Opioid modulation of GABA release in the rat inferior colliculus

Background: The inferior colliculus, which receives almost all ascending and descending auditory signals, plays a crucial role in the processing of auditory information. While the majority of the recorded activities in the inferior colliculus are attributed to GABAergic and glutamatergic signalling, other neurotransmitter systems are expressed in this brain area including opiate peptides and their receptors which may play a modulatory role in neuronal communication.Results: Using a perfusion protocol we demonstrate that morphine can inhibit KCl-induced release of [H-3] GABA from rat inferior colliculus slices. DAMGO ([D-Ala(2), N-Me-Phe(4), Gly(5)ol]-enkephalin) but not DADLE ([D-Ala2, D-Leu5]-enkephalin or U69593 has the same effect as morphine indicating that mu rather than delta or kappa opioid receptors mediate this action. [H-3]GABA release was diminished by 16%, and this was not altered by the protein kinase C inhibitor bisindolylmaleimide I. Immunostaining of inferior colliculus cryosections shows extensive staining for glutamic acid decarboxylase, more limited staining for mu opiate receptors and relatively few neurons co-stained for both proteins.Conclusion: The results suggest that mu-opioid receptor ligands can modify neurotransmitter release in a sub population of GABAergic neurons of the inferior colliculus. This could have important physiological implications in the processing of hearing information and/or other functions attributed to the inferior colliculus such as audiogenic seizures and aversive behaviour

Jigsaw Recovery: The Spatio-temporalities of Alcohol Abuse and Recovery in a Non-interventionist, Peer-led Service

Research highlights that recovery from substance use is a process facilitated by relational factors, resources and therapeutic practices embedded in places conducive to recovery. However, the accessibility of such resources for those with complex needs, and the therapeutic potential of peer-led spaces needs contextualizing in both time and place. We examined the characteristics of a social space employing a noninterventionist peer-led approach for active alcohol users. Individuals prioritized the management of everyday life over recovery, especially abstinence. This space acted as a replacement “jigsaw”; interrupting the temporal, spatial and social aspects of active use. Flexible approaches allowing choice in recovery pathways appear significant for this population

G-protein αq gene expression plays a role in alcohol tolerance in Drosophila melanogaster

Ethanol is a psychoactive substance causing both short- and long-term behavioural changes in humans and animal models. We have used the fruit fly Drosophila melanogaster to investigate the effect of ethanol exposure on the expression of the Gαq protein subunit. Repetitive exposure to ethanol causes a reduction in sensitivity (tolerance) to ethanol, which we have measured as the time for 50% of a set of flies to become sedated after exposure to ethanol (ST50). We demonstrate that the same treatment that induces an increase in ST50 over consecutive days (tolerance) also causes a decrease in Gαq protein subunit expression at both the messenger RNA and protein level. To identify whether there may be a causal relationship between these two outcomes, we have developed strains of flies in which Gαq messenger RNA expression is suppressed in a time- and tissue-specific manner. In these flies, the sensitivity to ethanol and the development of tolerance are altered. This work further supports the value of Drosophila as a model to dissect the molecular mechanisms of the behavioural response to alcohol and identifies G proteins as potentially important regulatory targets for alcohol use disorders

On the effects of a beam-like piezoelectric passive controller on the linear stability of the visco-elastic Beck's beam

The linear stability of the visco-elastic Beck's beam is investigated in this paper. The mechanical system is equipped with a piezoelectric distributed controller, whose governing equation of motion in linear dynamics resembles that of the beam, in except for the second-order spatial derivative term related to the follower force. Suitable passive control strategies are explored with the aim to increase the Hopf bifurcation critical load, triggered by the presence of the follower force in the mechanical sub-system. The equations of motion of the resultant Piezo-Electro-Mechanical (PEM) system are derived via a variational approach and discretized through the Galerkin method. The linear stability analysis of the PEM system is carried out by solving the descending eigenvalue problem. In this framework, parametric investigations are developed in order to investigate the effects of the electrical parameters on the stability of the system

