Papers by Hendrikus Hendriksen
European Journal of Pharmacology, 2015
First line antidepressants are the so-called SSRIs (selective serotonin reuptake inhibitors), e.g... more First line antidepressants are the so-called SSRIs (selective serotonin reuptake inhibitors), e.g. fluvoxamine, fluoxetine, sertraline, paroxetine and escitalopram. Unfortunately, these drugs mostly do not provide full symptom relief and have a slow onset of action. Therefore other antidepressants are also being prescribed that inhibit the reuptake of norepinephrine (e.g. reboxetine, desipramine) or the reuptake of both serotonin (5-HT) and norepinephrine (e.g. venlafaxine, duloxetine, milnacipran). Nevertheless, many patients encounter residual symptoms such as impaired pleasure, impaired motivation, and lack of energy. It is hypothesized that an impaired brain reward system may underlie these residual symptoms. In agreement, there is some evidence that reuptake inhibitors of both norepinephrine and dopamine (e.g. methylphenidate, bupropion, nomifensine) affect these residual symptoms. In the pipeline are new drugs that block all three monoamine transporters for the reuptake of 5-HT, norepinephrine and dopamine, the so-called triple reuptake inhibitors (TRI). The working mechanisms of the above-mentioned antidepressants are discussed, and it is speculated whether depressed patients with different symptoms, sometimes even opposite ones due to atypical or melancholic features, can be matched with the different drug treatments available. In other words, is personalized medicine for major depression an option in the near future?
European Journal of Pharmacology, 2014
We used the inescapable foot shock paradigm (IFS) in rats as an animal model for post-traumatic s... more We used the inescapable foot shock paradigm (IFS) in rats as an animal model for post-traumatic stress disorder (PTSD). Previously we showed that exercise reversed the enhanced stress sensitivity induced by IFS. From literature it is known that food restriction has antidepressant and anxiolytic effects. Since both treatments influence energy expenditure, we questioned whether food restriction reduces anxiety in the IFS model via a comparable, NPY dependent mechanism as enrichment.
European Journal of Pharmacology, 2014
Olfactory bulbectomy (OBX), the surgical removal of the olfactory bulbs, lead, both in mice and r... more Olfactory bulbectomy (OBX), the surgical removal of the olfactory bulbs, lead, both in mice and rats, to a specific set of behavioral changes in social behavior, cognitive function and activity. The latter is often used as a readout measure to predict antidepressant effects of new compounds. More recently, the model is used to study neurodegeneration and the associated cognitive decline. Although most of the OBX-induced behavioral and neurochemical changes seen in mice and rats are very similar, there are also some remarkable differences. For instance, OBX has different effects on BDNF and the 5-HT 2c receptor of these two species. These species differ also in how they respond to certain treatments after OBX. In this review we describe these species-specific differences and discuss what they may mean in terms of translational value.
PLoS ONE, 2010
Background: Post traumatic stress disorder (PTSD) can be considered the result of a failure to re... more Background: Post traumatic stress disorder (PTSD) can be considered the result of a failure to recover after a traumatic experience. Here we studied possible protective and therapeutic aspects of environmental enrichment (with and without a running wheel) in Sprague Dawley rats exposed to an inescapable foot shock procedure (IFS).
Psychopharmacology, 2011
Rationale Olfactory bulbectomy (OBX) in a laboratory rodent leads to numerous behavioral deficits... more Rationale Olfactory bulbectomy (OBX) in a laboratory rodent leads to numerous behavioral deficits and involves cognitive and motor changes that are used to model major depression, but may also be a valuable tool in the study of neurodegenerative disorders like Alzheimer's disease. Objectives This experiment evaluated the effects of simvastatin, a cholesterol-lowering drug with putative neuroprotective properties, on OBX-induced behavioral changes.
Psychopharmacology, 2012
Rationale Repeated activation of corticotropin-releasing factor (CRF) receptors is associated wit... more Rationale Repeated activation of corticotropin-releasing factor (CRF) receptors is associated with increased anxiety and enhanced stress responsivity, which may be mediated via limbic GABAergic and glutamatergic transmission. Objective The present study investigated molecular and functional alterations in GABA A receptor (GABA A R) and metabotropic glutamate receptor (mGluR) responsivity in transgenic mice that chronically overexpress CRF. Methods CRF 1 receptor, GABA A R, and mGluR sensitivity were determined in CRF-overexpressing mice using the stress-induced hyperthermia (SIH) test. In addition, we measured mRNA expression levels of GABA A R α subunits and mGluRs in the amygdala and hypothalamus.
