Dichotomy of Tyrosine Hydroxylase and Dopamine Regulation between Somatodendritic and Terminal Field Areas of Nigrostriatal and Mesoaccumbens Pathways

Measures of dopamine-regulating proteins in somatodendritic regions are often used only as static indicators of neuron viability, overlooking the possible impact of somatodendritic dopamine (DA) signaling on behavior and the potential autonomy of DA regulation between somatodendritic and terminal field compartments. DA reuptake capacity is less in somatodendritic regions, possibly placing a greater burden on de novo DA biosynthesis within this compartment to maintain DA signaling. Therefore, regulation of tyrosine hydroxylase (TH) activity may be particularly critical for somatodendritic DA signaling. Phosphorylation of TH at ser31 or ser40 can increase activity, but their impact on L-DOPA biosynthesis in vivo is unknown. Thus, determining their relationship with L-DOPA tissue content could reveal a mechanism by which DA signaling is normally maintained. In Brown-Norway Fischer 344 F1 hybrid rats, we quantified TH phosphorylation versus L-DOPA accumulation. After inhibition of aromatic acid decarboxylase, L-DOPA tissue content per recovered TH protein was greatest in NAc, matched by differences in ser31, but not ser40, phosphorylation. The L-DOPA per catecholamine and DA turnover ratios were significantly greater in SN and VTA, suggesting greater reliance on de novo DA biosynthesis therein. These compartmental differences reflected an overall autonomy of DA regulation, as seen by decreased DA content in SN and VTA, but not in striatum or NAc, following short-term DA biosynthesis inhibition from local infusion of the TH inhibitor α-methyl-p-tyrosine, as well as in the long-term process of aging. Such data suggest ser31 phosphorylation plays a significant role in regulating TH activity in vivo, particularly in somatodendritic regions, which may have a greater reliance on de novo DA biosynthesis. Thus, to the extent that somatodendritic DA release affects behavior, TH regulation in the midbrain may be critical for DA bioavailability to influence behavior

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

Reversal of dopamine inhibition of dopaminergic neurons of the ventral tegmental area is mediated by protein kinase C

Adaptation of putative dopaminergic (pDA) neurons in the ventral tegmental area (VTA) to drugs of abuse may alter information processing related to reward and reinforcement and is a key factor in the development of addiction. We have demonstrated that prolonged increases in the concentration of dopamine (DA) result in a time-dependent decrease in sensitivity of pDA neurons to DA, which we termed dopamine inhibition reversal (DIR). In the present study, we used extracellular recordings to examine factors mediating DIR. A 40 min administration of DA (2.5-10 μM), but not the DA D2 receptor agonist quinpirole (50-200 nM), resulted in inhibition of neuronal firing followed by DIR. In the presence of 100 nM cocaine, inhibition followed by DIR was seen with much lower DA concentrations. Reversal of quinpirole inhibition could be induced by an activator of protein kinase C, but not of protein kinase A. Inhibitors of protein kinase C or phospholipase C blocked the development of DIR. Disruption of intracellular calcium release also prevented DIR. Reduction of extracellular calcium or inhibition of store-operated calcium entry blocked DIR, but the L-type calcium channel blocker nifedipine did not. DIR was age-dependent and not seen in pDA VTA neurons from rat pups younger than 15 days postnatal. Our data indicate that DIR is mediated by protein kinase C, and implicate a conventional protein kinase C. This characterization of DIR gives insight into the regulation of autoinhibition of pDA VTA neurons, and the resulting long-term alteration in information processing related to reward and reinforcement

Effectiveness and safety of polymyxin B for the treatment of infections caused by extensively drug-resistant Gram-negative bacteria in Thailand

