The biological basis of anxiety. An overview

Prolonged exposure of rats to varenicline increases anxiety and alters serotonergic system, but has no effect on memory

Varenicline is a drug used for smoking addiction cessation treatment and acts as a partial agonist of nicotinic cholinergic receptors. Recent clinical trial data support use of varenicline for treatment of conditions/addictions that are not related to smoking cessation. Considering the importance of this issue and the need for new studies on its effects, especially on behavior, more studies using animal models are necessary. Thus, the aim of this study was to evaluate the effects of prolonged exposure to varenicline in anxiety-like behavior and memory, as well as in cerebral neurochemistry of rats. Male rats received three different doses of varenicline: 0.03 (therapeutic dose for humans), 0.1 and 0.3 mg/kg orally (gavage) for 30 days. Animal behavior was analyzed through open field, elevated plus maze, light/dark box, social interaction, Barnes maze and novel object recognition tests. Neurotransmitter levels and their metabolites in different brain structures (hippocampus, striatum and frontal cortex) were measured. Results showed that prolonged exposure of rats to varenicline: 1) did not interfere in motor activity, but caused an anxiogenic effect on elevated plus maze, light/dark box and social interaction testes; 2) did not alter memory; and 3) promoted alterations on serotoninergic system in the striatum and frontal cortex. In conclusion, compilation of the data indicates that prolonged exposure of rats to varenicline promoted anxiogenic effects and alteration in serotonergic system, which corroborated behavioral findings.

Individually ventilated cages cause chronic low-grade hypoxia impacting mice hematologically and behaviorally

Use of individually ventilated caging (IVC) systems for mouse-based laboratory investigation has dramatically increased. We found that without mice present, intra-cage oxygen concentration was comparable (21%) between IVC housing and ambient environment caging (AEC) that used wire top lids. However, when mice were housed 4-to-a-cage for 1week, intra-cage oxygen dropped to 20.5% in IVC housing as compared to 21% for AEC housing. IVC intra-cage humidity was also elevated relative to AEC housing. Mice raised in IVC housing as compared to mice raised in AEC housing had higher RBC mass, hematocrit and hemoglobin concentrations. They also had elevated platelet counts but lower white blood cell counts. IVC mice, relative to AEC mice, had increased saccharin preference and increased fluid consumption but similar locomotion, food intake, social exploration and novel object recognition when tested in an AEC environment. Taken together, these data indicate that ventilated caging systems can have a 0.5% reduction from ambient oxygen concentration that is coupled to mouse red blood cell indices indicative of chronic exposure to a hypoxia. Importantly, IVC housing can impact behavioral testing for depressive-like behavior.

Analgesia and local anesthesia during invasive procedures in the neonate

BACKGROUND

Preterm and full-term neonates admitted to the neonatal intensive care unit or elsewhere in the hospital are routinely subjected to invasive procedures that can cause acute pain. Despite published data on the complex behavioral, physiologic, and biochemical responses of these neonates and the detrimental short- and long-term clinical outcomes of exposure to repetitive pain, clinical use of pain-control measures in neonates undergoing invasive procedures remains sporadic and suboptimal. As part of the Newborn Drug Development Initiative, the US Food and Drug Administration and the National Institute of Child Health and Human Development invited a group of international experts to form the Neonatal Pain Control Group to review the therapeutic options for pain management associated with the most commonly performed invasive procedures in neonates and to identify research priorities in this area.

OBJECTIVE

The goal of this article was to review and synthesize the published clinical evidence for the management of pain caused by invasive procedures in preterm and full-term neonates.

METHODS

Clinical studies examining various therapies for procedural pain in neonates were identified by searches of MEDLINE (1980-2004), the Cochrane Controlled Trials Register (The Cochrane Library, Issue 1, 2004), the reference lists of review articles, and personal files. The search terms included specific drug names, infant-newborn, infant-preterm, and pain, using the explode function for each key word. The English-language literature was reviewed, and case reports and small case series were discarded.

