Systemic and intra-amygdala administrations of midazolam reverse anxiety-like behavior induced by cohabiting with a cagemate in chronic pain condition

The affective component of pain may be shared among conspecifics through emotional contagion, a form of empathic expression. In this sense, reverberation of negative emotions could generate distress behavioral responses, such as pathological anxiety. Evidences reported that amygdala and its benzodiazepine receptors are involved in perception of pain in others. However, relatively little is known about the neural processes underlying emotional contagion induced by pain observation. In the present study, we investigated the effects of midazolam, an allosteric GABAergic receptor agonist, in anxiety-like behaviors induced by cohabitation with cagemate submitted to sciatic nerve constriction. For this purpose, we administrated systemic (0.5, 1.0 and 2.0 mg/kg) and intra-amygdala midazolam injections (3.0 and 30.0 nmol) in observer cagemates before elevated plus-maze (EPM) evaluation. We found that mice subjected to nerve constriction and their observer cagemates increased anxiety-like behavior in the EPM. Further, systemically (1.0 and 2.0 mg/kg) and intra-amygdala administration of midazolam (3.0 and 30 nmol) reverse this anxiogenic effect. Collectively, these results suggest that social interaction with a cagemate under chronic pain produces anxiety-like responses that could be blocked through midazolam application.

Antibiotics and the Nervous System—Which Face of Antibiotic Therapy Is Real, Dr. Jekyll (Neurotoxicity) or Mr. Hyde (Neuroprotection)?

Antibiotics as antibacterial drugs have saved many lives, but have also become a victim of their own success. Their widespread abuse reduces their anti-infective effectiveness and causes the development of bacterial resistance. Moreover, irrational antibiotic therapy contributes to gastrointestinal dysbiosis, that increases the risk of the development of many diseases, including neurological and psychiatric. One of the potential options for restoring homeostasis is the use of oral antibiotics that are poorly absorbed from the gastrointestinal tract (e.g., rifaximin alfa). Thus, antibiotic therapy may exert neurological or psychiatric adverse drug reactions which are often considered to be overlooked and undervalued issues. Drug-induced neurotoxicity is mostly observed after beta-lactams and quinolones. Penicillin may produce a wide range of neurological dysfunctions, including encephalopathy, behavioral changes, myoclonus or seizures. Their pathomechanism results from the disturbances of gamma-aminobutyric acid-GABA transmission (due to the molecular similarities between the structure of the β-lactam ring and GABA molecule) and impairment of the functioning of benzodiazepine receptors (BZD). However, on the other hand, antibiotics have also been studied for their neuroprotective properties in the treatment of neurodegenerative and neuroinflammatory processes (e.g., Alzheimer’s or Parkinson’s diseases). Antibiotics may, therefore, become promising elements of multi-targeted therapy for these entities.

EMBRIOGENESIS OF NEURONAL ELENENTS (GLIOBLASTS AND GABAA RECEPTORS) IN THE HUMAN BRAIN NEUROIMMUNE SYSTEM UNDER PRENATAL ALCOHOL EXPOSURE

