Gender differences in acute and chronic stress in Wistar Kyoto (WKY) rats

While females are considered more susceptible to depressive behavior, this assertion is not strongly supported by the experimental literature. Since stress contributes to depressive behavior, male and female Wistar Kyoto (WKY) rats were exposed to either one session (acute stress) or 5 sessions (chronic stress) of restraint plus cold in order to study depressive behavior in male and female rats. After their respective treatment exposure, rats were tested in the open field test (OFT) and for retention of a passive-avoidance (P-A) task. One stress session resulted in significant immobility in the OFT for males, whereas 5 sessions were required to produce similar immobility in female rats. Acute stress interfered with the retention of the P-A response for males, while both acute and chronic stress produced poor P-A responses in female rats. Food consumption decresed, progressively, as a function of stress sessions, in female rats, whereas feeding in males returned to control levels after five stress days. Both acute and chronic stress exacerbated the stress ulcer response in male rats, but not in female rats. Chronic, but not acute, stress resulted in an increase in serotonin transporter mRNA levels in the dorsal raphe nucleus of both male and, female rats. The general consensus from these data suggested that female rats were more vulnerable to chronic stress and consequently supported the notion that females may be more susceptible to stress induced behavioral depression.     

Gastric secretion as a function of acute and chronic stress in the gastric fistula rat.

In Experiment 1 rats exposed to signaled and unsignaled grid shock secreted more gastric acid after shock stress (chronic stress) for 8 days compared to the first 12 hr. of shock stress (acute stress). However, Experiment 2 indicated that the higher gastric acid values under chronic stress were not significantly greater than prestress baseline values. The results are interpreted to reflect an inhibition of gastric acid secretion as a function of acute stress. During chronic stress this inhibition is followed by a habituation of gastric secretory processes which is observed as a return of secretion volume to baseline levels.     

A method for determining the aversive threshold in the rat using repeated measures: Tests with morphine sulfate

The procedure described here provides an objective automated technique for the psychophysical assessment of the aversive threshold and allows the animal Ss to serve as their own controls. Sensitivity to drug effects, as well as comparisons between drugs, using the same animals are possible also. Using a rectangular tilt cage, the aversive threshold to grid shock was defined as that intensity avoided 75% of the time. Each shock intensity (30, 60, 90, 120, and 150 microA) was presented for 5 min on one side of the cage and then switched to the other side for 5 min, thereby forcing the animal to sample each shock intensity. Aversive thresholds were determined daily for each rat. The analgesic effects of morphine sulfate were compared to saline. Animals were tested for 3 days at each morphine dose level (2, 4, 8, and 16 mg/kg). Each 3-day morphine series alternated with 3 days of testing under saline. Significant differences were detected between saline and morphine at 4, 8, and 16 mg/kg.     

Gastric secretion and activity-stress lesions in the rat

In Experiment 1, gastric samples were obtained by means of a pylorus ligation procedure on either the first or last day of the activity-stress procedure. Experimental rats had more stomach lesions and showed a drop in gastric acid on the last day collection. In Experiment 2, rats were surgically prepared with gastric cannulas and pyloric cuffs, and first and last day collections were obtained from the same animal. Experimental activity rats revealed more stomach lesions and a corresponding drop in gastric acid on the last collection than did control rats, which thereby suggests that acid was not a significant etiological variable. The destruction of acid-bearing parietal cells or the back diffusion of hydrogen ions could also explain the low acid values in rats with stomach lesions.     

Validation of distinct amnesic and executive type memory deficit in a psychiatric sample based on retrieval performance

Studies of localized brain dysfunctions have revealed connections between patterns of cognitive dysfunction and specific profiles of memory impairment. The amnesic type of memory impairment is defined by deficits in both free recall and recognition memory, whereas the dysexecutive memory impairment is characterized by retrieval deficits, i.e. a disproportional impairment in free recall relative to recognition memory. The present study tests whether classifications of psychiatric patients into recall impaired only (= RO group) and Recall and Recognition impaired (= RR group) correspond to the executive type and amnesic type of memory impairment. The alternative hypothesis is that the two groups merely differ in degree of neuropsychological and psychiatric disturbance. Forty-four subjects impaired on California Verbal Learning Test (CVLT) were selected from a larger database of 103 impaired and non-impaired subjects with schizophrenia or recurrent major depression. Subjects were classified into RO and RR groups and compared on measures of memory strategy (recency effect and interference on CVLT), overall neuropsychological function (Stroop Test and WAIS-R similarity) and psychiatric symptom load (positive and negative symptoms). Repeated measures ANOVA showed no effects of group, i.e. the RR group did not perform consistently below the RO group with regard to memory strategy, neuropsychological function or psychiatric symptom load. Two out of three analyses showed group x test interaction, supporting the dissociation of distinct executive and amnesic profiles among psychiatric patients. The RO group was more susceptible to interference but had better recency score than the RR group. The RO had higher negative symptoms while the RR group had higher positive symptoms.     

Modulation of anxiety circuits by serotonergic systems

Anxiety is a complex emotional state associated with sustained heightened autonomic and behavioral arousal and an increase in avoidance behavior. Anxiety-related behavior is a form of risk assessment behavior that is associated with a level of uncertainty or unpredictability regarding the outcome of emotionally salient events, often when both rewarding and aversive outcomes are possible. In this review, we highlight recent advances in our understanding of the neural circuits regulating anxiety states and anxiety-related behavior with an emphasis on the role of brainstem serotonergic systems in modulating anxiety-related circuits. In particular, we explore the possibility that the regulation of anxiety states and anxiety-related behavior by serotonergic systems is dependent on a specific, topographically organized mesolimbocortical serotonergic system that originates in the mid-rostrocaudal and caudal parts of the dorsal raphe nucleus.     

Visual search with biological threat stimuli: accuracy, reaction times, and heart rate changes

Twenty-four participants were given a visual search task of deciding whether all the pictures in 3 x 3 search arrays contained a target picture from a deviant category, and heart rate was measured. The categories were snakes, spiders, flowers, and mushrooms. Shorter reaction times (RTs) were observed for fear-relevant (snake and spider) targets rather than for fear-irrelevant/neutral (flower and mushroom) targets. This difference was most pronounced for the participants presented with a gray-scale version of the search arrays. The 1st interbeat interval (IBI), after the search array onset, showed an effect of the target, whereas the 2nd IBI also showed an effect of the distractors. The results suggest that controlled processing of the task operates together with automatic processing.     

Input and output in distributive theory

Distributive theories evaluate distributions of goods based on candidate recipients’ characteristics, e.g. how well off candidates are, how deserving they are, and whether they fare below sufficiency. But such characteristics vary across possible worlds, so distributive theories may differ in terms of the world which for them settles candidates’ characteristics. This paper examines how distributive theories differ in terms of whether candidate recipients’ relevant characteristics are grounded in the possible world that would take place if the distributor does not intervene (call it the “input” world) or if they are grounded in each possible world that the distributor can bring about through different decisions (call each an “output” world). We illustrate the importance of this distinction in relation to one distributive theory, prioritarianism. As we show, both input and output versions of prioritarianism are plausible interpretations of the literature, and there are good reasons to take input prioritarianism seriously. Ultimately, however, we argue that input prioritarianism should be rejected.     

A short note on the estimation of the asymptotic covariance matrix for polychoric correlations

By using a Taylor expansion of the equations that define the two step estimator for polychoric correlations, the asymptotic covariance matrix for the estimated correlations can be derived in a simple and straightforward way.