Increase in CFC-11 emissions from eastern China based on atmospheric observations.

The recovery of the stratospheric ozone layer relies on the continued decline in the atmospheric concentrations of ozone-depleting gases such as chlorofluorocarbons1. The atmospheric concentration of trichlorofluoromethane (CFC-11), the second-most abundant chlorofluorocarbon, has declined substantially since the mid-1990s2. A recently reported slowdown in the decline of the atmospheric concentration of CFC-11 after 2012, however, suggests that global emissions have increased3,4. A concurrent increase in CFC-11 emissions from eastern Asia contributes to the global emission increase, but the location and magnitude of this regional source are unknown3. Here, using high-frequency atmospheric observations from Gosan, South Korea, and Hateruma, Japan, together with global monitoring data and atmospheric chemical transport model simulations, we investigate regional CFC-11 emissions from eastern Asia. We show that emissions from eastern mainland China are 7.0 ± 3.0 (±1 standard deviation) gigagrams per year higher in 2014-2017 than in 2008-2012, and that the increase in emissions arises primarily around the northeastern provinces of Shandong and Hebei. This increase accounts for a substantial fraction (at least 40 to 60 per cent) of the global rise in CFC-11 emissions. We find no evidence for a significant increase in CFC-11 emissions from any other eastern Asian countries or other regions of the world where there are available data for the detection of regional emissions. The attribution of any remaining fraction of the global CFC-11 emission rise to other regions is limited by the sparsity of long-term measurements of sufficient frequency near potentially emissive regions. Several considerations suggest that the increase in CFC-11 emissions from eastern mainland China is likely to be the result of new production and use, which is inconsistent with the Montreal Protocol agreement to phase out global chlorofluorocarbon production by 2010.

Eosinophil-derived TGFß1 controls the new bone formation in chronic rhinosinusitis with nasal polyps

BACKGROUND: Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by chronic eosinophilic inflammation and new bone formation (NBF). These processes may be associated with each other in the pathogenesis and influence the severity and prognosis of the disease. However, it is still unclear how eosinophilic inflammation is involved in the NBF. METHODOLOGY: Sinus bone cells were isolated from ethmoid bone tissues of patients with CRSwNP and controls. Transforming growth factor beta 1 (TGFß1) and alkaline phosphatase (ALP) expression in sinus bone cells was determined using quantitative RT-PCR, immunoblotting, and immunohistochemistry. The co-localization of TGFß1 with eosinophils was assessed by immunofluorescence staining. Sinus bone cells were co-cultured with eosinophils (Eol-1 cell line), which were differentiated with butyrate, to measure the osteoblast differentiation activity of sinus bone cells. RESULTS: TGFß1 expression was increased in sinus bone tissues and correlated with CT scores in CRSwNP. TGFß1 was also increased in the submucosa of CRSwNP and co-localized predominantly with eosinophils compared with neutrophils Differentiated Eol-1 cells-derived TGFß1 increased ALP expression in sinus bone cells. Treatment with a TGFß inhibitor attenuated TGFß1-induced ALP expression and staining in sinus bone cells of CRSwNP, leading to loss of bone formation. CONCLUSIONS: Eosinophil-derived TGFß1 was enriched in the submucosa of CRSwNP, which induced ALP expression in sinus bone cells and NBF. Therefore, eosinophil-derived TGFß1 may mediate aberrant bone remodeling in CRSwNP.

Clinical significance of nutritional risk screening tool for hospitalised children with acute burn injuries: a cross-sectional study.

