Acquisition and reversal of taste/tactile discrimination after forebrain noradrenaline depletion

Unplanned intensive care unit readmission after surgical treatment in patients with newly diagnosed glioblastoma - forfeiture of surgically achieved advantages?

Postoperative intensive care unit (ICU) monitoring is an established option to ensure patient safety after resection of newly diagnosed glioblastoma. In contrast, secondary unplanned ICU readmission following complicating events during the initial postoperative course might be associated with severe morbidity and impair initially intended surgical benefit. In the present study, we assessed the prognostic impact of secondary ICU readmission and aimed to identify preoperatively ascertainable risk factors for the development of such adverse events in patients treated surgically for newly diagnosed glioblastoma. Between 2013 and 2018, 240 patients were surgically treated for newly diagnosed glioblastoma at the authors' neuro-oncological center. Secondary ICU readmission was defined as any unplanned admission to the ICU during initial hospital stay. A multivariable logistic regression analysis was performed to identify preoperatively measurable risk factors for unplanned ICU readmission. Nineteen of 240 glioblastoma patients (8%) were readmitted to the ICU. Median overall survival of patients with unplanned ICU readmission was 9 months compared to 17 months for patients without secondary ICU readmission (p=0.008). Multivariable analysis identified "preoperative administration of dexamethasone > 7 days" (p=0.002) as a significant and independent predictor of secondary unplanned ICU admission. Secondary ICU readmission following surgery for newly diagnosed glioblastoma is significantly associated with poor survival and thus may negate surgically achieved prerequisites for further treatment. This underlines the indispensability of precise patient selection as well as the importance of further scientific debate on these highly relevant aspects for patient safety.

Red blood cell distribution width to platelet ratio substantiates preoperative survival prediction in patients with newly-diagnosed glioblastoma

Object

The conception of individual patient-adjusted treatment strategies is constantly emerging in the field of neuro-oncology. Systemic laboratory markers may allow insights into individual needs and estimated treatment benefit at an earliest possible stage. Therefore, the present study was aimed at analyzing the prognostic significance of preoperative routine laboratory values in patients with newly-diagnosed glioblastoma.

Methods

Between 2014 and 2019, 257 patients were surgically treated for newly-diagnosed glioblastoma at the Neuro-Oncology Center of the University Hospital Bonn. Preoperative routine laboratory values including red blood cell distribution width (RDW) and platelet count were reviewed. RDW to platelet count ratio (RPR) was calculated and correlated to overall survival (OS) rates.

Results

Median preoperative RPR was 0.053 (IQR 0.044–0.062). The receiver operating characteristic (ROC) curve indicated an optimal cut-off value for RPR to be 0.05 (AUC 0.62; p = 0.002, 95% CI 0.544–0.685). 101 patients (39%) presented with a preoperative RPR < 0.05, whereas 156 patients (61%) had a RPR ≥ 0.05. Patients with preoperative RPR < 0.05 exhibited a median OS of 20 months (95% CI 17.9–22.1), which was significantly higher compared to a median OS of 13 months (95% CI 10.9–15.1) in patients with preoperative RPR ≥ 0.05 (p < 0.001).

Conclusions

The present study suggests the RPR to constitute a novel prognostic inflammatory marker for glioblastoma patients in the course of preoperative routine laboratory examinations and might contribute to a personalized medicine approach.

Perseveration in a spatial-discrimination serial reversal learning task is differentially affected by MAO-A and MAO-B inhibition and associated with reduced anxiety and peripheral serotonin levels

RATIONALE

Impairments in behavioral flexibility lie at the core of anxiety and obsessive-compulsive disorders. Few studies, however, have investigated the neural substrates of natural variation in behavioral flexibility and whether inflexible behavior is linked to anxiety and peripheral markers of stress and monoamine function.

OBJECTIVE

The objective of the study was to investigate peripheral and central markers associated with perseverative behavior on a spatial-discrimination serial reversal learning task.

METHODS

Rats were trained on a reversal learning task prior to blood sampling, anxiety assessment, and the behavioral evaluation of selective monoamine oxidase-A (MAO-A) and MAO-B inhibitors, which block the degradation of serotonin (5-HT), dopamine (DA), and noradrenaline (NA).

