The effects of phosphodiesterase (PDE) 4 inhibitors on gene expression changes in BEAS-2B human airway epithelial cells are reported and discussed in relation to the mechanism(s) of action of roflumilast in chronic obstructive pulmonary disease (COPD). Microarray-based gene expression profiling failed to identify mRNA transcripts that were differentially regulated by the PDE4 inhibitor 6-[3-(dimethylcarbamoyl)benzenesulphonyl]-4-[(3-methoxyphenyl)amino]-8-methylquinoline-3-carboxamide (GSK 256066) after 1, 2, 6, or 18 hours of exposure. However, real-time polymerase chain reaction analysis revealed that GSK 256066 was a weak stimulus, and the negative microarray results reflected low statistical power due to small sample sizes. Furthermore, GSK 256066, roflumilast, and its biologically active metabolite roflumilast N-oxide generally potentiated gene expression changes produced by the long-acting β2-adrenoceptor agonists (LABAs) salmeterol, indacaterol, and formoterol. Many of these genes encode proteins with antiviral, anti-inflammatory, and antibacterial activities that could contribute to the clinical efficacy of roflumilast in COPD. RNA-sequencing experiments established that the sensitivity of genes to salmeterol varied by ∼7.5-fold. Consequently, the degree to which a PDE4 inhibitor potentiated the effect of a given concentration of LABA was gene-dependent. Operational model fitting of concentration-response curve data from cells subjected to fractional, β2-adrenoceptor inactivation determined that PDE4 inhibition increased the potency and doubled the efficacy of LABAs. Thus, adding roflumilast to standard triple therapy, as COPD guidelines recommend, may have clinical relevance, especially in target tissues where LABAs behave as partial agonists. Collectively, these results suggest that the genomic impact of roflumilast, including its ability to augment LABA-induced gene expression changes, may contribute to its therapeutic activity in COPD.
The basic flow of ions into or out of a cell has the potential to greatly impact the propagation of electrical signals. This chapter focuses on the electrical properties of ions as they move through a conductive medium and how this movement generates potentials and currents. At the conclusion of this chapter, the reader is expected to have a better understanding of the driving forces that evoke electrochemical gradients and how these driving forces impact extracellular (e.g., field potentialsField potentials) and intracellular recordings. Lastly, given that electrophysiological measurements take into account electrical activity, this chapter concludes with a description of capacitanceCapacitance and how it affects the electrical circuit.
There are different types of synapses and receptors that regulate fast and slow synaptic currents. This chapter discusses two classes of synapses (e.g., chemical and electrical) and the receptors that populate these synapses including ionotropic receptors, metabotropic receptors, and gap junctions. We discuss the speed with which these receptors mediate or regulate ionic currents with the purpose of supplying the reader with a general idea of current kinetics. In addition, we include technical considerations when measuring fast and slow synaptic currents as well as, in some cases, the physiological relevance of current kinetics (see Chap. 17 for more details regarding ionotropic receptor kinetics).
Abstract Pain experience can change the central processing of nociceptive inputs, resulting in persistent allodynia and hyperalgesia. However, the underlying circuit mechanisms remain underexplored. Here, we focus on pain-induced remodeling of the projection from the mediodorsal thalamus (MD) to the anterior cingulate cortex (ACC), a projection that relays spinal nociceptive input for central processing. Using optogenetics combined with slice electrophysiology, we detected in male mice that 7 days of chronic constriction injury (CCI; achieved by loose ligation of the sciatic nerve) generated AMPA receptor (AMPAR)-silent glutamatergic synapses within the contralateral MD-to-ACC projection. AMPAR-silent synapses are typically GluN2B-enriched nascent glutamatergic synapses that mediate the initial formation of neural circuits during early development. During development, some silent synapses mature and become “unsilenced” by recruiting and stabilizing AMPARs, consolidating and strengthening the newly formed circuits. Consistent with these synaptogenic features, pain-induced generation of silent synapses was accompanied by increased densities of immature dendritic spines in ACC neurons and increased synaptic weight of GluN2B-containing NMDA receptors (NMDARs) in the MD-to-ACC projection. After prolonged (∼30 days) CCI, injury-generated silent synapses declined to low levels, which likely resulted from a synaptic maturation process that strengthens AMPAR-mediated MD-to-ACC transmission. Consistent with this hypothesis, viral-mediated knockdown of GluN2B in ACC neurons, which prevented pain-induced generation of silent synapses and silent synapse-mediated strengthening of MD-to-ACC projection after prolonged CCI, prevented the development of allodynia. Taken together, our results depict a silent synapse-mediated mechanism through which key supraspinal neural circuits that regulate pain sensitivity are remodeled to induce allodynia and hyperalgesia.
