Minimum information about a microarray experiment (MIAME)-toward standards for microarray data

Microarray analysis has become a widely used tool for the generation of gene expression data on a genomic scale. Although many significant results have been derived from microarray studies, one limitation has been the lack of standards for presenting and exchanging such data. Here we present a proposal, the Minimum Information About a Microarray Experiment (MIAME), that describes the minimum information required to ensure that microarray data can be easily interpreted and that results derived from its analysis can be independently verified. The ultimate goal of this work is to establish a standard for recording and reporting microarray-based gene expression data, which will in turn facilitate the establishment of databases and public repositories and enable the development of data analysis tools. With respect to MIAME, we concentrate on defining the content and structure of the necessary information rather than the technical format for capturing it.

Dopamine transmission in the initiation and expression of drug- and stress-induced sensitization of motor activity

Progress has been made over the last 10 years in determining the neural mechanisms of sensitization induced by amphetamine-like psychostimulants, opioids and stressors. Changes in dopamine transmission in axon terminal fields such as the nucleus accumbens appear to underlie the expression of sensitization, but the actions of drugs and stressors in the somatodendritic regions of the A10/A9 dopamine neurons seem critical for the initiation of sensitization. Manipulations that increase somatodendritic dopamine release and permit the stimulation of D1 dopamine receptors in this region induce changes in the dopamine system that lead to the development of long-term sensitization. However, it is not known exactly how the changes in the A10/A9 region are encoded to permit augmented dopamine transmission in the terminal field. One possibility is that the dopamine neurons of sensitized animals have become increasingly sensitive to excitatory pharmacological and environmental stimuli or desensitized to inhibitory regulation. Alternatively, changes in cellular activity or protein synthesis may result in a change in the presynaptic regulation of axon terminal dopamine release.

Interaction of tyrosine-based sorting signals with clathrin-associated proteins

Tyrosine-based signals within the cytoplasmic domain of integral membrane proteins mediate clathrin-dependent protein sorting in the endocytic and secretory pathways. A yeast two-hybrid system was used to identify proteins that bind to tyrosine-based signals. The medium chains (mu 1 and mu 2) of two clathrin-associated protein complexes (AP-1 and AP-2, respectively) specifically interacted with tyrosine-based signals of several integral membrane proteins. The interaction was confirmed by in vitro binding assays. Thus, it is likely that the medium chains serve as signal-binding components of the clathrin-dependent sorting machinery.

Reinstatement of cocaine-reinforced responding in the rat

Non-contingent "priming" drug injections and conditioned stimuli associated with drug injections led to reinstatement of responding after a period of extinction. Rats implanted with intravenous catheters were trained to self-administer cocaine 1 mg/kg/injection), and then given daily test sessions consisting of a period of self-administration followed by extinction conditions. Test drug injections or conditioned stimuli were presented during extinction and the latency to the first response and the total number of responses following the treatment were measured. Cocaine injections of 0.5, 1.0, and 2.0 mg/kg restored responding during extinction, regardless of the duration of the extinction period (between 10 min and 180 min) since drug self-administration. Amphetamine, apomorphine, and morphine but not ethanol, heroin, or methohexital reinstated previously cocaine-reinforced responding. Amphetamine, cocaine, and morphine did not increase responding in animals trained to bar press only for food reinforcement, suggesting that the reinstatement effect is specific to drug-reinforced responses. The statement effect is specific to drug-reinforced responses. The final experiment showed that a tone that had been paired with drug infusions acquired a statistically significant tendency to facilitate responding when tested during extinction but this effect disappeared after the first test presentation of the tone.

Estimates of the prevalence of acute stroke impairments and disability in a multiethnic population

BACKGROUND AND PURPOSE

The goals of the present study were to estimate the prevalence of acute impairments and disability in a multiethnic population of first-ever stroke and to identify differences in impairment and early disability between pathological and Bamford subtypes. Associations between impairments and death and disability at 3 months were identified.