BACKGROUND: We assessed the nutritional risks among children hospitalised with acute burn injuries and their associated clinical outcomes using three nutritional risk screening (NRS) tools: Screening Tool for Risk of Impaired Nutritional Status and Growth (STRONGKIDS ), Pediatric Yorkhill Malnutrition Score (PYMS) and Screening Tool for the Assessment for Malnutrition in Pediatrics (STAMP). METHODS: This prospective cross-sectional study was conducted from October 2015 to November 2016, in a regional burn centre. Patients were screened by two independent observers, using the three NRS tools. RESULTS: A total of 100 children aged 3 months to 16.5 years were included. STRONGKIDS identified 16% of patients as having high risk, with being identified 45% by PYMS and 44% by STAMP. After adjustment for confounding factors in multivariate regression analysis, patients in the high-risk group had significantly longer median (SD) lengths of stay [medium versus high risk: STRONGKIDS , 9.5 (6.6) versus 15.0 (24.2) days; PYMS, 8.5 (4.4) versus 13.0 (16.1) days; STAMP, 9.0 (5.7) versus 11.0 (17.4) days] and greater median (SD) weight loss [medium versus high risk: STRONGKIDS, 0.15 (0.8) versus -0.35 (0.8) kg; STAMP, 0.5 (0.7) versus 0 (0.1) kg] than patients in the medium-risk group (P < 0.05). The strengths of agreement in the nutritional risk classification between the two observers were good (κ for STRONGKIDS = 0.61; PYMS = 0.79; STAMP = 0.75) (P < 0.01). CONCLUSIONS: The STRONGKIDS , PYMS and STAMP tools could be useful and practical for determining which hospitalised children with acute burn injuries will need additional nutritional intervention.

Meal patterns across ten European countries - results from the European Prospective Investigation into Cancer and Nutrition (EPIC) calibration study.

OBJECTIVE: To characterize meal patterns across ten European countries participating in the European Prospective Investigation into Cancer and Nutrition (EPIC) calibration study. DESIGN: Cross-sectional study utilizing dietary data collected through a standardized 24 h diet recall during 1995-2000. Eleven predefined intake occasions across a 24 h period were assessed during the interview. In the present descriptive report, meal patterns were analysed in terms of daily number of intake occasions, the proportion reporting each intake occasion and the energy contributions from each intake occasion. SETTING: Twenty-seven centres across ten European countries. SUBJECTS: Women (64 %) and men (36 %) aged 35-74 years (n 36 020). RESULTS: Pronounced differences in meal patterns emerged both across centres within the same country and across different countries, with a trend for fewer intake occasions per day in Mediterranean countries compared with central and northern Europe. Differences were also found for daily energy intake provided by lunch, with 38-43 % for women and 41-45 % for men within Mediterranean countries compared with 16-27 % for women and 20-26 % for men in central and northern European countries. Likewise, a south-north gradient was found for daily energy intake from snacks, with 13-20 % (women) and 10-17 % (men) in Mediterranean countries compared with 24-34 % (women) and 23-35 % (men) in central/northern Europe. CONCLUSIONS: We found distinct differences in meal patterns with marked diversity for intake frequency and lunch and snack consumption between Mediterranean and central/northern European countries. Monitoring of meal patterns across various cultures and populations could provide critical context to the research efforts to characterize relationships between dietary intake and health.

Clinical characteristics of Korean patients with filaggrin-related atopic dermatitis.

BACKGROUND: Filaggrin is a key protein involved in skin barrier function. Mutations in the gene encoding filaggrin (FLG) have been identified as the cause of ichthyosis vulgaris and have been shown to be major predisposing factors for atopic dermatitis (AD). AIM: To investigative the clinical characteristics of patients with AD with FLG mutations and determine the differences between patients with AD with and without FLG mutations. METHODS: We identified FLG mutations in patients with AD by complete sequencing and SNaPshot methods, and then analysed the data on clinical characteristics from questionnaire responses. RESULTS: We found that earlier age of AD onset (P < 0.05), tendency to respiratory atopy (P = 0.03), more severe clinical characteristics of AD (higher Eczema Area and Severity Index, P = 0.02) and decrease in skin hydration (P = 0.04) were associated with FLG-related AD. CONCLUSION: Our data demonstrate that FLG mutations are indicators of a poor prognosis in AD, and are predisposing factors that exist in early infancy and persist into adulthood.