Thundon Ngamprasertchai,1 Adhiratha Boonyasiri,2 Lantharita Charoenpong,3 Sireethorn Nimitvilai,4 Narisorn Lorchirachoonkul,5 Luksame Wattanamongkonsil,2 Visanu Thamlikitkul6 1Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; 2Department of Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand; 3Division of Medicine, Chaophraya Yommarat Hospital, Suphanburi, Thailand; 4Division of Medicine, Nakhornpathom Hospital, Nakhornpathom, Thailand; 5Division of Medicine, Ratchaburi Hospital, Ratchaburi, Thailand; 6Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand Background: Colistimethate sodium (colistin) has been used in the treatment of infections caused by extensively drug-resistant (XDR) Gram-negative bacteria in Thailand over the past decade, with a mortality rate of 50% and a nephrotoxicity rate of 40%. Polymyxin B has not been available in Thailand. We conducted a Phase II clinical study to determine the effectiveness and safety of polymyxin B, compared with colistin, for the treatment of XDR Gram-negative bacterial infections in Thai patients.Methods: A total of 73 adult patients hospitalized at four participating tertiary care hospitals from January 2015 to December 2015 who had infections caused by XDR Gram-negative bacteria and had to receive colistin were enrolled in the study. Polymyxin B (100 mg/day) was administered intravenously every 12 hours for 7–14 days.Results: Most of the patients were older males with comorbidities who had received antibiotics, particularly carbapenems, prior to receiving polymyxin B. More than half of the patients had pneumonia, and 51.5% of the infections were caused by XDR Acinetobacter baumannii, which was susceptible to colistin. Good clinical responses at the end of treatment were observed in 78.1% of cases, the overall 28-day mortality rate from all causes was 28.7%, the microbiological clearance of the targeted bacteria after therapy was 56.2% and nephrotoxicity occurred in 24.7% of cases. Neurotoxicity relating to reversible numbness was observed in two cases.Conclusion: Polymyxin B seems to be effective and safe for the treatment of XDR Gram-negative bacterial infections. Polymyxin B should be considered as an alternative to colistin for treatment of infections caused by XDR Gram-negative bacteria in Thai adult patients, especially those at risk of nephrotoxicity. Keywords: mortality, acute kidney injury, Acinetobacter baumanni

Suppression of Gq function using intra-pipette delivery of shRNA during extracellular recording in the ventral tegmental area

Selective suppression of protein function in the brain can be achieved using specific silencing RNAs administered in vivo. A viral delivery system is often employed to transfect neurons with small hairpin RNA (shRNA) directed against specific proteins, and intervals of several days are allowed between microinjection of the shRNA-containing virus into the brain and experiments to assess suppression of gene function. Here we report studies using extracellular recording of dopaminergic neurons of the ventral tegmental area (DA VTA neurons) recorded in brain slices in which lentivirus containing shRNA directed against Gq was included in the recording pipette, and suppression of Gq-related function was observed within the time frame of the recording. The action of neurotensin (NT) is associated with activation of Gq, and the firing rate of DA VTA neurons is increased by NT. With shRNA directed against Gq in the pipette, there was a significant reduction of NT excitation within 2h. Likewise, time-dependent dopamine desensitization, which we have hypothesized to be Gq-dependent, was not observed when shRNA directed against Gq was present in the pipette and dopamine was tested 2h after initiation of recording. As the time interval (2h) is relatively short, we tested whether blockade of protein synthesis with cycloheximide delivered via the recording pipette would alter Gq-linked responses similarly. Both NT-induced excitation and dopamine desensitization were inhibited in the presence of cycloheximide. Inclusion of shRNA in the recording pipette may be an efficient and selective way to dampen responses linked to Gq, and, more generally, the use of lentiviral-packaged shRNA in the recording pipette is a means to produce selective inhibition of the function of specific proteins in experiments

Oral sitafloxacin vs intravenous ceftriaxone followed by oral cefdinir for acute pyelonephritis and complicated urinary tract infection: a randomized controlled trial

