Major depression is characterized by diverse debilitating symptoms that include hopelessness and anhedonia. Dopamine neurons involved in reward and motivation are among many neural populations that have been hypothesized to be relevant, and certain antidepressant treatments, including medications and brain stimulation therapies, can influence the complex dopamine system. Until now it has not been possible to test this hypothesis directly, even in animal models, as existing therapeutic interventions are unable to specifically target dopamine neurons. Here we investigated directly the causal contributions of defined dopamine neurons to multidimensional depression-like phenotypes induced by chronic mild stress, by integrating behavioural, pharmacological, optogenetic and electrophysiological methods in freely moving rodents. We found that bidirectional control (inhibition or excitation) of specified midbrain dopamine neurons immediately and bidirectionally modulates (induces or relieves) multiple independent depression symptoms caused by chronic stress. By probing the circuit implementation of these effects, we observed that optogenetic recruitment of these dopamine neurons potently alters the neural encoding of depression-related behaviours in the downstream nucleus accumbens of freely moving rodents, suggesting that processes affecting depression symptoms may involve alterations in the neural encoding of action in limbic circuitry.

Dopamine neurons modulate neural encoding and expression of depression-related behaviour

Cancer genome-sequencing studies have revealed a remarkably high prevalence of mutations in genes encoding subunits of the SWI/SNF chromatin-remodelling complexes, with nearly 25% of all cancers harbouring aberrations in one or more of these genes. A role for such aberrations in tumorigenesis is evidenced by cancer predisposition in both carriers of germline loss-of-function mutations and genetically engineered mouse models with inactivation of any of several SWI/SNF subunits. Whereas many of the most frequently mutated oncogenes and tumour-suppressor genes have been studied for several decades, the cancer-promoting role of mutations in SWI/SNF genes has been recognized only more recently, and thus comparatively less is known about these alterations. Consequently, increasing research interest is being focused on understanding the prognostic and, in particular, the potential therapeutic implications of mutations in genes encoding SWI/SNF subunits. Herein, we review the burgeoning data on the mechanisms by which mutations affecting SWI/SNF complexes promote cancer and describe promising emerging opportunities for targeted therapy, including immunotherapy with immune-checkpoint inhibitors, presented by these mutations. We also highlight ongoing clinical trials open specifically to patients with cancers harbouring mutations in certain SWI/SNF genes. Mutations in genes encoding subunits of the SWI/SNF chromatin-remodelling complexes occur in almost 25% of all cancers. Herein, Mittal and Roberts discuss the mechanisms by which these mutations might promote cancer and describe the associated vulnerabilities that provide opportunities for targeted therapy or immunotherapy with immune-checkpoint inhibitors.

The SWI/SNF complex in cancer — biology, biomarkers and therapy

Background
The use of peripheral nerve blocks for anesthesia and postoperative analgesia has increased significantly in recent years. Adjuvants are frequently added to local anesthetics to prolong analgesia following peripheral nerve blockade. Numerous randomized controlled trials and meta-analyses have examined the pros and cons of the use of various individual adjuvants.

/pdf/local-anesthetic-peripheral-nerve-block-adjuvants-for-22jshgwtq6.pdf

Local Anesthetic Peripheral Nerve Block Adjuvants for Prolongation of Analgesia: A Systematic Qualitative Review.

Although beneficial in acute and chronic pain management, the use of local anaesthetics is limited by its duration of action and the dose dependent adverse effects on the cardiac and central nervous system. Adjuvants or additives are often used with local anaesthetics for its synergistic effect by prolonging the duration of sensory-motor block and limiting the cumulative dose requirement of local anaesthetics. The armamentarium of local anesthetic adjuvants have evolved over time from classical opioids to a wide array of drugs spanning several groups and varying mechanisms of action. A large array of opioids ranging from morphine, fentanyl and sufentanyl to hydromorphone, buprenorphine and tramadol has been used with varying success. However, their use has been limited by their adverse effect like respiratory depression, nausea, vomiting and pruritus, especially with its neuraxial use. Epinephrine potentiates the local anesthetics by its antinociceptive properties mediated by alpha-2 adrenoreceptor activation along with its vasoconstrictive properties limiting the systemic absorption of local anesthetics. Alpha 2 adrenoreceptor antagonists like clonidine and dexmedetomidine are one of the most widely used class of local anesthetic adjuvants. Other drugs like steroids (dexamethasone), anti-inflammatory agents (parecoxib and lornoxicam), midazolam, ketamine, magnesium sulfate and neostigmine have also been used with mixed success. The concern regarding the safety profile of these adjuvants is due to its potential neurotoxicity and neurological complications which necessitate further research in this direction. Current research is directed towards a search for agents and techniques which would prolong local anaesthetic action without its deleterious effects. This includes novel approaches like use of charged molecules to produce local anaesthetic action (tonicaine and n butyl tetracaine), new age delivery mechanisms for prolonged bioavailability (liposomal, microspheres and cyclodextrin systems) and further studies with other drugs (adenosine, neuromuscular blockers, dextrans).

