Yvonne Lang

Endocannabinoid-mediated enhancement of fear-conditioned analgesia in rats: Opioid receptor dependency and molecular correlates

Abstract The opioid and endocannabinoid systems mediate analgesia expressed upon re‐exposure to a contextually aversive stimulus (fear‐conditioned analgesia; FCA), and modulate the mitogen‐activated protein kinase (MAPK) pathway. However, an interaction between the opioid and endocannabinoid systems during FCA has not been investigated at the behavioural or molecular level. FCA was modeled in male Lister‐hooded rats by assessing formalin‐evoked nociceptive behaviour in an arena previously paired with footshock. Administration of the fatty acid amide hydrolase and endocannabinoid catabolism inhibitor, URB597 (0.3 mg/kg, i.p.), enhanced expression of FCA. The opioid receptor antagonist, naloxone, attenuated FCA and attenuated the URB597‐induced enhancement of FCA. SR141716A (CB1 antagonist) and SR144528 (CB2 antagonist) also attenuated the URB597‐mediated enhancement of FCA. Expression of FCA was associated with increased relative phospho‐ERK2 expression in the amygdala, an effect blocked by naloxone, SR141716A, and SR144528. Furthermore, URB597‐mediated enhancement of FCA was associated with reduced phospho‐ERK1 and phospho‐ERK2 in the amygdala. Phospho‐ERK1/2 expression in the hippocampus, prefrontal cortex, and thalamus was unchanged following FCA and drug treatment. None of the drugs affected formalin‐evoked nociceptive behaviour or phospho‐ERK1/2 expression in non‐fear‐conditioned rats. These data suggest that endocannabinoid‐mediated enhancement of FCA is abolished by pharmacological blockade of opioid receptors as well as CB1 or CB2 receptors. Both pharmacological enhancement (with URB597) and attenuation (with naloxone) of this form of endogenous analgesia were associated with reduced expression of phospho‐ERK1/2 in the amygdaloid complex arguing against a causal role for ERK1/2 signaling in the amygdala during expression of FCA or its modulation by opioids or cannabinoids.

Alterations in extracellular levels of gamma-aminobutyric acid in the rat basolateral amygdala and periaqueductal gray during conditioned fear, persistent pain and fear-conditioned analgesia.

UNLABELLED Evidence suggests an important role for supraspinal gamma-aminobutyric acid (GABA) in conditioned fear and pain. Using dual probe microdialysis coupled to HPLC, we investigated alterations in extracellular levels of GABA simultaneously in the rat basolateral amygdala and dorsal periaqueductal gray during expression of conditioned fear, formalin-evoked nociception, and fear-conditioned analgesia. Re-exposure to a context previously paired with footshock significantly increased the duration of freezing and 22-kilohertz ultrasonic vocalization, and reduced formalin-evoked nociceptive behavior. Upon re-exposure to the context, GABA levels in the basolateral amygdala were significantly lower in fear-conditioned animals compared with non-fear-conditioned controls, irrespective of intraplantar formalin/saline injection. GABA levels in the dorsal periaqueductal gray were lower in rats receiving intraplantar injection of formalin, compared with saline-treated controls. GABA levels sampled were sensitive to nipecotic acid and calcium infusion. No specific fear-conditioned analgesia-related alterations in GABA efflux were observed in these regions despite the ability of rats undergoing dual probe microdialysis to express this important survival response. In conclusion, expression of contextually induced fear- and pain-related behavior are accompanied by suppression of GABA release in the basolateral amygdala and dorsal periaqueductal gray, respectively, compared with non-fear, non-pain controls. PERSPECTIVE This study investigates alterations in levels of the neurotransmitter GABA simultaneously in the rat amygdala and periaqueductal grey during expression of pain- and fear-related behavior and fear-induced analgesia. The results enhance our understanding of the role of this neurotransmitter in pain, memory of pain and control of pain during fear.

Integration of TiO2 into the diatom Thalassiosira weissflogii during frustule synthesis

Nature has inspired the design of complex hierarchical structures in the field of material science. Diatoms, unicellular algae with a hallmark intricate siliceous cell wall, have provided such a stimulus. Altering the chemistry of the diatom frustule has been explored to expand on the potential application of diatoms. The ability to modify the diatom in vivo opens the possibility to tailor the diatom to the end application. Herein, we report the chemical modification of the living diatom T. weissflogii using a titania precursor, titanium (IV) bis-(ammonium lactato)-dihydroxide (TiBALDH). Incorporation of Ti into the diatom is achieved via repeated treatment of cultures with non-toxic concentrations of TiBALDH. The characteristic architectural features of the diatom are unaltered following chemical modification. Transformation of the living diatom provides opportunity to confer novel structural, chemical or functional properties upon the diatom. We report on a photocatalytic ability imparted upon the TiBALDH-modified diatom.