Self-activated morphing carbon fiber composites via cyclic internal stresses

An innovative concept to exploit self-activated morphing composite materials is presented and demonstrated experimentally. In this design, shape changes of a carbon fiber composite are achieved by combining two key ingredients: fibers orientation and temperature-sensitive epoxy resin. When the fibers are properly oriented in each layer, internal stresses can be induced or gradually released by hardening or softening, respectively, the hosting epoxy resin. The epoxy resin stiffness is controlled with the help of internal heaters (e.g. the carbon fibers as demonstrated in this paper). The proposed mechanism results in a large scale and cyclic shape-changing capability which, together with the corresponding tunable stiffness, represent the fundamental features of morphing structural materials

On the effectiveness of a rod-like distributed piezoelectric controller in preventing the Hopf bifurcation of the visco-elastic Beck’s beam

The linear stability of a piezo-electro-mechanical (PEM) system subject to a follower force is here discussed. The mechanical subsystem is constituted by a linear visco-elastic cantilever beam, loaded by a follower force at the free end. It suffers from the Hopf bifurcation, whose critical load is strongly affected by damping, according to the well-known Ziegler’s paradox. On the other hand, the electrical subsystem consists of a distributed array of piezoelectric patches attached to the beam and connected to a properly designed second-order analog circuit, aiming at possibly enhancing the stability of the PEM system. The partial differential equations of motion of the PEM system are discretized by the Galerkin method. Linear stability analysis is then carried out by numerically solving the associated eigenvalue problem, for different significant values of the electrical parameters. A suitable perturbation method is also adopted to detect the role of the electrical parameters and discuss the effectiveness of the controller

A rod-like piezoelectric controller for the improvement of the visco-elastic Beck's beam linear stability

The linear stability of a cantilever beam subject to a follower force is investigated. A system of distributed piezoelectric devices is attached to the beam with the purpose of improving the dynamic stability of the structure. They are connected to a second-order network and second-order analog electrical circuit. The assembly of the mechanical and piezoelectric subsystems constitutes a coupled Piezo-Electro-Mechanical (PEM) system, whose equations of motion, derived within a variational approach, are discretized via the Galerkin weighted residual method and the stability of the trivial equilibrium is addressed by numerically solving the associated eigenvalue problem. A sensitivity analysis, carried out on a numerical ground, is thus conducted on a wide range of the electrical parameters to investigate the effectiveness of the proposed controller

Tailoring of pinched hysteresis for nonlinear vibration absorption via asymptotic analysis

The method of multiple scales is adopted to investigate the dynamic response of a nonlinear Vibration Absorber (VA) whose constitutive behavior is governed by hysteresis with pinching. The asymptotic analysis is first devoted to study the response of the absorber to harmonic excitations and to evaluate its sensitivity to the main constitutive parameters. The frequency response obtained in closed form allows to carry out the stability analysis together with a parametric study leading to behavior charts characterizing multi-valued softening/hardening responses or single-valued, quasi-linear responses. A two-degree-of-freedom model of a primary nonlinear structure endowed with the hysteretic vibration absorber is investigated to explore transfers of energy from the structure to the absorber resulting into optimal vibration amplitude reduction. The asymptotic solution is proved to be in good agreement with the numerical solution obtained via continuation. The asymptotic approach is embedded into a differential evolutionary algorithm to obtain a multi-parameter optimization procedure by which the optimal hysteresis parameters are found

Dynamic response to transverse loading of a single-layered tubular beam via a perturbation approach

A beam-like model is proposed to address nonlinear dynamic response of a thin pipe, under the action of a resonant transverse load. The mechanical model consists of a Timoshenko beam enriched with further kinematic and dynamic variables which, besides extension and bending, consistently describe local effects, related to ovalization and warping of the cross-section. The nonlinear equations of motions are derived via the principle of virtual work, and internal resonance between the global and local modes is addressed by the multiple scale method, after a Galerkin projection of the equations on the first significant modes. The softening behavior induced by the local deformation remarkably affects the asymptotic solution, which turns out to be in good agreement with that provided by numerical integration