Sensitivity of psychiatric diagnosis based on the best estimate procedure

OBJECTIVE

A "best estimate" diagnosis is one made by expert clinicians on the basis of diagnostic information from direct interview conducted by another clinician plus information from medical records and from reports of family members. The authors address the question of whether the best estimate procedure can enhance the classification of psychiatric diagnoses of subjects who are interviewed directly.

METHOD

Four hundred seventy-five subjects were interviewed directly: 201 opiate-addicted probands who sought treatment from a university-based clinic and 274 of their spouses and/or first-degree relatives. Subjects were interviewed by trained clinical assessors using the Schedule for Affective Disorders and Schizophrenia and classified according to Research Diagnostic Criteria. Two psychologists independently diagnosed the same subjects by applying the best estimate procedure. Lifetime rates of major and minor depressive disorder, antisocial personality, alcoholism, and drug abuse were calculated. The rates of diagnoses made on the basis of direct interviews alone were compared with the rates of diagnoses made according to the best estimate procedure.

RESULTS

Higher rates of diagnoses of all four disorders were made when the best estimate procedure was applied than when direct interview alone was used; the best estimate procedure also resulted in a minimal rate of false positives.

CONCLUSIONS

The higher rate of diagnoses based on the best estimate procedure may represent an enhancement in the accuracy of psychiatric diagnoses or an increase in erroneous diagnoses. The authors consider the second possibility less likely.

Gender differences in cocaine use and treatment response

Much of our understanding of treatment efficacy in drug abuse is based on male drug abusers. In order to determine if there are gender differences in baseline drug use and treatment response, we compared male and female cocaine abusers who participated in an outpatient randomized clinical trial (RCT) evaluating pharmacotherapies for cocaine abuse. Although females had more severe drug problems at intake, they were as successful as males in the RCT and more successful at 6-month follow-up.

Stress effects in the hippocampus: synaptic plasticity and memory

It is now well-documented that exposures to uncontrollable (inescapable and unpredictable) stress in adulthood can have profound effects on brain and behavior. Converging lines of evidence from human and animal studies indicate that stress interferes with subsequent performances on a variety of hippocampal-dependent memory tasks. Animal studies further revealed that stress impedes ensuing induction of long-term potentiation (LTP) in the hippocampus. Because the hippocampus is important for key aspects of memory formation and because LTP has qualities congruent to an information storage mechanism, it is hypothesized that stress-induced modifications in hippocampal plasticity contribute to memory impairments associated with stress. Recent studies provide evidence that the amygdala, a structure important in stress- and emotion-related behaviors, plays a necessary role in the emergence of stress-associated changes in hippocampal LTP and memory. Early life stress also alters hippocampal plasticity and memory in a manner largely consistent with effects of adult stress exposure. This review focuses on endocrine-system-level mechanisms of stress effects in the hippocampus, and how stress, by altering the property of hippocampal plasticity, can subsequently influence hippocampal memory.

HPA axis function and drug addictive behaviors: insights from studies with Lewis and Fischer 344 inbred rats

Much research supports a link between stress and its concomitant hypothalamic-pituitary-adrenal (HPA) axis responses with behavioral sensitivity to psychoactive drugs. Our research demonstrates that Lewis inbred rats more readily acquire drug self-administration than Fischer 344 (F344) inbred rats and, compared to this strain, Lewis rats have hyporesponsive HPA axis responses to stress exposure. This association appears to conflict with investigations using outbred rats and suggests that the relationship between drug sensitivity and HPA axis responsiveness is more complicated than originally thought. It is essential to better understand this relationship because of its relevance to vulnerability and relapse to drug abuse. Thus, this paper reviews the literature in which these two inbred strains have been compared. We discuss strain differences in HPA axis function, in characteristics of the mesolimbic dopamine system, and in behaviors thought to reflect emotionality. Strain differences in unconditioned and conditioned effects of psychoactive drugs are then reviewed. Next, we discuss the possible role of sex and gonadal hormones on responsiveness to psychoactive drugs in these strains. Finally, a comparison of results obtained from these strains to three other comparator groups (e.g., high and low responders) suggests that a non-monotonic relationship between behavioral sensitivity to drugs and HPA axis responsiveness can explain much of the discrepancies in the literature.