RESULTS

Perseveration correlated positively with 5-HT levels in blood plasma and inversely with trait anxiety, as measured on the elevated plus maze. No significant relationships were found between perseveration and the stress hormone corticosterone or the 5-HT precursor tryptophan. Reversal learning was significantly improved by systemic administration of the MAO-A inhibitor moclobemide but not by the MAO-B inhibitor lazabemide. Moclobemide also increased latencies to initiate a new trial following an incorrect response suggesting a possible role in modulating behavioral inhibition to negative feedback. MAO-A but not MAO-B inhibition resulted in pronounced increases in 5-HT and NA content in the orbitofrontal cortex and dorsal raphé nuclei and increased 5-HT and DA content in the basolateral amygdala and dorsomedial striatum.

CONCLUSIONS

These findings indicate that central and peripheral monoaminergic mechanisms underlie inter-individual variation in behavioral flexibility, which overlaps with trait anxiety and depends on functional MAO-A activity.

Conditioned taste aversion as a learning and memory paradigm

Conditioned taste aversion (CTA) is a well established learning and memory paradigm in rats and mice that is considered to be a special form of classical conditioning. Rodents--as well as many other species including man--learn to associate a novel taste (CS) with nausea (US), and as a consequence avoid drinking fluid with this specific taste. In contrast to other types of classical conditioning, even CS-US intervals lasting several hours lead to an aversion to the gustatory CS. With increasing CS-US delay duration, however, the aversion against the CS gradually decreases. Mice differ from rats in their reaction to the CS as well as the US. They tolerate a much higher concentration of saccharin and they do not show any clear signs of nausea when injected with the US. Advantages of this task are its relative independence of motor behavior, well described pathways for the CS and partly the US, and the wealth of available anatomical and pharmacological data implying several brain structures (e.g. parabrachial nucleus, amygdala, insular cortex), neurotransmitters and their receptors (e.g. cholinergic system, NMDA-receptors), and cellular processes (e.g. expression of immediate early genes, Ras-MAP kinase signaling pathway, CREB phosphorilation, protein tyrosine phosphorilation, protein synthesis) in CTA. The CTA paradigm has also been successfully used to phenotype mouse mutants.

Noradrenergic receptor mechanisms in neophobia

We have previously demonstrated that depletion of forebrain norepinephrine (NE) led to an attenuation of neophobia in a novel environment, as defined by a greater preference for novel food over familiar food. To study further the role of forebrain NE in neophobia we chronically infused noradrenergic receptor ligands or forskolin into the lateral ventricles of sham and 6-hydroxydopamine dorsal bundle lesioned rats. Chronic NE infusions into lesioned animals reversed the lesion-induced shift in relative food preference. The beta receptor agonist isoproterenol had moderate effects similar to those of NE in lesioned and sham animals. Phenylephrine, an alpha-1 agonist, was without effect. Forskolin, an adenylate cyclase activator, mimicked the effects of NE infusions. These data suggest a role for noradrenergic stimulation of adenylate cyclase in neophobia.

Activation of the noradrenergic system facilitates an attentional shift in the rat

The noradrenergic system was pharmacologically activated with the alpha 2 receptor antagonist, idazoxan (2 mg/kg i.p.), during the acquisition of a complex appetitive task requiring a shift in attention to stimulus dimension and in response strategy. Rats first learned a fixed path of 6 successive choices in a linear maze. The task was then changed to a visual discrimination task in which the spatial configuration of the correct path was indicated by visual cues and changed on each daily trial. During this part of the task, the rats were injected before each trial with idazoxan, a drug which increases the firing rate of neurons in the locus coeruleus and the release of noradrenaline in the cortex and hippocampus. Two control experiments showed that the drug treatment had no effect on the acquisition of either component of the task - the successive place learning or the visual discrimination. The drug was found to be effective only during the shift phase of the experiment, the idazoxan-treated rats taking fewer trials to reach criterion than the saline. A second experiment showed that idazoxan increased the amount of time spent investigating novel and unexpected objects in a familiar hole board. These results implicate the noradrenergic system in problem-solving which requires an attentional shift or a shift in responding from familiar to novel stimuli.

Forebrain norepinephrine involvement in selective attention and neophobia

It has been reported that depletion of forebrain norepinephrine via 6-hydroxydopamine infusion into the dorsal bundle decreases the rat's ability to selectively attend to relevant stimuli and thus increases the rat's responsiveness to novelty. In this study we measured 6-hydroxydopamine lesion effects on 1) selective attention via the nonreversal shift task and extinction of continuous reinforcement bar pressing and on 2) neophobia via consumption of a novel solution in a familiar environment; exploratory behaviors and consumption of a familiar food in a novel environment; and consumption of familiar and novel foods in a novel environment. Our data do not support a role for the dorsal bundle in selective attention. Our data do support a role for forebrain norepinephrine in neophobia and suggest that the lesion effects on neophobia result from an interaction between novelty of environment and novelty of food.