Giorgio Racagni

Early maternal deprivation reduces the expression of BDNF and NMDA receptor subunits in rat hippocampus

It is well accepted that events that interfere with the normal program of neuronal differentiation and brain maturation may be relevant for the etiology of psychiatric disorders, setting the stage for synaptic disorganization that becomes functional later in life. In order to investigate molecular determinants for these events, we examined the modulation of the neurotrophin brain-derived neurotrophic factor (BDNF) and the glutamate NMDA receptor following 24 h maternal separation (MD) on postnatal day 9. We found that in adulthood the expression of BDNF as well as of NR-2A and NR-2B, two NMDA receptor forming subunits, were significantly reduced in the hippocampus of MD rats whereas, among other structures, a slight reduction of NR-2A and 2B was detected only in prefrontal cortex. These changes were not observed acutely, nor in pre-weaning animals. Furthermore we found that in MD rats the modulation of hippocampal BDNF in response to an acute stress was altered, indicating a persistent functional impairment in its regulation, which may subserve a specific role for coping with challenging situations. We propose that adverse events taking place during brain maturation can modulate the expression of molecular players of cellular plasticity within selected brain regions, thus contributing to permanent alterations in brain function, which might ultimately lead to an increased vulnerability for psychiatric diseases.

Guidelines for depot antipsychotic treatment in schizophrenia

These guidelines for depot antipsychotic treatment in schizophrenia were developed during a two-day consensus conference held on July 29 and 30, 1995 in Siena, Italy. Depot antipsychotic medications were developed in the 1960s as an attempt to improve the long-term treatment of schizophrenia (and potentially other disorders benefiting from long-term antipsychotic medication). Depot drugs as distinguishable from shorter acting intramuscularly administered agents can provide a therapeutic concentration of at least a seven day duration in one parenteral dose. The prevention of relapse in schizophrenia remains an enormous public health challenge worldwide and improvements in this area can have tremendous impact on morbidity, mortality and quality of life, as well as direct and indirect health care costs. Though there has been debate as to what extent depot (long-acting injectable) antipsychotics are associated with significantly fewer relapses and rehospitalizations, in our view when all of the data from individual trials and metaanalyses are taken together, the findings are extremely compelling in favor of depot drugs. However in many countries throughout the world fewer than 20% of individuals with schizophrenia receive these medications. The major advantage of depot antipsychotics over oral medication is facilitation of compliance in medication taking. Non-compliance is very common among patients with schizophrenia and is a frequent cause of relapse. In terms of adverse effects, there are not convincing data that depot drugs are associated with a significantly higher incidence of adverse effects than oral drugs. Therefore in our opinion any patient for whom long-term antipsychotic treatment is indicated should be considered for depot drugs. In choosing which drug the clinician should consider previous experience, personal patient preference, patients history of response (both therapeutic and adverse effects) and pharmacokinetic properties. In conclusion the use of depot antipsychotics has important advantages in facilitating relapse prevention. Certainly pharmacotherapy must be combined with other treatment modalities as needed, but the consistent administration of the former is often what enables the latter.

Treatment resistant depression: methodological overview and operational criteria

A wide variety of definitions are used for Treatment Resistant Depression (TRD), considering various criteria and different concepts. Some of the key issues are: the diagnosis, the treatment adequacy in terms of dose and duration, the treatment response assessment and the number of failed therapeutic trials required. Systematic research has been characterizing the concept and criteria to define the different variables involved. Lack of consensus on these issues limits comparison across clinical trials and interpretation of treatment efficacy in the management of treatment resistant patients. Through reanalyzes of available data, we point out the limits of TRD definitions and propose conceptual and operational criteria for a collaborative research project on TRD. It appears that a number of variables commonly associated to treatment resistance are independent of patients characteristics and mainly refer to misdiagnosis and inadequate treatment. The proposed criteria are intended for therapeutic trials in TRD, combining the evaluation of treatment efficiency and the validation of the concept of TRD itself. Major depression with poor response to two adequate trials of different classes of antidepressants is proposed for an operational definition of TRD. Rationale for this definition is discussed in contrast to alternative definitions.

Postnatal repeated maternal deprivation produces age-dependent changes of brain-derived neurotrophic factor expression in selected rat brain regions

BACKGROUND Adverse life events occurring early in development may alter the correct program of brain maturation and render the organism more vulnerable to psychiatric disorders. Identification of persistent changes associated with these events is crucial for the development of novel therapeutic strategies. METHODS We used postnatal repeated maternal deprivation (MD) from postnatal day (PND) 2-14 to investigate changes in brain-derived neurotrophic factor (BDNF) levels. RNase protection assay and enzyme linked immunosorbent assay were employed to determine the anatomic profile of neurotrophin expression at different ages following MD. RESULTS We found that MD produces a short-term up-regulation of neurotrophin expression in hippocampus and prefrontal cortex, as measured on PND 17, whereas at adulthood, a selective reduction of BDNF expression was observed in prefrontal cortex. When adult animals were challenged with a chronic swim stress paradigm, both a reduced expression of BDNF in prefrontal cortex and a significant reduction in striatal protein levels were found only in control subjects, whereas levels in the MD group were not further decreased. CONCLUSIONS Our data suggest that MD produces a significant reduction of BDNF expression within prefrontal cortex and striatum, which may render these structures less plastic and more vulnerable under challenging conditions.