Enhanced acquisition of cocaine self-administration in adult rats with neonatal isolation stress experience

That stress enhances the behavioral effects of cocaine is well-documented in adult rats, but whether early life stress endures into adulthood to affect responsivity to cocaine is less clear. We now report that neonatal isolation stress (1 h per day isolation on postnatal days 2-9) enhances acquisition of cocaine self-administration in adult rats. This effect was specific to cocaine and not due to learning or performance differences. Neither acquisition of operant responding for food nor locomotor activity differed between groups. These results have important implications for the role of early childhood stress in vulnerability to cocaine addiction.

Acquisition and maintenance of intravenous cocaine self-administration in Lewis and Fischer inbred rat strains

Lewis and Fischer inbred rat strains differ in behavioral and biochemical responses to psychoactive drugs: Lewis rats show greater behavioral responses to psychoactive drugs than Fischer rats and they fail to show biochemical adaptations in the mesolimbic dopamine system after chronic drug exposure, in contrast to Fischer and outbred rats. This suggests that Fischer and Lewis rats may differ in the initial, reinforcing effects of psychoactive drugs, but not in responses seen after the exposure that occurs with maintenance of drug-reinforced behavior. Thus, the present study tested whether these strains differ in acquisition or maintenance of intravenous cocaine self-administration. Acquisition of cocaine self-administration was examined in separate groups that were allowed 15 days to acquire the operant at one of three cocaine doses (0.25, 0.5, or 1.0 mg/kg/infusion). Compared to Fischer rats, Lewis rats acquired cocaine self-administration after fewer training trials and at lower doses. After maintenance, both strains showed characteristic extinction responding with saline substitution and dose-related responding to cocaine, although Fischer rats tended to show higher response rates. Finally, cocaine plasma levels, obtained after an intravenous cocaine infusion (1.0 mg/kg), showed no strain differences suggesting that the strain difference in acquisition was not due to cocaine pharmacokinetics. These strain differences in acquisition of cocaine self-administration may be related to reported strain differences in the mesolimbic dopamine system. Further, because acquisition of drug self-administration is an animal model of vulnerability to drug addiction, these inbred strains may be useful to study factors underlying such vulnerability.

Early life stress impairs fear conditioning in adult male and female rats

We demonstrated that neonatal isolation (1-h pup isolation; postnatal days 2-9) impairs context-induced fear conditioning in adult male rats and tends to enhance this effect and foot shock sensitivity in females. In this study, we examine the effects of brief (i.e., handling; 15 min) and prolonged (3 h) maternal separations (postnatal days 1-21) on fear conditioning and foot shock sensitivity in adult male and female rats. Identical training and test conditions from our prior study were employed so comparisons of the three early life stressors could be made. Context- and cue-elicited freezing and ultrasonic vocalizations (USVs; 22 kHz) were measured after 10 tone-shock training trials in Experiment 1. In Experiment 2, foot shock responses (flinch, jump, sonic vocalizations) to escalating shock levels were assessed. Brief maternal separation impaired context- and cue-conditioned fear in rats of both sexes as assessed by USVs. Prolonged maternal separation only impaired context fear in female rats. There were no effects on foot shock sensitivity. Results of this and other studies suggest that early life stress impairs fear conditioning in adult rats whereas stress experienced in adulthood has the opposite effect. These opposing effects may reflect developmental differences on stress-induced alterations on hippocampal regulation of the hypothalamic-pituitary-adrenal axis.

Fischer and Lewis rat strains differ in basal levels of neurofilament proteins and their regulation by chronic morphine in the mesolimbic dopamine system