METHODS

Impairments that occur at the time of maximum neurological deficit were recorded, and disability according to the Barthel Index (BI) was assessed 1 week and 3 months after stroke in patients in the South London Stroke Register:

RESULTS

Of 1259 registered patients, 6% had 1 or 2, 31.1% had 3 to 5, 50.6% had 6 to 10, and 10.6% had >10 impairments. Common impairments were weakness (upper limb, 77.4%), urinary incontinence (48.2%), impaired consciousness (44.7%), dysphagia (44.7%), and impaired cognition (43.9%). Patients with total anterior circulation infarcts had the highest age-adjusted prevalence of weakness, dysphagia, urinary incontinence, cognitive impairment, and disability. Patients with subarachnoid hemorrhage had the highest rates of coma. Patients with lacunar stroke had the high prevalence of weakness but were least affected by disability, incontinence, and cognitive dysfunction. Blacks had higher age- and sex-adjusted rates of disability in ischemic stroke (BI <20, odds ratio 2.76, 95% CI 1.47 to 5.21, P=0.002; BI <15, odds ratio 1.8, 95% CI 1.45 to 2.81, P=0.01) but impairment rates similar to those of whites. On multivariable analysis, incontinence, coma, dysphagia, cognitive impairment, and gaze paresis were independently associated with severe disability (BI <10) and death at 3 months.

CONCLUSIONS

The extent of these findings indicates that an acute assessment of impairments and disability is necessary to determine the appropriate nursing and rehabilitation needs of patients with stroke.

Antimicrobial properties of plant essential oils and essences against five important food-borne pathogens

The antimicrobial properties of 21 plant essential oils and two essences were investigated against five important food-borne pathogens, Campylobacter jejuni, Salmonella enteritidis, Escherichia coli, Staphylococcus aureus and Listeria monocytogenes. The oils of bay, cinnamon, clove and thyme were the most inhibitory, each having a bacteriostatic concentration of 0.075% or less against all five pathogens. In general, Gram-positive bacteria were more sensitive to inhibition by plant essential oils than the Gram-negative bacteria. Campylobacter jejuni was the most resistant of the bacteria investigated to plant essential oils, with only the oils of bay and thyme having a bacteriocidal concentration of less than 1%. At 35 degrees C, L. monocytogenes was extremely sensitive to the oil of nutmeg. A concentration of less than 0.01% was bacteriostatic and 0.05% was bacteriocidal, but when the temperature was reduced to 4 degrees, the bacteriostatic concentration was increased to 0.5% and the bacteriocidal concentration to greater than 1%.

Stress-induced relapse to heroin and cocaine seeking in rats: a review

Studies in humans suggest that exposure to stress increases the probability of relapse to drug use, but until recently there has been no animal model to study the mechanisms that mediate this effect. We have developed a reinstatement procedure that allows us to study the effect of stress on relapse to drug seeking in rats. Using this procedure, we have shown that exposure to intermittent footshock stress reliably reinstates heroin and cocaine seeking after prolonged drug-free periods. In the present paper, we summarize results from several studies on stress-induced reinstatement of heroin and cocaine seeking in rats. We first assess the degree to which the phenomenon of stress-induced relapse generalizes to other stressors, to behaviors controlled by other drugs of abuse, and to behaviors controlled by non-drug reinforcers. We then review evidence from studies concerned with the neurotransmitters, the brain sites, and the neural systems involved in stress-induced reinstatement of drug seeking. Finally, we consider the mechanisms that might underlie stress-induced relapse to drug seeking and the possible implications of the findings for the treatment of relapse to drug use in humans.

Radiation injury to the heart

For the RTOG Consensus Conference on Late Effects of Cancer Treatment we summarize the clinical manifestations of cardiac complications appearing months to years following incidental irradiation of the heart during treatment of thoracic neoplasms. The most common effects present as pericardial disease, however, it is becoming more clear that precocious or accelerated coronary artery disease is an important late effect, especially in patients treated with radiation before the age of 21 years. To the extent it is known, the pathophysiology of the various syndromes is described and the extensive literature on dose, volume, and fractionation factors is reviewed. Based upon our current understanding of late cardiac effects, a clinical grading system has been developed and is published elsewhere in this issue.