Neuronal plasticity: a link between stress and mood disorders.

Although stress represents the major environmental element of susceptibility for mood disorders, the relationship between stress and disease remains to be fully established. In the present article we review the evidence in support for a role of neuronal plasticity, and in particular of neurotrophic factors. Even though decreased levels of norepinephrine and serotonin may underlie depressive symptoms, compelling evidence now suggests that mood disorders are characterized by reduced neuronal plasticity, which can be brought about by exposure to stress at different stages of life. Indeed the expression of neurotrophic molecules, such as the neurotrophin BDNF, is reduced in depressed subjects as well as in experimental animals exposed to adverse experience at early stages of life or at adulthood. These changes show an anatomical specificity and might be sustained by epigenetic mechanisms. Pharmacological intervention may normalize such defects and improve neuronal function through the modulation of the same factors that are defective in depression. Several studies have demonstrated that chronic, but not acute, antidepressant treatment increases the expression of BDNF and may enhance its localization at synaptic level. Antidepressant treatment can normalize deficits in neurotrophin expression produced by chronic stress paradigms, but may also alter the modulation of BDNF under acute stressful conditions. In summary, there is good agreement in considering neuronal plasticity, and the expression of key proteins such as the neurotrophin BDNF, as a central player for the effects of stress on brain function and its implication for psychopathology. Accordingly, effective treatments should not limit their effects to the control of neurotransmitter and hormonal dysfunctions, but should be able to normalize defective mechanisms that sustain the impairment of neuronal plasticity.

Nicotine prevents experimental Parkinsonism in rodents and induces striatal increase of neurotrophic factors

Abstract: The repeated finding of an apparent protective effect of cigarette smoking on the risk of Parkinsons disease is one of the few consistent results in the epidemiology of this disorder. Among the numerous substances that originate from tobacco smoke, nicotine is by far the most widely studied. Nicotine is a natural alkaloid that has considerable stimulatory effects on the CNS. Its effects on the CNS are mediated by the activation of neuronal heteromeric acetylcholine‐gated ion channel receptors (nAChRs, also termed nicotinic acetylcholine receptors). In the present study, we describe the neuroprotective effects of (−)‐nicotine in two animal models of parkinsonism: diethyldithiocarbamate‐induced enhancement of 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine toxicity in mice and methamphetamine‐induced neurotoxicity in rats and mice. The neuroprotective effect of (−)‐nicotine was very similar to that of the noncompetitive NMDA receptor antagonist (+)‐MK‐801. In parallel experiments, we found that (−)‐nicotine induces the basic fibroblast growth factor‐2 (FGF‐2) and the brain‐derived neurotrophic factor in rat striatum. The effect of (−)‐nicotine on the induction of FGF‐2 was prevented by the nAChR antagonist mecamylamine. We also found that (+)‐MK‐801 was able to induce FGF‐2 in the striatum. As trophic factors have been reported to be neuroprotective for dopaminergic cells, our data suggest that the increase in neurotrophic factors is a possible mechanism by which (−)‐nicotine protects from experimental parkinsonisms.

Chronic Antidepressants Reduce Depolarization-Evoked Glutamate Release and Protein Interactions Favoring Formation of SNARE Complex in Hippocampus

Glutamate neurotransmission was recently implicated in the action of stress and in antidepressant mechanisms. We report that chronic (not acute) treatment with three antidepressants with different primary mechanisms (fluoxetine, reboxetine, and desipramine) markedly reduced depolarization-evoked release of glutamate, stimulated by 15 or 25 mm KCl, but not release of GABA. Endogenous glutamate and GABA release was measured in superfused synaptosomes, freshly prepared from hippocampus of drug-treated rats. Interestingly, treatment with the three drugs only barely changed the release of glutamate (and of GABA) induced by ionomycin. In synaptic membranes of chronically treated rats we found a marked reduction in the protein-protein interaction between syntaxin 1 and Thr286-phosphorylated αCaM kinase II (α-calcium/calmodulin-dependent protein kinase II) (an interaction previously proposed to promote neurotransmitter release) and a marked increase in the interaction between syntaxin 1 and Munc-18 (an interaction proposed to reduce neurotransmitter release). Furthermore, we found a selective reduction in the expression level of the three proteins forming the core SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complex. These findings suggest that antidepressants work by stabilizing glutamate neurotransmission in the hippocampus and that they may represent a useful tool for the study of relationship between functional and molecular processes in nerve terminals.