We studied levels of neurofilament (NF) proteins in the ventral tegmental area (VTA), and other regions of the central nervous system, of two genetically inbred rat strains, Lewis (LEW) and Fischer (F344) rats. These strains represent genetically divergent populations of rats that have been used to study possible genetic factors involved in a variety of biological processes, including drug addiction: compared to F344 rats, LEW rats show a much higher preference for several classes of drugs of abuse. We found 30-50% lower levels of three NF proteins, NF-200 (NF-H), NF-160 (NF-M), and NF-68 (NF-L), in the VTA of LEW compared to F344 rats by use of immunolabeling and Coomassie blue staining. These strain differences were highly specific to this brain region, with no differences observed elsewhere in brain or spinal cord. Interestingly, chronic treatment of F344 rats with morphine decreased levels of these three NF proteins in the VTA, as found previously in outbred Sprague-Dawley rats (Beitner-Johnson, D., Guitart, X., and Nestler, E.J.:J. Neurosci., 12:2165-2176, 1992), whereas morphine had no effect on NF levels in the VTA of LEW rats. A similar strain difference was observed in chronic morphine regulation of tyrosine hydroxylase, with morphine increasing enzyme immunoreactivity in the VTA of F344 rats (as has been observed previously in Sprague-Dawley rats [Beitner-Johnson, D., and Nestler, E.J.:J. Neurochem., 57:344-347, 1991]), but not in LEW rats. In view of the observations that LEW and F344 rats show different levels of preference for several types of drugs of abuse, and of the evidence supporting a central role of the mesolimbic dopamine system in drug reward mechanisms, the results of the current study suggest the possibility that levels of NFs and tyrosine hydroxylase may mediate some aspects of drug reinforcement and contribute to individual genetic differences in vulnerability to drug addiction.

Repeated unpredictable stress and antidepressants differentially regulate expression of the bcl-2 family of apoptotic genes in rat cortical, hippocampal, and limbic brain structures

Apoptosis has been proposed as a contributing cellular mechanism to the structural alterations that have been observed in stress-related mood disorders. Antidepressants, on the other hand, are hypothesized to exert trophic and/or neuroprotective actions. The present study examined the regulation of the major antiapoptotic (Bcl-2, Bcl-xl) and proapoptotic (Bax) genes by repeated unpredictable stress (an animal model of depression) and antidepressant treatments (ADT). In adult rats, exposure to unpredictable stress reduced Bcl-2 mRNA levels in the central nucleus of the amygdala (CeA), cingulate (Cg), and frontal (Fr) cortices. Bcl-xl mRNA was significantly decreased in hippocampal subfields. In contrast, chronic administration of clinically effective antidepressants from four different classes, ie fluoxetine, reboxetine, tranylcypromine, and electroconvulsive seizures (ECS) upregulated Bcl-2 mRNA expression in the Cg, Fr, and CeA. Reboxetine, tranylcypromine, and ECS selectively increased Bcl-xl, but not Bcl-2 mRNA expression in the hippocampus. Chemical ADT but not ECS, robustly enhanced Bcl-2 expression in the medial amygdaloid nucleus and ventromedial hypothalamus. Fluoxetine did not influence Bcl-xl expression in the hippocampus, but it was the only ADT that decreased Bax expression in this region. In the CeA, again in direct contrast to the stress effects, exposure to all classes of ADTs significantly increased Bcl-2 mRNA. The selective regulation of Bcl-xl and Bax in hippocampal subfields and of Bcl-2 in the Cg cortex, amygdala, and hypothalamus suggests that these cellular adaptations contribute to the long-term neural plastic adaptations to stress and ADTs in cortical, hypothalamic, and limbic brain structures.

Prazosin, an alpha-1 adrenergic antagonist, reduces cocaine-induced reinstatement of drug-seeking

BACKGROUND

Norepinephrine is implicated in cocaine's behavioral effects. In this study, we tested the effect of prazosin, an alpha1-adrenergic receptor antagonist, on cocaine-induced reinstatement of drug-seeking behavior.

METHODS

Rats were trained to self-administer cocaine intravenously under a fixed-ratio 3 schedule of reinforcement. After behavior was established, cocaine was replaced with saline and behavior extinguished. The ability of cocaine (0, 5-20 mg/kg) alone or combined with prazosin (.3 mg/kg) to reinstate lever press responding was tested. The effects of prazosin on lever press responding for food was examined in another set of rats.

RESULTS

Cocaine induced a dose-dependent reinstatement of drug-seeking behavior that was significantly attenuated by prazosin. This dose of prazosin did not alter lever press response rates for food.

CONCLUSIONS

The attenuation in drug-induced reinstatement is likely not due to prazosin-induced suppression of activity. These results suggest alpha1-adrenergic mechanisms contribute to reinstatement in rats and perhaps, to relapse in addicts.