RESULTS

The most commonly performed invasive procedures in neonates included heel lancing, venipuncture, IV or arterial cannulation, chest tube placement, tracheal intubation or suctioning, lumbar puncture, circumcision, and SC or IM injection. Various drug classes were examined critically, including opioid analgesics, sedative/hypnotic drugs, nonsteroidal anti-inflammatory drugs and acetaminophen, injectable and topical local anesthetics, and sucrose. Research considerations related to each drug category were identified, potential obstacles to the systematic study of these drugs were discussed, and current gaps in knowledge were enumerated to define future research needs. Discussions relating to the optimal design for and ethical constraints on the study of neonatal pain will be published separately. Well-designed clinical trials investigating currently available and new therapies for acute pain in neonates will provide the scientific framework for effective pain management in neonates undergoing invasive procedures.

Platelet paroxetine binding in post-traumatic stress disorder

Sixty-two subjects, 45 with post-traumatic stress disorder (PTSD) and 17 healthy control subjects, were examined in a study of serotonin function measured by [3H]paroxetine binding to platelet membranes. Subjects were selected from male combat exposed veterans. The mean (+/- S.D.) Kd was 0.078 +/- 0.045 nM for the PTSD patient group and 0.064 +/- 0.037 nM for the control group. The mean Bmax was 934 + 238 fmol/mg protein for the PTSD patient group and 1011 +/- 363 fmol/mg protein for the control group. There was no significant difference between the groups for either Kd or Bmax before or after controlling for season of sampling. There were no significant differences between subjects with current PTSD and those with PTSD in the past, or between PTSD subjects with or without concurrent major depressive disorder. This study finds no relationship between PTSD, major depressive disorder and peripheral serotonin function measured by [3H]paroxetine binding to blood platelets.

Baseline and fear-potentiated startle in panic disorder patients

The present study investigated whether patients with panic disorder had an increase in the startle response and whether this effect, if present, was specific to anticipatory anxiety. The eyeblink component of the acoustic startle reflex was measured in a paradigm involving the anticipation of electric shocks (fear-potentiated startle) in 34 patients with panic disorder and 49 healthy controls. Startle was also recorded in the absence of specific threat at the beginning and at the end of the testing. The testing consisted of three phases: adaptation, fear-potentiated startle, and recovery. In the adaptation and recovery phases, startle stimuli were delivered in the absence of threat. In the fear-potentiated startle phase, startle stimuli were delivered in threat conditions, when subjects anticipated shocks, and in safe conditions that predicted the absence of shocks. Startle was larger in the younger patients (age < 40 years old) compared to the younger controls throughout the testing. The difference reached significance only during the fear-potentiated startle phase, however. Startle was nonsignificantly reduced in the older patients (age > or = 39 years old), compared to the older controls. The results are discussed in terms of the contextual effects of the experimental setting.

Serotonergic function in panic disorder: endocrine responses to D-fenfluramine

1. Prolactin and cortisol responses to d-fenfluramine were measured in 16 patients with DSM-III-R panic disorder and 14 normal controls. 2. Patients showed a greater mean prolactin response than controls but the difference between groups was not statistically significant (P > 0.05, MANOVA). 3. No consistent differences were observed between patients and controls with respect to cortisol responses (P > 0.05, MANOVA). 4. The results do not support the hypothesis of hypersensitive post-synaptic serotonin receptors in patients with panic disorder. 5. Studies in larger groups are necessary to confirm the trend and to explore receptor subtype sensitivity.

Psychopathology of pancreatic cancer. A psychobiologic probe

Reports of characteristic psychiatric symptoms occurring in patients with pancreatic cancer appear regularly in the literature. A review of this literature reveals that symptoms of depression and/or anxiety may appear in approximately 50% of patients with pancreatic cancer before the diagnosis is made. This review proposes that the psychopathology of pancreatic tumors may be linked to tumor-induced changes in neuroendocrine or acid-base systems. Although confirmatory data are lacking, informed speculation centers on the potential role of adrenocorticotropic hormone, parathyroid hormone, thyrotropin-releasing hormone, glucagon, serotonin, insulin, and bicarbonate in the production of depression and/or anxiety in this disease. Elucidation of the pathophysiology of the psychiatric symptoms in patients with pancreatic cancer may provide a marker for early diagnosis of pancreatic neoplasia as well as a probe into the biologic bases of depression and anxiety.