High Sensitivity of Glutamate Uptake to Extracellular Free Arachidonic Acid Levels in Rat Cortical Synaptosomes and Astrocytes

Abstract: By using both synaptosomes and cultured astrocytes from rat cerebral cortex, we have investigated the inhibitory action of arachidonic acid on the high‐affinity glutamate uptake systems, focusing on the possible physiological significance of this mechanism. Application of arachidonic acid (1–100 μM) to either preparation leads to fast (within 30 s) and largely reversible reduction in the uptake rate. When either melittin (0.2–1 mg/ml), a phospholipase A2 activator, or thimerosal (50–200 μM), which inhibits fatty acid reacylation in phospholipids, is applied to astrocytes, both an enhancement in extracellular free arachidonate and a reduction in glutamate uptake are seen. The two effects display similar dose dependency and time course. In particular, 10% uptake inhibition correlates with 30% elevation in free arachidonate. whereas inhibition ≥60% is paralleled by threefold stimulation of arachidonate release. In the presence of albumin (1–10 mg/ml), a free fatty acid‐binding protein, inhibition by either melittin, thimerosal, or arachidonic acid is prevented and an enhancement of glutamate uptake above the control levels is observed. Our data show that neuronal and glial glutamate transport systems are highly sensitive to changes in extracellular free arachidonate levels and suggest that uptake inhibition may be a relevant mechanism in the action of arachidonic acid at glutamatergic synapses.

Acute Stress Increases Depolarization-Evoked Glutamate Release in the Rat Prefrontal/Frontal Cortex: The Dampening Action of Antidepressants

Background Behavioral stress is recognized as a main risk factor for neuropsychiatric diseases. Converging evidence suggested that acute stress is associated with increase of excitatory transmission in certain forebrain areas. Aim of this work was to investigate the mechanism whereby acute stress increases glutamate release, and if therapeutic drugs prevent the effect of stress on glutamate release. Methodology/Findings Rats were chronically treated with vehicle or drugs employed for therapy of mood/anxiety disorders (fluoxetine, desipramine, venlafaxine, agomelatine) and then subjected to unpredictable footshock stress. Acute stress induced marked increase in depolarization-evoked release of glutamate from synaptosomes of prefrontal/frontal cortex in superfusion, and the chronic drug treatments prevented the increase of glutamate release. Stress induced rapid increase in the circulating levels of corticosterone in all rats (both vehicle- and drug-treated), and glutamate release increase was blocked by previous administration of selective antagonist of glucocorticoid receptor (RU 486). On the molecular level, stress induced accumulation of presynaptic SNARE complexes in synaptic membranes (both in vehicle- and drug-treated rats). Patch-clamp recordings of pyramidal neurons in the prefrontal cortex revealed that stress increased glutamatergic transmission through both pre- and postsynaptic mechanisms, and that antidepressants may normalize it by reducing release probability. Conclusions/Significance Acute footshock stress up-regulated depolarization-evoked release of glutamate from synaptosomes of prefrontal/frontal cortex. Stress-induced increase of glutamate release was dependent on stimulation of glucocorticoid receptor by corticosterone. Because all drugs employed did not block either elevation of corticosterone or accumulation of SNARE complexes, the dampening action of the drugs on glutamate release must be downstream of these processes. This novel effect of antidepressants on the response to stress, shown here for the first time, could be related to the therapeutic action of these drugs.

Posttraumatic Stress Disorder: Diagnosis and Epidemiology, Comorbidity and Social Consequences, Biology and Treatment

Epidemiological studies clearly indicate that posttraumatic stress disorder (PTSD) is becoming a major health concern worldwide even if still poorly recognized and not well treated. PTSD commonly co-occurs with other psychiatric disorders, and several symptoms overlap with major depressive disorders, anxiety disorders and substance abuse; this may contribute to diagnostic confusion and underdiagnosis. This anxiety disorder provokes significant occupational, psychiatric, medical and psychosocial disability, and its consequences are enormously costly, not only to the survivors and their families, but also to the health care system and society. Work impairment associated with PTSD is very similar to the amount of work impairment associated with major depression. The pathophysiology of PTSD is multifactorial and involves dysregulation of the serotonergic as well as the noradrenergic system. A rational therapeutic approach should normalize the specific psychobiological alterations associated with PTSD. This can be achieved through the use of antidepressant drugs, mainly of those that potentiate serotonergic mechanisms. Recent double-blind placebo-controlled studies report the efficacy of selective serotonin reuptake inhibitors. Several cognitive-behavioral and psychosocial treatments have also been reported to be efficacious and could be considered when treating PTSD patients.