Chronic unpredictable stress, but not chronic predictable stress, enhances the sensitivity to the behavioral effects of cocaine in rats

RATIONALE

Chronic unpredictable stress, in which the type and timing of stress exposures are varied, alters protein levels in the mesolimbic DA system in a manner previously shown to be associated with enhanced behavioral responsiveness to cocaine. Chronic exposure to the same or predictable stress (restraint) does not. Thus, we examined the effects of chronic unpredictable and chronic predictable (restraint) stress on the locomotor activating and place conditioning effects to low cocaine doses.

OBJECTIVE

To test whether chronic unpredictable stress enhances the sensitivity to the behavioral effects of cocaine.

METHODS

Rats were exposed to 10 days of chronic unpredictable stress, of chronic predictable (restraint) stress, or were not stressed. One day following cessation of stress exposure, locomotor activity to cocaine (0 or 7.5 mg/kg) was assessed for 4 consecutive days and corticosterone levels on the last day were determined. In other experiments, the effects of the chronic stress procedures on cocaine (0.5 and 7.5 mg/kg) place conditioning using an unbiased procedure were assessed.

RESULTS

Chronic unpredictable, but not chronic predictable, stress transiently increased the locomotor activating effects of cocaine and this was correlated positively with corticosterone levels. Chronic unpredictable, but not chronic predictable, stress also enhanced the place conditioning effects of cocaine: increased place preference was seen with the low dose and a pronounced place aversion occurred with the high dose.

CONCLUSIONS

These data demonstrate that chronic unpredictable stress enhances the behavioral effects of cocaine, including its aversive effects, whereas chronic predictable stress (restraint) is without effect.

Cognitive and serum BDNF correlates of BDNF Val66Met gene polymorphism in patients with schizophrenia and normal controls

Studies suggest that a functional polymorphism of the brain-derived neurotrophic factor gene (BDNF Val66Met) may mediate hippocampal-dependent cognitive functions. A few studies have reported its role in cognitive deficits in schizophrenia including its association with peripheral BDNF levels as a mediator of these cognitive deficits. We assessed 657 schizophrenic inpatients and 445 healthy controls on the repeatable battery for the assessment of neuropsychological status (RBANS), the presence of the BDNF Val66Met polymorphism and serum BDNF levels. We assessed patient psychopathology using the Positive and Negative Syndrome Scale. We showed that visuospatial/constructional abilities significantly differed by genotype but not genotype × diagnosis, and the Val allele was associated with better visuospatial/constructional performance in both schizophrenic patients and healthy controls. Attention performance showed a significant genotype by diagnosis effect. Met allele-associated attention impairment was specific to schizophrenic patients and not shown in healthy controls. In the patient group, partial correlation analysis showed a significant positive correlation between serum BDNF and the RBANS total score. Furthermore, the RBANS total score showed a statistically significant BDNF level × genotype interaction. We demonstrated an association between the BDNF Met variant and poor visuospatial/constructional performance. Furthermore, the BDNF Met variant may be specific to attentional decrements in schizophrenic patients. The association between decreased BDNF serum levels and cognitive impairment in schizophrenia is dependent on the BDNF Val66Met polymorphism.

Dual modulation of endocannabinoid transport and fatty acid amide hydrolase protects against excitotoxicity

The endocannabinoid system has been suggested to elicit signals that defend against several disease states including excitotoxic brain damage. Besides direct activation with CB1 receptor agonists, cannabinergic signaling can be modulated through inhibition of endocannabinoid transport and fatty acid amide hydrolase (FAAH), two mechanisms of endocannabinoid inactivation. To test whether the transporter and FAAH can be targeted pharmacologically to modulate survival/repair responses, the transport inhibitor N-(4-hydroxyphenyl)-arachidonamide (AM404) and the FAAH inhibitor palmitylsulfonyl fluoride (AM374) were assessed for protection against excitotoxicity in vitro and in vivo. AM374 and AM404 both enhanced mitogen-activated protein kinase (MAPK) activation in cultured hippocampal slices. Interestingly, combining the distinct inhibitors produced additive effects on CB1 signaling and associated neuroprotection. After an excitotoxic insult in the slices, infusing the AM374/AM404 combination protected against cytoskeletal damage and synaptic decline, and the protection was similar to that produced by the stable CB1 agonist AM356 (R-methanandamide). AM374/AM404 and the agonist also elicited cytoskeletal and synaptic protection in vivo when coinjected with excitotoxin into the dorsal hippocampus. Correspondingly, potentiating endocannabinoid responses with the AM374/AM404 combination prevented behavioral alterations and memory impairment that are characteristic of excitotoxic damage. The protective effects mediated by AM374/AM404 were (1) evident 7 d after insult, (2) correlated with the preservation of CB1-linked MAPK signaling, and (3) were blocked by a selective CB1 antagonist. These results indicate that dual modulation of the endocannabinoid system with AM374/AM404 elicits neuroprotection through the CB1 receptor. The transporter and FAAH are modulatory sites that may be exploited to enhance cannabinergic signaling for therapeutic purposes.