Neuropharmacology, 2012
Exposure-based cognitive behavioral therapy in post-traumatic stress disorder (PTSD) patients rel... more Exposure-based cognitive behavioral therapy in post-traumatic stress disorder (PTSD) patients relieves symptoms caused by fear association as well as symptoms that are not the result of associative learning. We used the inescapable foot shock model (IFS), an animal model for PTSD, to study the possible involvement of glutamate receptors, the corticotropin-releasing factor (CRF) system, and the neuropeptide Y (NPY) system in the reduction of stress sensitization following repeated re-exposure to the conditioning context. Starting one week after the IFS procedure, the rats were repeatedly re-exposed to the shock environment. Stress sensitivity was measured in a modified open field test (sudden silence was used as a stressor). Selected mRNAs (GluN1, -2A-C, GluA1-4, GluK1-5, CRF, CRF-R1, NPY, NPY-Y1) were quantified in the amygdala.
Neuropharmacology, 2012
Depression, especially in the elderly, is associated with poor cognitive functioning. Exercise ha... more Depression, especially in the elderly, is associated with poor cognitive functioning. Exercise has received much attention in the treatment for depression and also dementia. Here we studied the effect of an enriched environment combined with voluntary exercise (EE/VE) on the olfactory bulbectomized (OBX) rat. The OBX rat is hyperactive in an open field, which is normalized by chronic antidepressant treatment, and suffers from learning and memory impairments. Neurotrophic factors are thought to be involved in the antidepressant action of EE/VE. Hyperactivity and cognitive functioning (both hippocampal dependent and independent tasks) were investigated before and after EE/VE. We quantified hippocampal mRNA levels of the neurotrophic factors BDNF, VGF and VEGF. VEGF receptor (FLK-1) inhibition was achieved by i.c.v administration of the antagonist SU5416 during the period of EE/VE. OBX almost completely blocked fear memory acquired either 48 h or 28 days before surgery. EE/EV normalized OBX-induced hyperactivity in open field, while having no effect on the decrease in hippocampal dependent learning and memory. VEGF mRNA levels in hippocampus were significantly increased both in OBX and control rats following EE/VE. OBX reduced BDNF mRNA levels, but EE did not reverse this. Inhibition of the FLK-1 receptor did not suppress EE/VE induced normalization of the hyperactivity of the OBX rat.
European Journal of Pharmacology, 2014
The development of new pharmacological therapies starts with target discovery. Finding new therap... more The development of new pharmacological therapies starts with target discovery. Finding new therapeutic targets for anxiety disorders is a difficult process. Most of the currently described drugs for post-traumatic stress disorder (PTSD) are based on the inhibition of serotonin reuptake. The mechanism of action of selective serotonin reuptake inhibitors was already described in 1977 . Now, almost 40 years later, we still rely on the same mechanism of action and more effective pharmacological therapies, based on other working mechanisms, are not on the market yet. Finding new molecular switches that upon modulation cure or alleviate the disorder is hampered by a lack of valid animal models. Many of the characteristics of psychiatric disorders are typically human and hence animal models feature only part of the underlying pathology. In this review we define a set of criteria for animal models of PTSD. First, we describe the symptomatology and pathology of PTSD and the current pharmacological and non-pharmacological treatment options. Next, we compare three often-used animal models and analyze how these models comply with the set of criteria. Finally, we discuss how resolving the underlying mechanisms of effective non-pharmacological treatments (environmental enrichment, re-exposure) may aid therapeutic target discovery.
Neuropharmacology, 2014
Rising neurodegenerative and depressive disease prevalence combined with the lack of effective ph... more Rising neurodegenerative and depressive disease prevalence combined with the lack of effective pharmaceutical treatments and dangerous side effects, has created an urgent need for the development of effective therapies. Considering that these disorders are multifactorial in origin, treatments designed to interfere at different mechanistic levels may be more effective than the traditional single-targeted pharmacological concepts. To that end, an experimental diet composed of zinc, melatonin, curcumin, piperine, eicosapentaenoic acid (EPA, 20:5, n-3), docosahexaenoic acid (DHA, 22:6, n-3), uridine, and choline was formulated. This diet was tested on the olfactory bulbectomized rat (OBX), an established animal model of depression and cognitive decline. The ingredients of the diet have been individually shown to attenuate glutamate excitoxicity, exert potent anti-oxidant/anti-inflammatory properties, and improve synaptogenesis; processes that all have been implicated in neurodegenerative diseases and in the cognitive deficits following OBX in rodents. Dietary treatment started 2 weeks before OBX surgery, continuing for 6 weeks in total. The diet attenuated OBX-induced cognitive and behavioral deficits, except long-term spatial memory. Ameliorating effects of the diet extended to the control animals. Furthermore, the experimental diet reduced hippocampal atrophy and decreased the peripheral immune activation in the OBX rats. The ameliorating effects of the diet on the OBX-induced changes were comparable to those of the NMDA receptor antagonist, memantine, a drug used for the management of Alzheimer's disease. This proof-of-concept study suggests that a diet, which simultaneously targets multiple disease etiologies, can prevent/impede the development of a neurodegenerative and depressive disorders and the concomitant cognitive deficits.
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Papers by Hendrikus Hendriksen