Background: Parenteral penicillin is the first-line regimen for treating syphilis. However, allergic reactions and poor drug tolerance still present challenging problems with respect to use of this antibiotic.Methods: By searching PubMed and Embase databases, studies concerning ceftriaxone, erythromycin, minocycline, tetracycline, doxycycline, and penicillin for syphilis treatment were selected and included in eligible randomized controlled trials (RCT) and observational studies. A systematic review and network meta-analysis were performed. This study aimed to evaluate the efficacy and safety of ceftriaxone, erythromycin, minocycline, tetracycline, and doxycycline for syphilis treatment when compared with penicillin to determine which antibiotic could be a better substitute for penicillin. The Cochrane Handbook for Systematic Reviews of Interventions to assess the RCTs’ risk of bias and a modified Newcastle–Ottawa Scale (NOS) to assess the quality of each cohort study.Findings: This study included 17 articles, including three RCTs and 14 observational studies, involving 4485 syphilis patients. Estimated risk ratio (RRs) and 95% confidence interval (CIs) were used to compare their serological response rates. At the 6- and 12-month follow-ups, the serological response rate was compared by direct meta-analysis and network meta-analysis (NMA). Based on direct meta-analysis, the serological response rates at 3- and 24-month follow-ups were compared. Only three of the included studies reported drug safety. Due to the lack of reported data, this study only made a qualitative analysis of adverse drug reactions associated with syphilis treatment. The results of NMA indicated that the serological reaction rate of ceftriaxone was higher than that of penicillin (RR = 1·17; 95% CI 1·06–1·28) at the 6-month follow-up. Interpretation: In terms of serological response rate, ceftriaxone is as effective as penicillin for syphilis treatment. When compared with ceftriaxone, erythromycin, minocycline, tetracycline, and doxycycline, ceftriaxone appears to be a better alternative to penicillin.Funding Information: This study was supported by the National Natural Science Foundation of China ( No. 32060180, 82160304, 81560596, 81860644, and 31560051 ), Natural Foundation of Yunnan Province (2017FE467-001, 2019FE001-002).Declaration of Interests: We declare no competing interests.
Electrophysiological measurements of single synapses are challenging given the size of a single synapse relative to a patch pipette. In addition, one has to take into account the limitations of microscopes in that they need to provide acceptable visualization of a single synapse for patching. However, despite these limitations, researchers have successfully measured single synaptic function along dendrites. The purpose of this chapter is to introduce the techniques that can be implemented to measure single synaptic function. Included in this chapter are such techniques as localized perfusion, localized electrical stimulationElectrical stimulation, photostimulation, and imagingImaging. These techniques are designed with the assumption that multiple excitatory synapses do not contact a single spine but rather only one synapse per spine. Whereas this assumption is supported by some empirical data (Schikorski, Stevens, J Neurosci 17(15):5858–5867, 1997), other data suggest otherwise (Toni et al, Nature 402(6760):421–425, 1999), meaning that a complete understanding of the anatomical region is necessary before beginning single synapse experiments.
High rates of relapse to drug use during abstinence is a defining feature of human drug addiction. This clinical scenario has been studied at the preclinical level using different animal models in which relapse to drug seeking is assessed after cessation of operant drug self-administration in rodents and monkeys. In our Society for Neuroscience (SFN) session entitled “Circuit and Synaptic Plasticity Mechanisms of Drug Relapse,” we will discuss new developments of our understanding of circuits and synaptic plasticity mechanisms of drug relapse from studies combining established and novel animal models with state-of-the-art cellular, electrophysiology, anatomical, chemogenetic, and optogenetic methods. We will also discuss the translational implications of these new developments. In the mini-review that introduces our SFN session, we summarize results from our laboratories on behavioral, cellular, and circuit mechanisms of drug relapse within the context of our session.
Synaptic plasticity in the mesolimbic dopamine (DA) system is thought to contribute to the neural adaptations that mediate behavioral sensitization, a model for core aspects of addiction. Recently, it has been demonstrated that multiple classes of drugs of abuse, as well as acute stress, enhance strength at excitatory synapses on midbrain DA neurons. Here, we show that both the cocaine- and stress-induced synaptic enhancement involves an up-regulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors. This enhancement requires the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit GluRA as evidenced by its absence in mice lacking this subunit. The cocaine-elicited, but not the stress-elicited, synaptic potentiation in DA neurons was blocked by a D1-like receptor antagonist, indicating that the in vivo triggering mechanisms differ for these forms of experience-dependent synaptic modification. Surprisingly, behavioral sensitization to cocaine was elicited in GluRA(-/-) mice, indicating that potentiation of excitatory synaptic transmission in DA neurons is not necessary for this form of behavioral plasticity. However, GluRA(-/-) mice did not exhibit a conditioned locomotor response when placed in a context previously paired with cocaine, nor did they exhibit conditioned place preference in response to cocaine. We suggest that the drug-induced enhancement of excitatory synaptic transmission in midbrain DA neurons, although not required for behavioral sensitization per se, may contribute to the attribution of incentive value to drug-associated cues.
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