TLR2-dependent amelioration of allergic airway inflammation by parasitic nematode type II MIF in mice.

In our previous studies, the recombinant type II macrophage migration inhibitory factor homologue (rAs-MIF) secreted from Anisakis simplex suppressed experimental inflammation mouse model through IL-10 production and CD4(+)CD25(+)Foxp3(+) T-cell recruitment. Also, TLR2 gene expression was significantly increased following rAs-MIF treatment. To know the relation between TLR2 and amelioration mechanisms of rAs-MIF, we induced allergic airway inflammation by ovalbumin and alum with or without rAs-MIF under TLR2 blocking systems [anti-TLR2-specific antibody (α-mTLR2 Ab) treatment and using TLR2 knockout mice]. As a result, the amelioration effects of rAs-MIF in allergic airway inflammation model (diminished inflammation and Th2 response in the lung, increased IL-10 secretion, CD4(+)CD25(+)Foxp3(+) T-cell recruitment) were diminished under two of the TLR2 blocking model. The expression of TLR2 on the surface of lung epithelial cell was significantly elevated by rAs-MIF treatment or Pam3CSK (TLR2-specific agonist) treatment, but they might have some competition effect on the elevation of TLR2 expression. In addition, the elevation of IL-10 gene expression by rAs-MIF treatment was significantly inhibited by α-mTLR2 Ab or Pam3CSK pretreatment. In conclusion, anti-inflammatory effects of the rAs-MIF on OVA-induced allergic airway inflammation might be closely related to TLR2.

Rebamipide attenuates pain severity and cartilage degeneration in a rat model of osteoarthritis by downregulating oxidative damage and catabolic activity in chondrocytes.

OBJECTIVE: The objectives were to investigate the in vivo effects of treatment with rebamipide on pain severity and cartilage degeneration in an experimental model of rat osteoarthritis (OA) and to explore its mode of action. MATERIALS AND METHODS: OA was induced in rats by intra-articular injection of monosodium iodoacetate (MIA). Oral administration of rebamipide was initiated on the day of MIA injection, 3 or 7 days after. Limb nociception was assessed by measuring the paw withdrawal latency and threshold. We analyzed the samples macroscopically and histomorphologically, and used immunohistochemistry to investigate the expression of matrix metalloproteinase-13 (MMP-13), interleukin-1ß (IL-1ß), hypoxia-inducible factor-2α (HIF-2α), inducible nitric oxide synthase (iNOS), and nitrotyrosine in knee joints. Real-time quantitative reverse transcription-polymerase chain reaction was used to quantify the mRNA for catabolic and anticatabolic factors in human OA chondrocytes. RESULTS: Rebamipide showed an antinociceptive property and attenuated cartilage degeneration. Rebamipide reduced the expression of MMP-13, IL-1ß, HIF-2α, iNOS, and nitrotyrosine in OA cartilage in a dose-dependent manner. Nitrotyrosine expression in the subchondral bone region was decreased in the rebamipide-treated joints. mRNA expression of MMP-1, -3, and -13, and ADAMTS5 was attenuated in IL-1ß-stimulated human OA chondrocytes. By contrast, rebamipide induced the mRNA expression of tissue inhibitor of metalloproteinase-1 and -3. CONCLUSION: The results show the inhibitory effects of rebamipide on pain production and cartilage degeneration in experimentally induced OA. The suppression of oxidative damage and the restoration of extracellular matrix homeostasis of articular chondrocyte suggest that rebamipide is a potential therapeutic strategy for OA.

Serotonin induces melanogenesis via serotonin receptor 2A.