Bannakij Lojanapiwat,1 Sireethorn Nimitvilai,2 Manit Bamroongya,3 SupunNee Jirajariyavej,4 Chirawat Tiradechavat,5 Aumnat Malithong,6 Chagkrapan Predanon,7 Dan Tanphaichitra,8 Boonlert Lertsupphakul9 1Department of Surgery, Maharaj Nakorn Chiang Mai Hospital, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; 2Department of Internal Medicine, Nakhon Pathom Hospital, Nakhon Pathom, Thailand; 3Department of Surgery, Buddasothorn Hospital, Chachoengsao, Thailand; 4Department of Medicine, Taksin Hospital, Bangkok, Thailand; 5Department of Surgery, Udon Thani Hospital, Udon Thani, Thailand; 6Department of Medicine, BMA General Hospital, Bangkok, Thailand; 7Department of Surgery, Khon Kaen Hospital, Khon Kaen, Thailand; 8Department of Internal Medicine, Anandamahidol Hospital, Lopburi, Thailand; 9Department of Surgery, Maharaj Nakorn Si Thammarat Hospital, Nakhon Si Thammarat, Thailand Background: The conventional antibiotic regimen for community-acquired upper urinary tract infections with moderate severity in Thailand is parenteral ceftriaxone (CTRX) for several days followed by oral cephalosporin for 7–14 days. The aim of this study was to compare the efficacy and safety of oral sitafloxacin (STFX) with that of intravenous CTRX followed by oral cefdinir (CFDN) for the therapy of acute pyelonephritis (APN) and complicated urinary tract infection (cUTI).Methods: This open-label, randomized, controlled, noninferiority clinical trial included patients from nine centers across Thailand. Adult patients with APN or cUTI were randomly assigned to receive 100 mg of oral STFX twice daily for 7–14 days, or 2 g of intravenous CTRX for several days followed by 100 mg of oral CFDN three times per day for another 4–12 days.Results: A total of 289 adult patients with APN or cUTI (141 in the STFX group and 148 in the CTRX/CFDN group) were included in the intent-to-treat (ITT) analysis, and 211 patients (108 in the STFX group and 103 in the CTRX/CFDN group) were included in the per-protocol (PP) analysis. The baseline characteristics of patients in both groups were comparable. The causative pathogen in most patients with APN or cUTI was Escherichia coli. The clinical success rates at the end of treatment revealed the STFX regimen to be noninferior to the CTRX/CFDN regimen (86.6% vs 83.8% for ITT analysis and 97.2% vs 99.0% for PP analysis, respectively). Adverse events with mild-to-moderate severity were similar between groups.Conclusion: Oral STFX is noninferior to intravenous CTRX followed by oral CFDN in adult patients with APN and cUTI. Lower rates of resistance compared to CTRX and/or CFDN and oral administration suggest STFX as a more attractive treatment option in this patient population. Keywords: acute pyelonephritis, complicated urinary tract infection, sitafloxacin, ceftriaxone, cefdini

Reversal of Prolonged Dopamine Inhibition of Dopaminergic Neurons of the Ventral Tegmental Area

Drug abuse-induced plasticity of putative dopaminergic (pDAergic) ventral tegmental area (VTA) neurons may play an important role in changes in the mesocorticolimbic system that lead to the development of addiction. In the present study, extracellular recordings were used to examine time-dependent effects of dopamine (DA) on pDAergic VTA neurons in rat brain slices. Administration of DA (2.5–10 μM) for 40 min resulted in inhibition followed by partial or full reversal of that inhibition. The reduced sensitivity to DA inhibition lasted 30 to 90 min after washout of the long-term dopamine administration. The inhibition reversal was not observed with 40-min administration of the D2 agonist quinpirole (25–200 nM), so this phenomenon was not the result of desensitization induced solely by stimulation of D2 DA receptors. Inhibition reversal could be observed with the coapplication of quinpirole and the D1/D5 agonist SKF38393 [(±)-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol hydrobromide], suggesting a D1/D5 mechanism for the reversal. Furthermore, D1/D5 antagonists, given in the presence of prolonged DA exposure, prevented the inhibition reversal. Application of 3 μM quinpirole caused desensitization to low quinpirole concentrations that was blocked by a D1/D5 antagonist. These data suggest that coactivation of D1/D5 receptors and D2 receptors in the VTA results in desensitization of autoinhibitory D2 receptors. Prolonged increases in pDAergic tone in the VTA that may occur in vivo with drugs of abuse could reduce the regulation of firing by D2 dopamine receptor activation, producing long-term alteration in information processing related to reward and reinforcement