Strain-selective effects of corticosterone on locomotor sensitization to cocaine and on levels of tyrosine hydroxylase and glucocorticoid receptor in the ventral tegmental area

We have studied biochemical and behavioral effects of chronic corticosterone administration in two inbred rat stains (Fischer 344 and Lewis), known to differ in their hypothalamic-pituitary-adrenal axis and in their behavioral responses to drugs of abuse. First, we studied corticosterone regulation of phosphoproteins in the ventral tegmental area of sham- and corticosterone-treated Fischer and Lewis rats, by means of back-phosphorylation and two-dimensional gel electrophoresis and Western blotting analysis. Corticosterone administration upregulated tyrosine hydroxylase immunoreactivity and decreased glial-fibrillary acidic protein phosphorylation state in the ventral tegmental area of Fischer rats only, with no changes seen in Lewis rats. We also studied corticosterone effects on locomotor sensitization to cocaine, a behavior known to be regulated by the ventral tegmental area. In Fischer rats, chronic corticosterone pretreatment resulted in development of cocaine sensitization, which was absent in sham-pretreated Fischer rats. In contrast, Lewis rats developed cocaine sensitization either with or without corticosterone pretreatment. Thus, both biochemical and behavioral effects of corticosterone observed in Fischer rats were absent in Lewis rats. We next studied the possibility that certain transcription factors, thought to play a role in tyrosine hydroxylase expression, could be involved in these strain-selective effects of corticosterone. Corticosterone treatment decreased levels of glucocorticoid receptor immunoreactivity in the ventral tegmental area of Lewis rats, but not of Fischer rats. In addition, drug-naive Fischer rats showed higher ventral tegmental area levels of immunoreactivity of cyclic AMP response element binding protein than Lewis rats, with no effect of corticosterone observed in either strain. These findings suggest that hypothalamic-pituitary-adrenal axis modulation of responses to drugs of abuse is a genetically determined characteristic seen in Fischer rats, but absent in Lewis rats. We propose that corticosterone administration down-regulates the glucocorticoid receptor in the ventral tegmental area of Lewis rats, and thereby prevents other adaptations to corticosterone treatment, while in the ventral tegmental area of Fischer rats the lack of glucocorticoid receptor down-regulation and the high basal levels of cyclic AMP response element binding protein could facilitate the transcriptional, biochemical and behavioral actions of glucocorticoids.

Gender differences in never-medicated first-episode schizophrenia and medicated chronic schizophrenia patients

BACKGROUND

Schizophrenia shows gender differences in patients' clinical presentation, neurocognitive impairment, course, and treatment outcome. The aims of this study were to compare gender differences in clinical features and cognitive functioning in first-episode and chronic schizophrenia among Han Chinese inpatients.

METHOD

We compared gender differences in 262 unmedicated first-episode schizophrenia and 960 chronic schizophrenia inpatients (diagnosed according to DSM-IV) to 804 matched healthy controls on sociodemographic characteristics, smoking behavior, and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Patients were also rated on the Positive and Negative Syndrome Scale. The study was conducted from December 2006 to May 2008.