Adjuvants to local anesthetics: Current understanding and future trends

Chronic, pathological pain remains a global health problem and a challenge to basic and clinical sciences. A major obstacle to preventing, treating, or reverting chronic pain has been that the nature of neural circuits underlying the diverse components of the complex, multidimensional experience of pain is not well understood. Moreover, chronic pain involves diverse maladaptive plasticity processes, which have not been decoded mechanistically in terms of involvement of specific circuits and cause-effect relationships. This review aims to discuss recent advances in our understanding of circuit connectivity in the mammalian brain at the level of regional contributions and specific cell types in acute and chronic pain. A major focus is placed on functional dissection of sub-neocortical brain circuits using optogenetics, chemogenetics, and imaging technological tools in rodent models with a view towards decoding sensory, affective, and motivational-cognitive dimensions of pain. The review summarizes recent breakthroughs and insights on structure-function properties in nociceptive circuits and higher order sub-neocortical modulatory circuits involved in aversion, learning, reward, and mood and their modulation by endogenous GABAergic inhibition, noradrenergic, cholinergic, dopaminergic, serotonergic, and peptidergic pathways. The knowledge of neural circuits and their dynamic regulation via functional and structural plasticity will be beneficial towards designing and improving targeted therapies.

https://journals.physiology.org/doi/pdf/10.1152/physrev.00040.2019

Cellular Circuits in the Brain and Their Modulation in Acute and Chronic Pain.

Background
Dexmedetomidine (DEX) has been used under perioperative settings as an adjuvant to enhance the analgesic property of local anesthetics by some anesthesiologists. However, the analgesic mechanisms and neurotoxicity of DEX were poorly understood. This study examined the effect of DEX alone on inflammatory pain, and it also examined the underlying molecular mechanisms of DEX in the spinal cord. Furthermore, in vivo and in vitro experiments were performed to investigate the neurotoxicity of DEX on the spinal cord and cortical neurons.

/pdf/molecular-mechanisms-underlying-the-analgesic-property-of-gb272pzu9f.pdf

Molecular Mechanisms Underlying the Analgesic Property of Intrathecal Dexmedetomidine and Its Neurotoxicity Evaluation: An In Vivo and In Vitro Experimental Study

Brain-Derived Neurotrophic Factor in the Mesolimbic Reward Circuitry Mediates Nociception in Chronic Neuropathic Pain.

BRG1, a core component of the SWI/SNF chromatin-remodeling complex, has been implicated in cancer development; however, the biological significance of BRG1 in breast cancer remains unknown. We explored the role of BRG1 in human breast cancer pathogenesis. Using tissue microarray and immunohistochemistry, we evaluated BRG1 staining in 437 breast cancer specimens and investigated its role in breast cancer cell proliferation, migration and invasion. Our Kaplan-Meier survival curves showed that high BRG1 expression is inversely correlated with both overall (P = 0.000) and disease-specific (P = 0.000) 5-year patient survival. Furthermore, we found that knockdown of BRG1 by RNA interference markedly inhibits cell proliferation and causes cessation of cell cycle. This reduced cell proliferation is due to G1 phase arrest as cyclin D1 and cyclin E are diminished whereas p27 is upregulated. Moreover, BRG1 depletion induces the expression of TIMP-2 but reduces MMP-2, thereby inhibiting the ability of cells to migrate and to invade. These results highlight the importance of BRG1 in breast cancer pathogenesis and BRG1 may serve as a prognostic marker as well as a potentially selective therapeutic target.

/pdf/brg1-is-a-prognostic-marker-and-potential-therapeutic-target-3vhe7kggqg.pdf

BRG1 is a prognostic marker and potential therapeutic target in human breast cancer.

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Molecular Mechanisms Underlying the Analgesic Property of Intrathecal Dexmedetomidine and Its Neurotoxicity Evaluation: An In Vivo and In Vitro Experimental Study

Brain-Derived Neurotrophic Factor in the Mesolimbic Reward Circuitry Mediates Nociception in Chronic Neuropathic Pain.

BRG1 is a prognostic marker and potential therapeutic target in human breast cancer.