Routine follow up of breast cancer in primary care: randomised trial

OBJECTIVE

To assess the effect on time to diagnosis of recurrence and on quality of life of transferring primary responsibility for follow up of women with breast cancer in remission from hospital to general practice.

DESIGN

Randomised controlled trial with 18 month follow up in which women received routine follow up either in hospital or in general practice.

SUBJECTS AND SETTING

296 women with breast cancer in remission receiving regular follow up care at district general hospitals in England.

MAIN OUTCOME MEASURES

Time between first presentation of symptoms to confirmation of recurrence; quality of life measured by specific dimensions of the SF-36 schedule, the EORTC symptom scale, and hospital anxiety and depression scale.

RESULTS

Most recurrences (18/26, 69%) presented as interval events, and almost half (7/16, 44%) of the recurrences in the hospital group presented first to general practice. The median time to hospital confirmation of recurrence was 21 days in the hospital group (range 1-376 days) and 22 days in the general practice group (range 4-64). The differences between groups in the change in SF-36 mean scores from baseline were small: -1.8 (95% confidence interval -7.2 to 3.5) for social functioning, 0.5 (-4.1 to 5.1) for mental health, and 0.6 (-3.6 to 4.8) for general health perception. The change from baseline in the mean depression score was higher in the general practice group at the mid-trial assessment (difference 0.6, 0.1 to 1.2) but there was no significant difference between groups in the anxiety score or the EORTC scales.

CONCLUSION

General practice follow up of women with breast cancer in remission is not associated with increase in time to diagnosis, increase in anxiety, or deterioration in health related quality of life. Most recurrences are detected by women as interval events and present to the general practitioner, irrespective of continuing hospital follow up.

Stress reinstates cocaine-seeking behavior after prolonged extinction and a drug-free period

We have shown previously, using an animal model of relapse, that acute exposure to intermittent footshock stress induces reinstatement of heroin-taking behavior in rats. Here we report that in rats trained to self-administer cocaine, exposure to acute intermittent footshock stress induces reinstatement of cocaine-taking behavior after prolonged extinction sessions and after a 4- to 6-week drug-free period; an effect comparable to that induced by a priming injection of cocaine. Animals were initially allowed to self-administer cocaine HCl (1.0 mg/kg per infusion, i.v.) during one 3-h session/day for 12 days. Subsequently, extinction conditions were introduced by substituting saline for cocaine so that lever-pressing resulted in i.v. infusions of saline rather than of drug. Extinction conditions were maintained until animals made 15 responses or less in the 3 h, after which animals were given saline infusions at the start of each daily session to establish baseline responding of ten responses or less. Subsequently, animals were tested for reinstatement of responding for saline infusions following a non-contingent injection of cocaine (2.0 mg/kg, i.v.) and exposure to intermittent footshock (10 min, 0.5 mA, 0.5 s on, mean off period of 40 sec). After an additional 4- to 6-week drug-free period, tests for reinstatement were repeated. Reinstatement of cocaine-taking behavior was observed in both sets of tests in response to footshock and cocaine. These results extend previous reports from this laboratory that footshock stress is an effective stimulus for reinstatement of drug-taking behavior in the rat.

Effect of computer support on younger women with breast cancer

OBJECTIVE

Assess impact of a computer-based patient support system on quality of life in younger women with breast cancer, with particular emphasis on assisting the underserved.

DESIGN

Randomized controlled trial conducted between 1995 and 1998.

SETTING

Five sites: two teaching hospitals (Madison, Wis, and Chicago, Ill), two nonteaching hospitals (Chicago), and a cancer resource center (Indianapolis, Ill). The latter three sites treat many underserved patients.

PARTICIPANTS

Newly diagnosed breast cancer patients (N = 246) under age 60.