Exposure to alcohol causes imbalances in neuroimmune function and impaired brain development. Alcohol activates the innate immune signaling pathways in the brain. Neuroimmune molecules expressed and secreted by glial cells of the brain (microglia, oligodendroglia) alter the function of neurons and further stimulate the development of alcoholic behavior. Various signaling pathways and brain cells are involved in the transmission of neuroimmune signals. Glial cells are the main sources of immune mediators in the brain, which respond to and release immune signals in the central nervous system. The aim of this study was to study neuronal elements: morphometric parameters of glioblasts, synaptic structures and properties of synaptosomal GABAA-benzodiazepine receptors of the neuroimmune system in the embryogenesis of the human brain under perinatal exposure to alcohol. Changes in glioblasts in the brain tissue of human embryos and fetuses were revealed under conditions of chronic prenatal alcoholization with an increase in gestational age compared with control subgroups: a significant increase in the average number of glioblasts, the length of the perimeters of presynaptic terminal structures, postsynaptic density, presynaptic terminal regions were significantly less (p < 0.01) in the study group than in the control comparison group. Exposure to ethanol leads to a decrease in the affinity of GABAA-benzodiazepine receptors, which affects neuronal plasticity associated with the development and differentiation of progenitor cells (glioblasts and neuroblasts) during embryogenesis of the human brain and leads to suppression of GABAergic function in the brain. This causes a disruption in the interconnection of embryonic cells in the brain, leads to excessive apoptosis due to the activation of glial cells of the nervous tissue, disruption of neuroimmune function in the developing brain, changes in neuronal circuits, as well as a change in the balance of excitatory and inhibitory effects, which affects the functional activity in the central nervous system. Glial activation is a compensatory reaction caused by neuroplastic changes aimed at adapting the developing brain of the embryo and fetus under conditions of neurotoxicity and hypoxia under the influence of prenatal alcoholization of the maternal organism and the effect of ethanol on the fetus. The dynamics of changes in glial elements and receptor activity in the nervous tissue of human embryos and fetuses under conditions of prenatal exposure to alcohol indicates a more pronounced effect of alcohol on the earliest stages of human embryo development, which is of great practical importance in planning pregnancy and the inadmissibility of alcoholization of the mother in order to avoid negative consequences in offspring.

An In Vivo Study of a Rat Fluid-Percussion-Induced Traumatic Brain Injury Model with [11C]PBR28 and [18F]flumazenil PET Imaging

Traumatic brain injury (TBI) modelled by lateral fluid percussion-induction (LFPI) in rats is a widely used experimental rodent model to explore and understand the underlying cellular and molecular alterations in the brain caused by TBI in humans. Current improvements in imaging with positron emission tomography (PET) have made it possible to map certain features of TBI-induced cellular and molecular changes equally in humans and animals. The PET imaging technique is an apt supplement to nanotheranostic-based treatment alternatives that are emerging to tackle TBI. The present study aims to investigate whether the two radioligands, [11C]PBR28 and [18F]flumazenil, are able to accurately quantify in vivo molecular-cellular changes in a rodent TBI-model for two different biochemical targets of the processes. In addition, it serves to observe any palpable variations associated with primary and secondary injury sites, and in the affected versus the contralateral hemispheres. As [11C]PBR28 is a radioligand of the 18 kD translocator protein, the up-regulation of which is coupled to the level of neuroinflammation in the brain, and [18F]flumazenil is a radioligand for GABAA-benzodiazepine receptors, whose level mirrors interneuronal activity and eventually cell death, the use of the two radioligands may reveal two critical features of TBI. An up-regulation in the [11C]PBR28 uptake triggered by the LFP in the injured (right) hemisphere was noted on day 14, while the uptake of [18F]flumazenil was down-regulated on day 14. When comparing the left (contralateral) and right (LFPI) hemispheres, the differences between the two in neuroinflammation were obvious. Our results demonstrate a potential way to measure the molecular alterations in a rodent-based TBI model using PET imaging with [11C]PBR28 and [18F]flumazenil. These radioligands are promising options that can be eventually used in exploring the complex in vivo pharmacokinetics and delivery mechanisms of nanoparticles in TBI treatment.

Benzodiazepine Receptors in the Periphery

The benzodiazepines are almost universally thought to produce one and only one pharmacologic effect: positive allosteric modulation of GABAA receptors located in the brain. This results in an increased Cl−ion influx, greater negative transmembrane potential difference, and neurons that are less likely to fire in response to anxiety-producing stimulation. Unfortunately, the simplicity and success of this mono-target belief has distracted researchers and clinicians from studying and appreciating their other pharmacology. A glaring example is the general lack of awareness of the peripheral benzodiazepine receptor. The peripheral benzodiazepine receptor alters mitochondrial function (energy supply), cholesterol transport, and immune function. A patient who is on long-term benzodiazepine therapy (or withdrawing from them) will have these sites affected, just as are the sites located in the brain. One can easily imagine that the adverse effects associated with the peripheral sites would be fundamental, varied, and potentially profound—involving lack of energy, altered cholesterol metabolism, and aberrant immune function.