BACKGROUND: Serotonin (5-hydroxytryptamine, 5-HT) levels are increased by light exposure but the role and mechanism of 5-HT in the pigmentation of skin cells are unclear. OBJECTIVES: To clarify the effect of 5-HT on melanogenesis and to determine the 5-HT receptor subtype involved. METHODS: B16F10, SK-MEL-2 and Melan-A cells were cultured in Dulbecco's modified Eagle's medium with low fetal bovine serum. The three cell lines were treated with various concentrations of 5-HT, and 5-HT receptor agonists and antagonists. The involvement of the 5-HT receptor 2A (5-HTR2A) was examined by gene silencing and use of 5-HTR2A antagonists. RESULTS: 5-HT and the 5-HTR2A agonist, DOI, increased melanogenesis in the three cell lines. These increased events were suppressed by 5-HTR2A antagonists or gene silencing of the HTR2A gene. CONCLUSIONS: 5-HTR2A is involved in melanogenesis. These findings highlight the role of 5-HT and suggest new ways of controlling melanogenesis.

Open label, three period, single sequence, study of 5, 25, 50 mg sertraline pharmacokinetics in healthy male Korean volunteers.

BACKGROUND: Sertraline is a naphthalenamine derivative which has the effect of selective serotonin reuptake inhibition. It has been used for major depression, and obsessive compulsive disorder. This study was performed to evaluate the pharmacokinetic (PK) characteristics after the administration of low dose sertraline for the purpose of exploring an application of microdosing methods in PK studies. METHODS: An open-label, three-period, single-sequence, dose-escalation study was performed in 6 healthy Korean male volunteers. Subjects were administered a single dose of 5 mg, 25 mg and 50 mg sertraline orally in each period, with 1 week washouts between periods. Blood samples were obtained up to 96 h after drug administration. Plasma concentrations were determined using high performance liquid chromatography-tandem mass spectrometry. PK parameters of sertraline were analyzed using non-compartmental methods. RESULTS: A total of 6 subjects completed the study. After the administration of sertraline at 5 mg, 25 mg and 50 mg, the median tmax were 6.0, 6.0 and 4.0 h and the mean (SD) elimination half-lives were 31.9 (6.5), 27.2 (6.7) and 28.0 (6.6) h, respectively. The AUC and Cmax increased dose-dependently. The dose-normalized mean (SD) AUC and Cmax were different in each dosing group (p < 0.01) with 2.0 (0.8), 5.3 (1.2) and 6.0 (1.9) mg × hr/l/mg in the 5 mg, 25 mg and 50 mg groups for dose-normalized AUC, and 0.07 (0.01), 0.18 (0.05) and 0.21 (0.08) mg/l/mg in the 5 mg, 25 mg and 50 mg groups for dose-normalized Cmax, respectively, which indicates a lack of dose proportionality. CONCLUSION: A lack of dose proportional properties was shown in the 5 mg dose relative to the 25 mg and 50 mg doses of sertraline. This shows that the PK parameters for low-dose sertraline could be different from those in clinical concentrations.

Primary sequence and heterologous expression of nuclear pore glycoprotein p62.

The major nuclear pore protein p62 is modified by O-linked N-acetylglucosamine and functions in nuclear transport. We have cloned, sequenced, and expressed the full-length rat p62 cDNA. The rat p62 mRNA is 2,941 nucleotides long and encodes a protein of 525 amino acids containing 30% serine and threonine residues. The amino acid sequence near the amino-terminus contains unique tetrapeptide repeats while the carboxy-terminus consists of a series of predicted alpha-helical regions with hydrophobic heptad repeats. Heterologous expression of rat p62 in African Green Monkey Kidney COS-1 cells and CV-1 cells was detected using a species-specific antipeptide serum. When transiently expressed in COS-1 cells, rat p62 binds wheat germ agglutinin and concentrates at the spindle poles during mitosis. In CV-1 cells cotransfected with rat p62 cDNA and SV40 viral DNA, rat p62 associates with the nuclear membrane without interfering with the nuclear transport of SV40 large T antigen. The ability to express p62 in tissue culture cells will facilitate analysis of the role of this pore protein in nuclear transport.

