Dopamine D_2-receptor activation elicits akinesia, rigidity, catalepsy, and tremor in mice expressing hypersensitive 4 nicotinic receptors via a cholinergic-dependent mechanism

Recent studies suggest that high-affinity neuronal nicotinic acetylcholine receptors (nAChRs) containing α4 and β2 subunits (α4β2*) functionally interact with G-protein-coupled dopamine (DA) D_2 receptors in basal ganglia. We hypothesized that if a functional interaction between these receptors exists, then mice expressing an M2 point mutation (Leu9'Ala) rendering 4 nAChRs hypersensitive to ACh may exhibit altered sensitivity to a D_2-receptor agonist. When challenged with the D_(2)R agonist, quinpirole (0.5–10 mg/kg), Leu9'Ala mice, but not wild-type (WT) littermates, developed severe, reversible motor impairment characterized by rigidity, catalepsy, akinesia, and tremor. While striatal DA tissue content, baseline release, and quinpirole-induced DA depletion did not differ between Leu9'Ala and WT mice, quinpirole dramatically increased activity of cholinergic striatal interneurons only in mutant animals, as measured by increased c-Fos expression in choline acetyltransferase (ChAT)-positive interneurons. Highlighting the importance of the cholinergic system in this mouse model, inhibiting the effects of ACh by blocking muscarinic receptors, or by selectively activating hypersensitive nAChRs with nicotine, rescued motor symptoms. This novel mouse model mimics the imbalance between striatal DA/ACh function associated with severe motor impairment in disorders such as Parkinson’s disease, and the data suggest that a D_(2)R–α4*-nAChR functional interaction regulates cholinergic interneuron activity.—Zhao-Shea, R., Cohen, B. N., Just, H., McClure-Begley, T., Whiteaker, P., Grady, S. R., Salminen, O., Gardner, P. D., Lester, H. A., Tapper, A. R. Dopamine D2-receptor activation elicits akinesia, rigidity, catalepsy, and tremor in mice expressing hypersensitive α4 nicotinic receptors via a cholinergic-dependent mechanism

Chronic Nicotine Cell Specifically Upregulates Functional α4* Nicotinic Receptors: Basis for Both Tolerance in Midbrain and Enhanced Long-Term Potentiation in Perforant Path

Understanding effects of chronic nicotine requires identifying the neurons and synapses whose responses to nicotine itself, and to endogenous acetylcholine, are altered by continued exposure to the drug. To address this problem, we developed mice whose α4 nicotinic receptor subunits are replaced by normally functioning fluorescently tagged subunits, providing quantitative studies of receptor regulation at micrometer resolution. Chronic nicotine increased α4 fluorescence in several regions; among these, midbrain and hippocampus were assessed functionally. Although the midbrain dopaminergic system dominates reward pathways, chronic nicotine does not change α4* receptor levels in dopaminergic neurons of ventral tegmental area (VTA) or substantia nigra pars compacta. Instead, upregulated, functional α4* receptors localize to the GABAergic neurons of the VTA and substantia nigra pars reticulata. In consequence, GABAergic neurons from chronically nicotine-treated mice have a higher basal firing rate and respond more strongly to nicotine; because of the resulting increased inhibition, dopaminergic neurons have lower basal firing and decreased response to nicotine. In hippocampus, chronic exposure to nicotine also increases α4* fluorescence on glutamatergic axons of the medial perforant path. In hippocampal slices from chronically treated animals, acute exposure to nicotine during tetanic stimuli enhances induction of long-term potentiation in the medial perforant path, showing that the upregulated α4* receptors in this pathway are also functional. The pattern of cell-specific upregulation of functional α4* receptors therefore provides a possible explanation for two effects of chronic nicotine: sensitization of synaptic transmission in forebrain and tolerance of dopaminergic neuron firing in midbrain