Functionalization of the living diatom Thalassiosira weissflogii with thiol moieties

Biomineralization processes identified within diatoms have inspired the design of synthetic silica structures in vitro using alkoxysilane precursors. Here we explore the use of the machinery within the living diatom to fabricate organo-silica constructs using a combination of alkoxysilane and organoalkoxysilane precursors. We report on the incorporation of thiol moieties into the diatom during frustule synthesis. Formation of valves within the parent diatom is monitored using fluorescence microscopy, and the modification of the chemical composition of the diatom is confirmed using energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and (29)Si-nuclear magnetic resonance spectroscopy. Chemical modification is achieved without loss of the nano-scale architectural features of the frustule. Extension of this work may allow the chemistry of the diatom to be tailored during synthesis.

Nano‐Structured Polymer‐Silica Composite Derived from a Marine Diatom via Deactivation Enhanced Atom Transfer Radical Polymerization Grafting

Nature exhibits phenomenally intricate architecture in various organisms and it is through these structures that researchers in the fi eld of materials science derive inspiration in creating new biomaterials. [ 1 ] One such organism that has drawn attention due to its architecture is the diatom, a unicellular algae, which has a characteristic ornate siliceous cell wall (known as a “frustule”) that current engineering practices cannot fabricate. The proposed applications for diatoms in catalysis, [ 2 ] separation science, [ 3 ] and optics [ 4 ] are heavily dependent on the architecture of the diatom. There has been an interest in altering the chemistry of the frustule, and replication of the frustule in order to expand on possible applications frustule. [ 5 ] Inorganic replicas have predominated: (i) MgO, [ 5a ] TiO 2 , [ 5b ] and ZrO 2 [ 5c ] replicas via gas/solid displacement reactions, and (ii) gold replicas by electroless deposition. [ 5d ] There has been a paucity of reports describing the generation of organic replicas. [ 6 ]

Synthesis of polymer-silica hybrid microparticles with defined geometry using surface initiated atom transfer radical polymerization

Nanostructured polymer/silica hybrid materials have gained attention as they combine the advantageous properties of organic and inorganic materials in one entity. Herein, we report incorporation of chloromethyl moieties into a living diatom to prepare an alkyl-halide activated siliceous biotemplate. Subsequent, in situ polymerization via surface initiated atom transfer radical polymerization generated a polymer/silica microparticle with defined geometry.

Fabrication of nanopatterned polymeric microparticles using a diatom as a sacrificial template

Natural structures with complex hierarchical architecture are employed as biotemplates to fabricate constructs with both nano- and micro-scale features. Diatoms have served as templates for the preparation of inorganic constructs, but are under-explored for the preparation of organic constructs. Herein, we report a method to fabricate nanopatterned polymeric microparticles using the diatom as a sacrificial template.

The Multiple Roles of Diatoms in Environmental Applications: Prospects for Sol-Gel Modified Diatoms

Diatoms, unicellular microalgae, have a characteristic ornate siliceous cell wall, referred to as the frustule. The elaborate architecture of the frustule, at both the nano- and micro-scale, lends these structures to proposed applications in catalysis, separation science, filtration and emerging nanotechnologies. In addition, the living diatom is a known indicator of water quality, due to the fact that both the cell morphology and cell physiology are sensitive to the presence of pesticides, herbicides, pharmaceuticals, polymers and personal care products. The potential of diatoms to bioaccumulate, biotransform or biodegrade compounds of concern including polycyclic aromatic hydrocarbons, non-steroidal anti-inflammatory pharmaceuticals, endocrine disrupting chemicals, phthalates and metal nanoparticles has been documented. Sol-gel modification of either the living diatom or harvested frustule enables the design of diatoms for bioremediation of these priority substances from the environment. Furthermore, diatoms can be prodigious producers of extracellular polymeric substances (EPS) that may find a role in decontamination of pollutants through the formation gel-like networks that sequester pollutants.