Steroid-sparing effects of pentoxifylline in pulmonary sarcoidosis.

BACKGROUND: Agents that target pro-inflammatory cytokines may be useful in pulmonary sarcoidosis. OBJECTIVE: To determine effectiveness of a non-selective cyclic nucleotide phosphodiesterase (PDE) inhibitor, pentoxifylline (POF). DESIGN: Randomized, double-blind, placebo-controlled trial, SETTING: Clinical Research Center, National Institutes of Health. PATIENTS: 27 patients with biopsy-confirmed pulmonary sarcoidosis receiving prednisone. INTERVENTION: Placebo or POF (1200-2000 mg/day) for 10 months, as prednisone was tapered. MEASUREMENTS: Primary endpoints: sustained improvement in two or more pulmonary function parameters, or a combination of one pulmonary function parameter and dyspnea. RESULTS: Except for one patient, primary endpoints were not reached in POF-treated patients. Therefore, a post hoc analysis was performed. The observed relative risk reduction for flares associated with POF treatment was 54.9% (95% CI 0.21, 0.89) and the absolute risk reduction was 50.6% (95% CI 0.22, 0.80). Compared to placebo treatment, in the POF group, the mean prednisone dose was lower at 8 and 10 months (p = 0.007 and 0.01 respectively), and there was a trend towards less prednisone usage over the entire study period (p = 0.053), as determined by cumulative change analysis. CONCLUSIONS: Although our exploratory post hoc analysis suggested that POF reduced flares and had steroid-sparing effects, given the study limitations, definitive conclusions cannot be drawn regarding the efficacy of POF in pulmonary sarcoidosis. In addition, gastrointestinal side-effects, at the doses used, would seem to limit the use of POF in treating pulmonary sarcoidosis. Overall, however, this trial may provide a basis for using more specific, better-tolerated, PDE inhibitors in future clinical trials.

Chemical evidence of inter-hemispheric air mass intrusion into the Northern Hemisphere mid-latitudes.

The East Asian Summer Monsoon driven by temperature and moisture gradients between the Asian continent and the Pacific Ocean, leads to approximately 50% of the annual rainfall in the region across 20-40°N. Due to its increasing scientific and social importance, there have been several previous studies on identification of moisture sources for summer monsoon rainfall over East Asia mainly using Lagrangian or Eulerian atmospheric water vapor models. The major source regions for EASM previously proposed include the North Indian Ocean, South China Sea and North western Pacific. Based on high-precision and high-frequency 6-year measurement records of hydrofluorocarbons (HFCs), here we report a direct evidence of rapid intrusion of warm and moist tropical air mass from the Southern Hemisphere (SH) reaching within a couple of days up to 33°N into East Asia. We further suggest that the combination of direct chemical tracer record and a back-trajectory model with physical meteorological variables helps pave the way to identify moisture sources for monsoon rainfall. A case study for Gosan station (33.25°N, 126.19°E) indicates that the meridional transport of precipitable water from the SH accompanying the southerly/southwesterly flow contributes most significantly to its summer rainfall.

Terminal nerve gonadotrophin-releasing hormone (GnRH) neurones express multiple GnRH receptors in a teleost, the dwarf gourami (Colisa lalia).

Gonadotophin-releasing hormone (GnRH) peptide released from the terminal nerve (TN)-GnRH neurones of the dwarf gourami primarily modifies the electrical properties of various neurones, including the TN-GnRH neurones themselves. However, our knowledge on the expression of GnRH receptors (GnRHRs) in the TN-GnRH neurones is still limited. Here, we used the single-cell reverse transcriptase-polymerase chain reaction after whole-cell patch-clamp recording to study the distribution of various GnRHR types expressed in the individual TN-GnRH neurones. We found that TN-GnRH neurones express two of the three types of GnRHRs cloned in the dwarf gourami: GnRHR1-2 and -R2, but not -R1-1. Furthermore, in agreement with our previous findings, all TN-GnRH neurones contained mRNAs of salmon GnRH but not chicken GnRH-II.