RESULTS

Schizophrenia first occurred in both first-episode and chronic schizophrenia patients at a significantly earlier age in male than female patients (P < .05 and P < .001, respectively). The paranoid subtype of schizophrenia was more common in female patients only in chronic schizophrenia, not first-episode patients. Further, cigarette smoking was more common in male than female patients from both patient groups, and, among men, more chronic schizophrenia patients than controls smoked, while among women, fewer chronic schizophrenia patients than controls smoked. Female chronic schizophrenia patients had more severe positive and general psychopathological symptoms, whereas male patients had more severe negative symptoms. By contrast, first-episode schizophrenia patients showed no gender differences in symptoms and severity. Both first-episode and chronic schizophrenia patients performed worse than controls on most of the cognitive tasks. RBANS attention, delayed memory, and immediate memory were less impaired in female than male chronic schizophrenia patients, and first-episode schizophrenia patients showed no gender differences.

CONCLUSIONS

Chronic schizophrenia patients have notable gender differences in the age at onset, smoking, symptom severity, and cognitive function favoring women, but first-episode schizophrenia patients show few gender differences.

BDNF levels and genotype are associated with antipsychotic-induced weight gain in patients with chronic schizophrenia

Recent evidence suggests that centrally released brain-derived neurotrophic factor (BDNF) modulates eating behavior and metabolism that is responsible for body weight fluctuation. BDNF also may play an important role in the therapeutic action of antipsychotic medications. We investigated whether the Val66Met polymorphism of the BDNF gene affected weight gain after long-term antipsychotic treatment in schizophrenia. The polymorphism was genotyped in 196 Chinese patients with schizophrenia on long-term antipsychotic medication. Serum BDNF was measured in all patients and 50 normal controls. Mean body mass index (BMI) change was evaluated retrospectively by means of clinical records. The results showed that there was a significant relationship between the three BDNF Val/Met genotypes and mean BMI gain, with genotype having a strong effect on BMI gain in male but not female patients. BDNF levels were significantly lower in patients than normal controls, and negatively correlated with BMI gain in female but not male patients. Our results suggest that variation in the BDNF gene may be a risk factor for weight gain in male patients with schizophrenia on long-term antipsychotic treatment, and decreased BDNF levels may be associated with weight gain in females.

Depressive symptoms during buprenorphine treatment of opioid abusers

Among 40 opioid addicts treated as outpatients with sublingual buprenorphine (2-8 mg daily) for a month, depressive symptoms significantly decreased in the 19 who were depressed at intake to treatment.

Differential behavioral responses to cocaine are associated with dynamics of mesolimbic dopamine proteins in Lewis and Fischer 344 rats

Differential behavioral and biochemical responses to drugs of abuse may reflect genetic makeup as suggested by studies of inbred Lewis (LEW) and Fischer 344 (F344) rats. We investigated locomotor activity, stereotypy signs, and levels of specific proteins in the nucleus accumbens (NAc) and ventral tegmental area (VTA) in these strains at baseline and following chronic administration of cocaine (30 mg/kg/day for 14 days). Using Western blot analysis, we replicated our previous findings of baseline strain differences and found lower levels of DeltaFosB immunoreactivity in NAc of F344 vs. LEW rats. F344 rats showed greater baseline locomotor activity, sniffing, and grooming compared to LEW rats. Chronic cocaine increased DeltaFosB levels in NAc in both strains, whereas adaptations in other proteins were induced in F344 rats only. These included reduced levels of tyrosine hydroxylase (TH) in NAc and increased TH and glial fibrillary acidic protein (GFAP) immunoreactivity in VTA. Chronic cocaine led to greater increases in overall stereotypy in F344 vs. LEW rats and decreased exploratory behaviors in LEW rats. Opposing effects by strain were seen in locomotor activity. Whereas F344 rats showed higher initial activity levels that decreased with cocaine exposure (tolerance), LEW rats showed increased activity over days (sensitization) with no strain differences seen at 14 days. Further, conditioned locomotor activation to vehicle injections was greater in F344 vs. LEW rats. These results suggest that behavioral responsiveness to chronic cocaine exposure may reflect dynamics of mesolimbic dopamine protein levels and demonstrate the role of genetic background in responsiveness to cocaine.

