidance task throughout training. The FVB/NJ strain remained in an escape mode, while the 129S6/SvEvTac animals performed few responses of any type. Finally, the DBA/2NCrlBR strain performed exceptionally well, avoiding over 90% of the shocks by the final session. Results are discussed in terms of genetic differences in learning and how the nigrostriatal dopamine system may mediate the observed differences.

Leverpress escape/avoidance is an excellent model for assessing coping in rats. Acquisition of the leverpress response is determined by the interstimulus (signal-shock) interval, as well as the type and duration of the aversive event. One factor that has received less research attention is the safety or feedback signal. The safety signal presumably negatively reinforces leverpress responding through fear reduction. Here, we present a parametric manipulation of safety signal length and avoidance performance. All rats were trained with a 60-s tone conditioned stimulus and an intermittent 1-s, 1.0-mA footshock. Training was further accomplished with a 1-, 2-, 4-, or 6-min safety signal. Acquisition of the avoidance response was comparable at all safety signal durations. Rats trained with the shortest safety signal (1 min) exhibited more leverpresses during the safe period, a measure of anxiety. Thus, acquisition of the leverpress avoidance response was efficient regardless of safety signal duration, even though shorter periods were associated with greater anxiety.

Pyridostigmine bromide (PB), a peripheral cholinesterase inhibitor, has been shown to have central cholinesterase inhibition properties under certain conditions (such as when ingested with other chemical compounds or following a high level of stress). Here we tested if stressing rats, using an intermittent 1 hr tailshock protocol, affected the degree of brain acetylcholinesterase (AChE) inhibition caused by a subsequent single injection of PB (2.0 mg/kg) or neostigmine bromide (NB, 0.32 mg/kg), another peripheral carbamate cholinesterase inhibitor. Stressed rats treated with PB had lower levels of AChE activity in the basal forebrain/striatum, but not in other brain areas. Stressed rats treated with NB did not show basal forebrain/striatum AChE activity changes but did show minor reductions of AChE activity in the cortex and cerebellum. These results confirm that prior stress can change the characteristic actions of certain peripherally acting drugs, thus possibly leading to unexpected central nervous system effects. Possible causes for these effects are discussed.

The construct of explanatory style has been related to numerous aspects of human psychology, including health. Our research has focused on the effects of various psychological variables on the immune system, in particular Immunoglobulin A (IgA). We had participants fill out the Attributional Style Questionnaire (ASQ), the predominant measure of explanatory style, and assayed saliva samples for secretory IgA. No relationship was observed between overall ASQ score and IgA, or composite optimism score and IgA. However, we observed significant negative correlations between both the composite pessimism score and IgA, as well as the hopelessness score and IgA. Pessimistic explanatory style may therefore be related to immune system deficits and poor health.

The present experiments examined the sensitivity of the elevated plus-maze to the effects of Stressor controllability. Previous work had established that inescapable but not an equal amount of escapable electric tail shock reduced social interaction. The present experiments demonstrate that prior exposure to shock alters elevated plus-maze behavior, but that this effect is not sensitive to the escapability of the shock. These experiments include a replication of the usual pharmacologic effects of benzodiazepine ligands (2 mg/kg diazepam; 0.4 mg/kg methyl 6,7-dimethoxy-4-ethyl-β-carboline-3-carboxylate) to demonstrate the sensitivity of the elevated plus-maze procedures used. The results provide additional support for the idea that the social interaction and elevated plus-maze measures of “anxiety” are sensitive to different processes.

Exposure to stressors can affect various aspects of immune function, including the antibody response. We have previously reported that rats exposed to an acute session of inescapable tail shock (IS) show long-term reductions in anti-keyhole limpet hemocyanin (KLH) immunoglobulin (Ig) M and IgG and a failure to expand Th1-like cells in response to KLH. To further investigate the potential role of decreased Th1-like cells in the IS-induced reduction of anti-KLH Ig, we examined two isotypes of IgG, IgG1 and IgG2a. Isotype switching is under cytokine control. Interleukin-4 helps B cells switch from making IgM to making IgG1, whereas interferon (IFN)-gamma helps B cells switch from making IgM to making IgG2a. In this paper we report that IS exposure reduces IFN-gamma levels 4 days after exposure to IS+KLH compared with immunized home cage controls. In addition, IS exposure reduced the Th1 cytokine-sensitive anti-KLH IgG2a but not Th2 cytokine-sensitive anti-KLH IgG1. This pattern of isotype reduction suggests that a failure to expand the Th1 cell, which results in less IFN-gamma, may contribute to the the IS-induced reduction in anti-KLH Ig. Glucocorticoids (GCs) differentially regulate Th1 and Th2 cells. Administration of the type II GC receptor antagonist RU-486 before IS blocked the IS-induced suppression in anti-KLH IgM, IgG, and IgG2a. Corticosterone (2.5 mg/kg), however, did not produce the suppression in anti-KLH Ig. These results support a role of corticosterone in mediating IS-induced reductions in in vivo antibody.