Validation and reproducibility of food frequency questionnaire for Korean genome epidemiologic study.

OBJECTIVE: To evaluate validity and reliability of the food-frequency questionnaire (FFQ) developed for the Korean Genome Epidemiologic Study (KoGES). METHODS: FFQ was administered twice at 1-year interval (first FFQ (FFQ1) at the beginning and second FFQ (FFQ2) at the end of the study) and diet records (DRs) were collected for 3 days during each of the four seasons from December 2002 to May 2004 for those who attended the health examination center. At the end of the study period, we collected the 12-day DRs of 124 participants. The nutrient intakes from the DRs were compared with both FFQ1 and FFQ2. RESULTS: The intakes of energy and some nutrients estimated from FFQ1 and FFQ2 were different from those assessed by the DRs. Especially, the consumption of carbohydrates was higher in FFQ1 and FFQ2 than in the DRs. The de-attenuated, age, sex and energy intake adjusted correlation coefficients between the FFQ2 and the 12-day DRs in Korean population ranged between 0.23 (Vitamin A) and 0.64 (carbohydrate). The median for all nutrients was 0.39. The correlations were similar when we compared nutrient densities of both methods. Joint classification of calorie-adjusted nutrient intakes assessed by FFQ2 and 12-day DRs by quartile ranged from 25.8% (vitamin A) to 39.5% (carbohydrate, iron) for exact concordance. Except vitamin A, the proportion of subjects classified into distant quartile was less than 7% in all nutrients. The median of correlations between the two FFQs 1 year apart were 0.45 for all nutrient intakes and 0.39 for nutrient densities. CONCLUSIONS: We conclude that the FFQ we have developed appears to be an acceptable tool for assessing the nutrient intakes in this population. Further studies for calibration of the FFQ collected from multicenters participating in the KoGES are needed. SPONSORSHIP: This study was supported by the budget of the National Genome Research Institute, Korea National Institute of Health (2002-347-6111-221).

LSD1 demethylates HIF1α to inhibit hydroxylation and ubiquitin-mediated degradation in tumor angiogenesis.

Lysine-specific demethylase 1 (LSD1), which has been considered as a potential therapeutic target in human cancer, has been known to regulate many biological functions through its non-histone substrates. Although LSD1-induced hypoxia-inducible factor alpha (HIF1α) demethylation has recently been proposed, the effect of LSD1 on the relationship between HIF1α post-translational modifications (PTMs) and HIF1α-induced tumor angiogenesis remains to be elucidated. Here, we identify a new methylation site of the HIF1α protein antagonized by LSD1 and the interplay between HIF1α protein methylation and other PTMs in regulating tumor angiogenesis. LSD1 demethylates HIF1α at lysine (K) 391, which protects HIF1α against ubiquitin-mediated protein degradation. LSD1 also directly suppresses PHD2-induced HIF1α hydroxylation, which has a mutually dependent interplay with Set9-mediated HIF1α methylation. Moreover, the HIF1α acetylation that occurs in a HIF1α methylation-dependent manner is inhibited by the LSD1/NuRD complex. HIF1α stabilized by LSD1 cooperates with CBP and MTA1 to enhance vascular endothelial growth factor (VEGF)-induced tumor angiogenesis. Thus, LSD1 is a key regulator of HIF1α/VEGF-mediated tumor angiogenesis by antagonizing the crosstalk between PTMs involving HIF1α protein degradation.

The endoplasmic reticulum: one continuous or several separate Ca(2+) stores?