INTERVENTIONS

Experimental group received Comprehensive Health Enhancement Support System (CHESS), a home-based computer system providing information, decision-making, and emotional support.

MEASUREMENTS AND MAIN RESULTS

Pretest and two post-test surveys (at two- and five-month follow-up) measured aspects of participation in care, social/information support, and quality of life. At two-month follow-up, the CHESS group was significantly more competent at seeking information, more comfortable participating in care, and had greater confidence in doctor(s). At five-month follow-up, the CHESS group had significantly better social support and also greater information competence. In addition, experimental assignment interacted with several indicators of medical underservice (race, education, and lack of insurance), such that CHESS benefits were greater for the disadvantaged than the advantaged group.

CONCLUSIONS

Computer-based patient support systems such as CHESS may benefit patients by providing information and social support, and increasing their participation in health care. These benefits may be largest for currently underserved populations.

Stress reinstates heroin-seeking in drug-free animals: an effect mimicking heroin, not withdrawal

Exposure to 10 min of footshock stress (1 mA; 0.5 s on, with a mean off period of 40 s) reinstated heroin-seeking behavior in heroin-experienced, drug-free rats after many sessions of extinction and up to 6 weeks after last exposure to heroin. In reinstating the behavior, the footshock mimicked the effect of a non-contingent priming infusion of heroin (50 micrograms/kg). By contrast, the aversive state of acute opioid withdrawal induced by injection of the opioid receptor antagonist naltrexone (5 mg/kg, SC), following an acute injection of morphine (10 mg/kg, SC), had no effect on heroin-seeking behavior. In a second experiment it was shown in drug naive animals that these parameters of footshock increased dopamine overflow in the nucleus accumbens, a terminal region of the mesolimbic dopamine system implicated in the reinforcing effects of drugs. Similarly, dopamine overflow was increased by an injection of 10 mg/kg morphine, SC, an effect that was reversed by an injection of 5 mg/kg naltrexone given 40 min after to induce the withdrawal condition. A possible interpretation of the present results is that stressors can reinstate drug-taking behavior by activating neural systems in common with those activated by heroin.

Survival of subendocardial Purkinje fibers after extensive myocardial infarction in dogs

Alterations in cardiac electrophysiology that accompany myocardial infarction were studied in dogs subjected to a two-stage ligation of the anterior descending coronary artery. A multipolar transmural needle electrode was used to record electrical activity from the in situ infarcted heart 24 hours after coronary occlusion. Bipolar electrograms recorded from subendocardial regions of infarcted myocardium demonstrated the persistence of early, rapid deflections suggesting Purkinje fiber activity; evidence of ventricular muscle activity in the infarct was absent in both subendocardial and intramural electrograms. The infarcted myocardium and the adjacent non-infarcted tissue were then excised and studied with intracellular microelectrodes in vitro. Transmembrane action potentials could be recorded from one or two cell layers of subendocardial Purkinje fibers at all sites within the infarcted region, but no ventricular muscle action potentials were found. Subendocardial Purkinje fibers which survived in the infarct had reduced maximum diastolic potentials, action potential amplitudes, and maximum depolarization velocities compared with normal subendocardial Purkinje fibers; also, action potential durations in these surviving fibers were extraordinarily prolonged. Spontaneous diastolic depolarization was evident in some surviving fibers. Since subendocardial Purkinje fibers that generate abnormal action potentials survive in an infarct, these fibers may participate in the genesis of ventricular arrhythmias that accompany infarction.