Intravenous sodium lactate decreases plasma GABA levels in man

Gamma aminobutyric acid (GABA), an inhibitory neurotransmitter, may play an important role in anxiety. We studied changes in plasma GABA levels in nine healthy subjects before and after infusions of sodium lactate and dextrose. Plasma GABA significantly decreased during infusions of sodium lactate (109.3 +/- 4.4 versus 91.6 +/- 5.1 pmol/ml; P = 0.0001) but not during infusions of dextrose.

Diazepam (Valium): its dependency liability

Reports of the withdrawal syndrome following discontinuation of diazepam and drug dependence fears have contributed to diazepam's displacement as the most popular anxiolytic agent. Reports of the withdrawal syndrome, the factors involved in withdrawal, and the remedies proposed for diazepam withdrawal symptoms are reviewed.

Fenfluramine provocation of anxiety in patients with panic disorder

Fenfluramine, and indirect serotonergic agonist, was administered to nine women with panic disorder, nine women with major depressive disorder, and nine women controls. Panic disorder patients revealed significantly greater anxiogenic responses to fenfluramine administration at all 5 hourly measurement points than either depressed patients or control subjects. Prolactin and cortisol responses to fenfluramine were also significantly greater in panic disorder patients than in either depressed patients or control subjects. Placebo administration did not elicit robust or significantly different anxiety or hormonal responses in panic disorder patients or control subjects. These data offer evidence that serotonergic hyperresponsivity must be considered as an important factor in the mechanism of events provoking overt panic attacks.

Systemic hormonal and physiological abnormalities in anxiety disorders

Among the studies of systemic hormonal and physiological abnormalities associated with anxiety disorders, the most consistent and extensive findings suggest (a) peripheral adrenergic hyperactivity (including increases in norepinephrine but not epinephrine) and functional dysregulation, (b) increased incidence of mitral valve prolapse in panic patients, and (c) normal suppressibility of the hypothalamic-pituitary-adrenal cortical endocrine system with dexamethasone in panic patients. Other less-certain findings include (a) increased circulating concentrations of plasma ACTH and/or cortisol, and prolactin, in panic patients, (b) increased platelet monoamine oxidase activity in generalized anxiety and/or panic patients, (c) decreased gonadal axis activity in some anxious individuals, (d) decreased nighttime melatonin plasma concentrations in panic patients, and (e) peripheral alpha 2 and beta-adrenoreceptor down-regulation, with normal serotonin binding parameters. These findings, taken together, provide tentative support for dysfunction in adrenergic and GABAergic central nervous system mechanisms in people with anxiety disorders. Abnormal anxiety and normal stress both show evidence of adrenergic hyperactivity; however, there appear to be differences in hormonal profiles, especially the apparent lack of increase of epinephrine during panic attacks, as well as differences in the reactivity of the system, and in the "trigger" mechanisms which determine when the response occurs.

Neuropsychophysiological correlates of lactate-induced panic

1. One of the simplest and most direct applications of neuropsychophysiological techniques is to anxiety disorders. 2. The physiological changes accompanying the lactate induction of panic appear, for most response systems, to be similar to those found spontaneously in anxious patients and are characteristic of a state of hyperarousal. 3. Patients vulnerable to lactate-induced panic exhibit higher than normal pre-panic autonomic activity, elevated autonomic-somatic activity during lactate-induced panic and an EEG response to provoked panic which appears to be comprised of a "paradoxical" shift towards slow wave delta activity and an altered brainstem evoked response. 4. Additional studies are warranted to determine the relationship of these physiological changes to the triggering of panic and preliminary attempts in this direction are discussed.

Panic disorder: evidence for genetic vulnerability

Many studies have suggested that a genetic predisposition to the development of panic disorder exists. These studies are examined and their limitations discussed. It is suggested that only by the analysis of comprehensive family and twin data, coupled with other measures such as the search for possible single gene association or linkage and study of the children of panic disorder patients, will the mechanism for the 'familiarity' noted in panic disorder patients be elucidated. Delineation of the mode of transmission of panic disorder may allow preventative intervention with those at risk before they develop panic.

Platelet serotonin levels in panic disorder

Platelet serotonin levels were examined in 18 patients with panic disorder and compared to platelet serotonin levels of eight healthy controls. There was no statistically significant difference in the platelet serotonin levels between the two groups.