The Ca2+ store and sink in the endoplasmic reticulum (ER) is important for Ca2+ signal integration and for conveyance of information in spatial and temporal domains. Textbooks regard the ER as one continuous network, but biochemical and biophysical studies revealed apparently discrete ER Ca2+ stores. Recent direct studies of ER lumenal Ca2+ movements show that this organelle system is one continuous Ca2+ store, which can function as a Ca2+ tunnel. The concept of a fully connected ER network is entirely compatible with evidence indicating that the distribution of Ca2+ -release channels in the ER membrane is discontinuous with clustering in certain localities.

Identification and molecular characterization of three GnRH ligands and five GnRH receptors in the spotted green pufferfish.

Gonadotropin-releasing hormone (GnRH) is thought to have diverse physiological functions. Understanding regulatory mechanisms of GnRH functions requires detailed knowledge of gene expressions of both GnRH ligands and receptors in a single species. This report concerns identification and molecular characterization of GnRH ligands and receptors in the spotted green pufferfish Tetraodon nigroviridis. It was identified that the pufferfish possessed three types of GnRH ligands and five types of GnRH receptors. All types of ligands and receptors showed different expression patterns, and were widely expressed both inside and outside the brain. Gonads expressed all the ligand and receptor subtypes. Two of five receptor subtypes could not be detected in the pituitary gland of reproductively active individuals, suggesting the existence of novel GnRH systems independent of hypothalamic-pituitary-gonadal axis. Alternative splicing was also observed for some receptor subtypes. The present results indicate that diversified gene expressions combined with molecular diversity contribute to the functional diversity of GnRH.

Primary structure of a novel gonadotropin-releasing hormone in the brain of a teleost, Pejerrey.

The neuropeptide GnRH is the major regulator of reproduction in vertebrates acting as a first signal from the hypothalamus to pituitary gonadotropes. Three GnRH molecular variants were detected in the brain of a fish, pejerrey (Odontesthes bonariensis), using chromatographic and immunological methods. The present study shows that one form is identical to chicken GnRH-II (sequence analysis and mass spectrometry) and the second one is immunologically and chromatographically similar to salmon GnRH. The third form was proven to be a novel form of GnRH by isolating the peptide from the brain and determining its primary structure by chemical sequencing and mass spectrometry. The sequence of the novel pejerrey GnRH is pGlu-His-Trp-Ser-Phe-Gly-Leu-Ser-Pro-Gly-NH(2), which is different from the known forms of the vertebrate and protochordate GnRH family. The new form of GnRH is biologically active in releasing gonadotropin and GH from pituitary cells in an in vitro assay.

Nicotinic acetylcholine receptor-mediated release of [3H]norepinephrine from developing and adult rat hippocampus: direct and indirect mechanisms.

The primary role of nicotinic acetylcholine receptors in adult and developing brain is to modulate neurotransmission. Using in vitro neurotransmitter release, we have examined mechanisms underlying nicotine-induced [(3)H]norepinephrine release from developing and adult rat hippocampus. At birth, nicotine significantly stimulated hippocampal [(3)H]norepinephrine release with a monotonic increase in maximal drug effect over the first ten postnatal days. No developmental changes in agonist or antagonist potency were observed. Comparison of synaptosomal and slice preparations, as well as examination of the effects of tetrodotoxin, indicated that at least two nicotinic acetylcholine receptor populations regulated [(3)H]norepinephrine release from neonatal and adult hippocampus; one localized on noradrenergic terminals, the other on adjacent cells. To further characterize the indirect mechanism of nicotine action in the adult, we examined the effects of pharmacological blockade of various neurotransmitter systems that provide excitatory input to hippocampal noradrenergic terminals. Whereas glutamate and muscarinic receptor blockade was ineffective, the GABA-A receptor antagonists, bicuculline and picrotoxin, inhibited the indirect component of nicotine-mediated [(3)H]norepinephrine release. Furthermore, pentobarbital, an allosteric effector at GABA-A receptors, potentiated the effect of submaximal concentrations of nicotine. These findings are consistent with the hypothesis that nicotine-induced GABA release serves as an additional stimulus for [(3)H]norepinephrine secretion within rat hippocampus.