Cocaine-induced conditioned place preference: reinstatement by priming injections of cocaine after extinction

To explore the way in which drugs act to reinstate drug-seeking behavior, we studied drug-induced reinstatement of a cocaine-induced conditioned place preference (CPP). In a series of experiments, we studied the establishment, maintenance, extinction and reinstatement of a cocaine-induced CPP in a three-chamber 'unbiased' apparatus. Groups of rats were given four 20-min pairings of one chamber with cocaine (10.0 mg/kg, i.p.) and four of the other with saline on alternate days. In 15-min tests for CPP, drug-free rats were placed in the center choice chamber with access to the entire apparatus. Experiments were designed to study the expression of the CPP, the maintenance of the CPP in tests given at 2, 4, and 6 weeks after training, and the reinstatement of the CPP by cocaine (5.0 mg/kg) after extinction by 12 repeated tests in the non-drugged state, and after extinction by pairing each chamber, on alternate days, with saline on four occasions. Robust CPPs were obtained that endured for 4 weeks and were maintained for up to 6 weeks when tests were given at 2-week intervals. Both extinction procedures led to the loss of the CPP that was in turn reinstated by priming injections of cocaine. These results indicate that a cocaine-induced CPP, once developed, endures for several weeks, and is maintained by occasional testing even in the absence of additional drug experience. The fact that the CPP is easily reinstated when testing is preceded by a priming injection of cocaine suggests that drugs may induce relapse by renewing the incentive value of drug-associated cues.

A role for the CRF-containing pathway from central nucleus of the amygdala to bed nucleus of the stria terminalis in the stress-induced reinstatement of cocaine seeking in rats

RATIONALE

We reported previously that bilateral injection of a corticotropin-releasing factor (CRF)-receptor antagonist, D-Phe CRF(12-41), into the bed nucleus of the stria terminalis (BNST) blocks the reinstatement of cocaine seeking induced by footshock, whereas the injection of CRF into the same region induces reinstatement. One source of CRF in the BNST arises from a CRF-containing projection originating in the central nucleus of the amygdala (CeA).

OBJECTIVE

To determine whether the CRF-containing projection from the amygdala to the BNST is involved in the mediation of stress-induced reinstatement of cocaine seeking by functionally interrupting the pathway.

METHODS

Rats trained to self-administer cocaine (1 mg/kg, IV, 9 days) were given extinction sessions after a 10- to 11-day drug-free period, followed by tests for stress-induced reinstatement (footshock: 15 min intermittent 0.8-mA footshocks given immediately before presentation of the previously active lever). Before the tests, animals were pretreated with either: (1) TTX (2.5 ng) in amygdala (including the CeA) in one hemisphere and D-Phe CRF(12-41) (50 ng) in BNST in the other, (2) unilateral TTX, or (3) unilateral D-Phe.

RESULTS

Footshock reinstated cocaine seeking following unilateral injections of either TTX in amygdala or D-Phe in BNST, but following the injection of both TTX in amygdala and D-Phe in BNST the effects of footshock were greatly attenuated.

CONCLUSION

These results suggest that the CRF-containing pathway from CeA to BNST is involved in mediating the effects of CRF and its receptor antagonist in the BNST on the reinstatement of cocaine seeking.

The role of dopamine in the nucleus accumbens in analgesia

Opioid and psychostimulant drugs have long been used for the relief of chronic pain in the clinical situation. Animal studies confirm that these drugs alleviate persistent or tonic pain. Little is known, however, about the neural systems underlying the suppression of tonic pain except that they are different from those mediating the suppression of phasic (i.e., sharp and short-lasting) pain. Although spinal and brainstem-descending pain suppression mechanisms play a role in mediating the inhibition of tonic pain, it appears that this response is additionally mediated by the activation of mechanisms lying rostral to the brainstem. Recent studies suggest that the activation of mesolimbic dopamine (DA) neurons, arising from the cell bodies of the ventral tegmental area (VTA) and projecting to the nucleus accumbens (NAcc), plays an important role in mediating the suppression of tonic pain. Other studies suggest that this pain-suppression system involving the activation of mesolimbic DA neurons is naturally triggered by exposure to stress, through the endogenous release of opioids and substance P (SP) in the midbrain.