Chronic Nicotine Cell Specifically Upregulates Functional α4* Nicotinic Receptors: Basis for Both Tolerance in Midbrain and Enhanced Long-Term Potentiation in Perforant Path

Understanding effects of chronic nicotine requires identifying the neurons and synapses whose responses to nicotine itself, and to endogenous acetylcholine, are altered by continued exposure to the drug. To address this problem, we developed mice whose α4 nicotinic receptor subunits are replaced by normally functioning fluorescently tagged subunits, providing quantitative studies of receptor regulation at micrometer resolution. Chronic nicotine increased α4 fluorescence in several regions; among these, midbrain and hippocampus were assessed functionally. Although the midbrain dopaminergic system dominates reward pathways, chronic nicotine does not change α4* receptor levels in dopaminergic neurons of ventral tegmental area (VTA) or substantia nigra pars compacta. Instead, upregulated, functional α4* receptors localize to the GABAergic neurons of the VTA and substantia nigra pars reticulata. In consequence, GABAergic neurons from chronically nicotine-treated mice have a higher basal firing rate and respond more strongly to nicotine; because of the resulting increased inhibition, dopaminergic neurons have lower basal firing and decreased response to nicotine. In hippocampus, chronic exposure to nicotine also increases α4* fluorescence on glutamatergic axons of the medial perforant path. In hippocampal slices from chronically treated animals, acute exposure to nicotine during tetanic stimuli enhances induction of long-term potentiation in the medial perforant path, showing that the upregulated α4* receptors in this pathway are also functional. The pattern of cell-specific upregulation of functional α4* receptors therefore provides a possible explanation for two effects of chronic nicotine: sensitization of synaptic transmission in forebrain and tolerance of dopaminergic neuron firing in midbrain

The establishment, maintenance, and adaptation of high- and low-impact chronic pain: a framework for biopsychosocial pain research

We present a framework for the study of states of chronic pain and transitions between those states. We capture in the framework the dynamic nature of pain: people live with pain that changes over time. First, we offer definitions of both acute and chronic pain and explore the contextual considerations related to the common use of this temporal dichotomy. Second, we promote the importance of incorporating the impact pain has on a person's life. Finally, we discuss the challenges and opportunities inherent in implementing this common approach. Our goal is to produce a framework for the study of the development, maintenance, and resolution of chronic pain. Whether a single brief event or a constant feature of life, pain interrupts to prioritise protection, interferes with activity, reduces quality of life, and can alter identity.44 Protection is achieved by escape from harm, avoidance of perceived danger, withdrawal for respite and repair, and communication of incapacity and environmental risk; longer-term protection is achieved by learning the cues for pain and injury.53 From this perspective, pain is most usefully considered a need state, fundamentally a motivational drive to protect.49 This approach centres our attention on the consequences of pain for the person in their context, on its duration and its impact

A call for transparent reporting to optimize the predictive value of preclinical research

The US National Institute of Neurological Disorders and Stroke convened major stakeholders in June 2012 to discuss how to improve the methodological reporting of animal studies in grant applications and publications. The main workshop recommendation is that at a minimum studies should report on sample-size estimation, whether and how animals were randomized, whether investigators were blind to the treatment, and the handling of data. We recognize that achieving a meaningful improvement in the quality of reporting will require a concerted effort by investigators, reviewers, funding agencies and journal editors. Requiring better reporting of animal studies will raise awareness of the importance of rigorous study design to accelerate scientific progress

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Wake up and Call. by Sharon Begley

In Kyoto, the world takes a historic first step toward turning down the heat

Giant swiss collider may reveal secrets about origins of mass

"This year, the Large Hadron Collider, a nearly $4 billions accelerator at the CERN physics lab near Geneva, will be switched on. When it is, it may produce new kinds of matter that nature had hidden from human eyes - extra dimensions of space concealed within the mundance three, like a secret compartment in a suitcase, and a mysterious field that gives matter mass." (2,5 pages