Neonatal isolation enhances acquisition of cocaine self-administration and food responding in female rats

We showed previously that neonatal isolation (ISO) enhances acquisition of cocaine self-administration in adult male rats without altering acquisition of food responding. Female rats show poorer performance in learning tasks and are differentially affected by stress compared to male rats. Thus, we investigated whether ISO alters acquisition of operant responding for cocaine and food in female rats with comparison to male rats. Litters were subjected to ISO or were non-handled (NH). Activity levels were assessed in adult rats. Then, rats were implanted with jugular catheters and allowed to self-administer cocaine under a fixed-ratio 1 (FR1) schedule of reinforcement using an escalating dose presentation procedure. Cocaine intake, discrimination of active versus inactive levers, and ineffective active lever responses were tabulated. Effects of non-contingent cocaine infusions (primes) and increasing FR on responding were then assessed. Other rats were allowed to lever press for food under an FR1 schedule (10 s time-out). ISO enhanced acquisition of operant responding for food and cocaine in female rats. The latter was demonstrated by better lever discrimination, emission of fewer ineffective responses, and superior performance in response to primes. Yet, NH females ingested more cocaine than ISO females during the initial acquisition phase. In male rats, ISO enhanced acquisition of cocaine self-administration but not food responding. Activity levels were unaffected by ISO or gender. These data confirm and extend our previous findings demonstrating the enduring effects of ISO on adult self-administration behavior and emphasize the importance of measuring behavioral patterns versus intake in acquisition studies.

Sex-selective effects of neonatal isolation on fear conditioning and foot shock sensitivity

Our previous work demonstrates enduring effects of the early life stress of neonatal isolation (ISO). ISO facilitates appetitive response learning in adult female, but not male rats, and enhances corticosterone levels and stress responsivity in infant and juvenile rats of both sexes. Corticosterone acts at brain areas such as hippocampus that are rich in glucocorticoid receptors, differentiate postnatally, are sexually dimorphic, and involved in learning. Thus, ISO is hypothesized to alter aversive learning in adult rats in a sex-specific manner. This study tests this hypothesis using context and cue fear conditioning. Pups were isolated for 1h a day on postnatal (PN) days 2-9 or were non-handled and were then tested in adulthood (PN70-90). In Experiment 1, context- and cue-elicited freezing and ultrasonic vocalizations (USVs; 22 kHz range) were measured. Experiments 2-4, respectively, examined three unconditioned foot shock responses (flinch, jump, vocalization), unconditioned fear (time in center of an open, novel arena), and appetitive (stroking-induced; 50 kHz range) USVs. ISO had a sex-selective effect on context-induced USVs that may reflect changes in foot shock sensitivity. ISO increases foot shock sensitivity and tends to enhance context-induced fear in female rats, whereas ISO tends to impair context-induced fear in male rats. Overall, male rats show greater conditioned fear, and female rats show greater unconditioned fear as well as enhanced responses to the aversive and appetitive stimuli. The sex-specific effect of ISO on context fear may reflect neuronal reorganization in stress responsive areas and/or sex differences in some unconditioned responses.

Serum BDNF levels and weight gain in schizophrenic patients on long-term treatment with antipsychotics

Several lines of evidence suggest that central brain-derived neurotrophic factor (BDNF) modulates food intake, metabolism, and increases in body weight. Reports have also shown that serum BDNF is altered in schizophrenic patients treated with antipsychotics. This study aimed to determine if there was a relationship between BDNF and antipsychotic-induced weight gain in patients with chronic schizophrenia. Serum BDNF was measured in 124 schizophrenia patients chronically treated with clozapine (n=57), risperidone (n=23) or typical antipsychotics (n=44) and 50 healthy control subjects. To further assess group differences in serum BDNF, additional analyses were performed in a subset of patients and controls individually matched for body mass index (BMI). BDNF levels were lower in patients with schizophrenia than normal controls. However, this difference was not present when controlling for current BMI. In the individually BMI-matched sample, no differences in serum BDNF levels were observed in schizophrenic patients compared to BMI-matched healthy controls. BDNF levels negatively correlated with BMI gain in female but not in male patients when gender was considered. Antipsychotic class exerted differential effects over BDNF levels and BMI gain. Our findings suggest that decreased BDNF levels may be associated with weight gain in female schizophrenic patients on long-term antipsychotic treatment.