CP-154,526, a selective, non-peptide antagonist of the corticotropin-releasing factor1 receptor attenuates stress-induced relapse to drug seeking in cocaine- and heroin-trained rats

We have found that peptide antagonists of corticotropin-releasing factor (CRF) receptors attenuate reinstatement of heroin and cocaine seeking induced by footshock. Here we examined the effect of a nonpeptide, selective CRF1 receptor antagonist, CP-154,526, on reinstatement of heroin and cocaine seeking induced by footshock. Rats were trained to self-administer heroin or cocaine (0.1 and 1.0 mg/kg per infusion, i.v., respectively) for 9-12 days. Extinction sessions were given for up to 14 days, during which saline was substituted for the drugs. Tests for reinstatement were then conducted after exposure to intermittent footshock (10 or 15 min, 0.5 mA). The footshock stressor reliably reinstated extinguished cocaine- and heroin-taking behavior. Pretreatment with CP-154,526 (15 and 30 mg/kg, s.c.) significantly attenuated the reinstatement effect of the stressor in both heroin- and cocaine-trained rats. CP-154,526, administered in the absence of the footshock stressor, did not affect extinguished drug seeking. In addition, in a separate experiment, CP-154,526 was shown not to alter high rates of lever pressing for a 10% sucrose solution, suggesting that the suppression of lever pressing in stress-induced reinstatement is not caused by a performance deficit. These results extend previous reports on the role of CRF in reinstatement of drug seeking induced by stressors. The present data also suggest that, to the extent that exposure to environmental stressors provoke relapse to drug use in humans, systemically effective CRF receptor antagonists may be of use in the treatment of relapse to drug use.

Alpha-2 adrenergic receptor agonists block stress-induced reinstatement of cocaine seeking

The alpha-2 adrenergic receptor agonists, clonidine, lofexidine and guanabenz, blocked stress- but not cocaine-induced reinstatement of cocaine seeking at doses that suppressed footshock-induced release of noradrenaline in prefrontal cortex and amygdala. Rats were trained to self-administer cocaine (0.5 mg/kg/infusion, i.v; 10-12 days) and, after a drug-free period (7-13 days), were returned to the self-administration chambers for daily extinction and reinstatement test sessions. Both intermittent footshock (15 min, 0.6 mA) and cocaine priming (20 mg/kg, i.p.) reinstated extinguished drug seeking. Pretreatment with either clonidine (20, or 40 microg/kg, i.p.) or lofexidine (50, 100, 150, or 200 microg/kg, i.p.) attenuated footshock- but not cocaine-induced reinstatement of cocaine seeking. Guanabenz (640 microg/kg, i.p.), an alpha-2 agonist with low affinity for imidazoline type-1 receptors, also attenuated footshock- but not cocaine-induced reinstatement of cocaine seeking. The results point to an important role for NE systems in the effects of footshock on relapse to cocaine seeking.

Spontaneous and induced cardiac arrhythmias in subendocardial Purkinje fibers surviving extensive myocardial infarction in dogs

The cellular electrophysiological mechanisms underlying the ventricular arrhythmias that accompany myocardial infarction were studied in isolated, superfused infarcted myocardium excised from dogs previously subjected to a two-stage ligation of the anterior descending coronary artery. Ventricular arrhythmias frequently occurred in the intact heart 24 hours after coronary occlusion. Surviving subendocardial Purkinje fibers in infarcts excised at this time were highly arrhythmic when they were studied with intracellular microelectrodes in vitro. These arrhythmias consisted of rapid, repetitive depolarizations and occurred spontaneously or could be induced by premature electrical stimulation. Premature stimulation also resulted in single unstimulated responses. In such instances, premature impulses conducted extremely slowly through the infarcted region where surviving Purkinje fiber action potential durations were extraordinarily prolonged. Conduction block at some sites in the infarct caused phenomena which were interpreted as reentrant beats. Some surviving subendocardial Purkinje fibers in the infarct demonstrated spontaneous diastolic depolarization and appeared to function as pacemakers in the absence of electrical stimulation. In some instances, these fibers constituted typical parasystolic foci, demonstrating both entrance and exit block. These results suggest that subendocardial Purkinje fibers which survive in an infarct may be the site of origin of some of the ventricular arrhythmias that accompany myocardial infarction.