Superoxide dismutase and cytokines in chronic patients with schizophrenia: association with psychopathology and response to antipsychotics

OBJECTIVE

Both schizophrenia and oxidative stress have been associated with immune system abnormalities in interleukin-2 and -6 (IL-2; IL-6) and increases in superoxide dismutase (SOD) activity. These abnormalities may improve during antipsychotic drug treatment that reduces symptoms in schizophrenic patients.

MATERIALS AND METHODS

Subjects included 30 healthy controls (HC) and 78 schizophrenic (SCH) in-patients who were randomly assigned to 12 weeks of double-blind treatment with risperidone 6 mg/day or haloperidol 20 mg/day. Ratings using the Positive and Negative Syndrome Scale (PANSS) were correlated with blood SOD and serum IL-2 levels.

RESULTS

SCH patients who were medication-free for 2 weeks had greater SOD, IL-2, and IL-6 levels than HC. At baseline, these SOD elevations were associated with higher PANSS total scores and the IL-2 elevations with lower PANSS positive symptom scores. The SOD and IL-2 levels in the SCH were also positively correlated. After treatment, PANSS positive symptoms and both SOD and IL-2 showed a significant decrease, but IL-6 showed no change. The SOD and IL-2 reductions were correlated with the reductions in PANSS total score, and SOD reductions also correlated with positive subscore reductions. Females showed these associations more strongly than males.

CONCLUSION

Our results suggest that the dysregulation in the cytokine system and oxidative stress in patients with schizophrenia is implicated in clinical symptoms and is improved at least partially with antipsychotic treatment. The stronger associations in females deserve further study and confirmation.

Short-term tropisetron treatment and cognitive and P50 auditory gating deficits in schizophrenia

OBJECTIVE

The α7 nicotinic acetylcholine receptor (nAChR) is associated with cognitive and P50 auditory gating deficits in schizophrenia, and α7 nAChR agonists can potentially reverse these deficits. The authors examined multiple dosages of tropisetron, a partial agonist at the nAChR, for short-term effects on cognition and P50 deficits in schizophrenia.

METHOD

In a randomized double-blind design, 40 nonsmoking patients with schizophrenia who had P50 ratios greater than 0.5 and were stabilized on 3-6 mg/day of risperidone were randomly assigned to receive placebo (N=10) or oral tropisetron at 5 mg/day (N=10), 10 mg/day (N=10), or 20 mg/day (N=10). The authors measured P50 inhibitory gating and administered the Chinese-language version of the Repeatable Battery for the Assessment of Neuropsychological Status at baseline and after 10 days of treatment.

RESULTS

After 10 days of treatment, all three daily doses of tropisetron significantly improved overall cognitive deficits, with 10 mg showing the greatest improvement for the immediate memory index score and 20 mg for the delayed memory index score on the cognitive battery. The P50 deficits were also improved, and that improvement was significantly correlated with cognitive improvement. Two patients in the 20 mg/day group dropped out because of adverse effects, but the other dosages were well tolerated.

CONCLUSIONS

The improvement of cognition with tropisetron appeared to be associated with normalization in P50 deficits. Thus, α7 nAChR agonists appear to be a promising therapeutic approach for the treatment of cognitive deficits that are related to abnormal P50 suppression in schizophrenia.

Plasma total antioxidant status and cognitive impairments in schizophrenia

Oxidative stress-induced damage to neurons may contribute to cognitive deficits during aging and in neurodegenerative disorders. Schizophrenia has a range of cognitive deficits that may evolve from oxidative stress, and this study examines this association of oxidative stress with cognitive deficits in schizophrenia. We recruited 296 chronic schizophrenia patients and 181 healthy control subjects and examined the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and plasma total antioxidant status (TAS) in both groups. Schizophrenia symptoms were assessed using the positive and negative syndrome scale (PANSS). Our results showed that TAS levels were significantly lower in patients than controls (179.6 ± 81.0 U/ml vs. 194.8 ± 46.0 U/ml, p<0.05). Cognitive scores on the RBANS and nearly all of its five subscales (all p<0.001) except for the Visuospatial/Constructional index (p>0.05) were significantly lower in schizophrenia patients than normal controls. For the patients, TAS was inversely associated with some domains of cognitive deficits in schizophrenia, such as Attention and Immediate Memory. Our findings suggest that oxidative stress may be involved in the pathophysiology of schizophrenia, and its associated cognitive impairment.