High frequency of apolipoprotein E epsilon 2 allele in hemorrhage due to cerebral amyloid angiopathy

From the somewhat conflicting published data on apolipoprotein E (apoE) genotype in hemorrhage due to cerebral amyloid angiopathy (CAA), it is unclear whether apoE genotype influences the risk of CAA-related hemorrhage independently of its association with concomitant Alzheimer's disease (AD). We determined the apoE genotypes of 36 patients presenting with cerebral hemorrhage associated with histologically confirmed CAA. The frequency of apoE epsilon 2 was 0.25 and the frequency of apoE epsilon 4 was 0.18. Patients with CAA-related hemorrhage and concomitant AD pathology (CERAD criteria, n = 17) had a high apoE epsilon 4 frequency, close to that in AD cases without hemorrhage. Patients in whom CAA-related hemorrhage occurred in the absence of significant AD pathology (n = 13) had an apoE epsilon 4 frequency somewhat lower than non-AD controls without hemorrhage. However, in CAA-related hemorrhage, the apoE epsilon 2 frequency was high regardless of whether significant AD pathology was present. We conclude that whereas possession of apoE epsilon 2 may be a risk factor for cerebral hemorrhage due to CAA, apoE epsilon 4 is a risk factor for concomitant AD but not an independent risk factor for CAA-related hemorrhage.

Oral flecainide acetate for the treatment of ventricular arrhythmias

The antiarrhythmic efficacy and safety of oral flecainide acetate were assessed during a controlled, short-term dosage-maintenance study. Thirteen patients with chronic ventricular ectopy entered a placebo control period, and 11 with persistent, frequent (greater than 600 per 12 hours) premature ventricular complexes (PVCs) advanced to drug therapy. Of 10 patients completing a trial of different doses, nine responded completely, with a mean PVC suppression of 98,3 per cent. Repetitive PVCs were eliminated. The mean effective dose was 189 mg per 12 hours, and the effective plasma concentration before administration of a dose averaged 635 ng per milliliter. One patient responded partially (68 per cent of PVCs suppressed). Flecainide continued to be effective and well tolerated at the end of a two-week outpatient trial in the nine complete responders, maintaining an average PVC suppression of 94.6 per cent. The PR and QRS intervals were mildly prolonged. The echocardiographic ejection fraction was unchanged during treatment. The elimination half-life was long - 18.8 +/- 3.8 hours. Flecainide thus appears to be a highly effective and well-tolerated antiarrhythmic agent with favorable pharmacokinetics.

Alterations in dendritic morphology of prefrontal cortical and nucleus accumbens neurons in post-pubertal rats after neonatal excitotoxic lesions of the ventral hippocampus

Neonatal ventral hippocampal (nVH) lesions in rats result in adult onset of a number of behavioral and cognitive abnormalities analogous to those seen in schizophrenia, including hyperresponsiveness to stress and psychostimulants and deficits in working memory, sensorimotor gating and social interaction. Molecular and neurochemical alterations in the prefrontal cortex (PFC) and nucleus accumbens (NAcc) of nVH-lesioned animals suggest developmental reorganization of these structures following neonatal lesions. To determine whether nVH lesions lead to neuronal morphological changes, we investigated the effect of nVH lesion on dendritic structure and spine density of pyramidal neurons of the PFC and medium spiny neurons of the NAcc. Bilateral ibotenic acid-induced lesion of the VH was made in Sprague-Dawley pups at postnatal day 7 (P7); and at P70, neuronal morphology was quantified by modified Golgi-Cox staining. The results show that length of basilar dendrites and branching and the density of dendritic spines on layer 3 pyramidal neurons were significantly decreased in rats with nVH lesions. Medium spiny neurons from the NAcc showed a decrease in the density of dendritic spines without significant changes in dendritic length or arborization. The data, comparable to those observed in the PFC of schizophrenic patients, suggest that developmental loss of excitatory projections from the VH may lead to altered neuronal plasticity in the PFC and the NAcc that may contribute to the behavioral changes in these animals.