[Investigation and analysis of airborne allergenic pollen in 4 districts and 5 counties of Hohhot City].

Objective: To investigate the species, concentration and seasonal trends of main airborne allergenic pollen in 4 districts and 5 counties of Hohhot City. Methods: The Department of allergy, Beijing Shijitan Hospital Affiliated to Capital Medical University conducted a cross-sectional study about monitoring the airborne allergenic pollen from August 1, 2021 to July 31, 2022 by the gravitational method in 4 districts and 5 counties of Hohhot City, which include Yuquan District, Xincheng District, Huimin District, Saihan District, Tuoketuo County, Helingeer County, Tumotezuoqi County, Wuchuan County and Qingshuihe County. Daily pollens were counted and identified by optical microscopy, and the data were analyzed. Results: The airborne allergenic pollen was collected every month all year round in 4 districts and 5 counties of Hohhot city. Through the whole year of the total quantity of pollens ranged from 24 850 to 50 154 grains per 1 000 mm2 and two peaks of pollen concentration in air were observed,which happened in spring (from March to May) and in summer and autumn (from July to September). In spring, the main pollens were tree pollens, which principally distributed in Populus pollen (18.29%), Ulmus pollen (8.36%), Pinus pollen (6.20%), Cupressaceae pollen (5.23%), Betulaceae pollen (2.73%), Salix pollen (1.80%) and Quercus pollen (1.16%). In summer and autumn, the main pollens were weed pollens, which mainly included Artemisia pollen (42.73%), Chenopodiaceae pollen or Amaranthaceae pollen (7.46%), Poaceae pollen (2.26%), Humulus pollen or Cannabis pollen (0.60%). Conclusion: There were two peaks of main airborne allergenic pollen in 4 districts and 5 counties of Hohhot City. In the spring peak of pollen, the main airborne pollens were tree pollens. In the summer and autumn peak of pollen, the main airborne pollens were weed pollens. The Artemisia pollen was the most major airborne pollen in this area.

A study on correlations between precipitation ETCCDI and airborne pollen/fungal spore parameters in the NE Iberian Peninsula.

Precipitation is one of the meteorological variables usually involved in the aerobiological studies, which presents a complex relationship with atmospheric levels of pollen and fungal spores and the temporal characteristics of their seasons. This complexity is due in a large part to rainfall's twofold impact of having, prior to pollination, a positive influence on subsequent pollen production and of contributing, during pollination, to pollen removal from the air through a wash-out effect. To better explore this impact, we place particular emphasis on extreme rainfall by calculating the correlation between airborne pollen and fungal spore parameters and the precipitation indices that the Expert Team on Climate Change Detection and Indices (ETCCDI) proposed for characterising climate extremes. Parameters for twenty-seven pollen and fungal spore taxa measured in six aerobiological stations in the NE Iberian Peninsula have been considered. We have distinguished between annual and winter ETCCDI in order to compare the correlations between extreme rainfall and airborne pollen concentrations and to avoid the wash-out effect as far as possible. Results show a positive influence from an increase in moderately extreme winter rainfall, specifically on subsequent pollen/fungal spore production: the percentage of all possible significant correlations is higher for winter than for annual rainfall. Furthermore, while annual rainfall in this region has nearly the same number of positive as negative correlations, the positive correlations for winter rainfall are more than twice that of the negative ones. The seasonal consideration on rainfall ETCCDI made with the aim to avoid the confounding overlapping of different rainfall impacts has led to more sharpened observations of its positive and negative effects on airborne pollen and fungal spore concentrations.

Antibacterial activity and mechanism of chloroform fraction from aqueous extract of mugwort leaves (Artemisia argyi L.) against Staphylococcus aureus.

In this work, the antibacterial activity and mechanism of chloroform fraction obtained from aqueous extract of mugwort leaves against Staphylococcus aureus were investigated. The extract showed obvious antibacterial activity against S. aureus which the minimum inhibitory concentration and minimum bactericidal concentration were determined to be 3·0 and 6·0 mg ml-1 respectively. The mechanism study suggested that the extract could destroy the integrity of the S. aureus cell walls and increase the permeability of cell membrane in a certain concentration, but it could not kill S. aureus in a short time. Instead, the extract could make bacteria in a state of apoptosis for a long time, interfere with the normal physiological metabolism of bacteria, and eventually make bacteria die, which was confirm by scanning electronic microscope.

Photosynthetic performance and growth responses of Liriope muscari (Decne.) L.H. Bailey (Asparagaceae) planted within poplar forests having different canopy densities.

BACKGROUND: Liriope muscari (Decne.) L.H. Bailey is a valuable horticultural and medicinal plant that grows under a range of light intensities, from high to low, in the understories of shrubs. To understand how this species adapts to these various environments, we selected two groups of lilyturf growing under poplar trees at two different spacings. Each group was divided into three types, open field, forest edge and shaded forest with high, medium and low irradiance levels, respectively, and then we examined their photosynthetic characteristics, physiology and biomasses. RESULTS: Light saturation point, light compensation point and in situ net photosynthetic rate (PN) were highest in lilyturf growing under high light. In contrast, lilyturf growing under low light had a higher apparent quantum yield and Chl a and b contents, indicating that they adapted to low light. Although the leaves of lilyturf growing under low light were small, their root tubers were heavier. CONCLUSIONS: The research demonstrates the eco-physiological basis of lilyturf's shade adaptation mechanism as indicated by photosynthetic activity, chlorophyll fluorescence, Chl a, Chl b and Car contents when grown under different irradiances. We believe that lilyturf is a shade-tolerant plant suitable for planting in undergrowth, but attention should be paid to the canopy density of the forest when interplanting. The findings presented here advance our understanding of the photosynthetic characteristics of understory plants and may assist in the optimization of irradiances in the future.

[Identification of Two GLOBOSA-like MADS-box Genes in Tea Plant (Camellia sinensis [L.] O. Kuntze)].

Tea plant (Camellia sinensis [L.] O. Kuntze) is a woody crop of high economic importance worldwide; however, information on the molecular mechanisms underlying the regulation of flower development in this species is limited. In the present study, two GLOBOSA (GLO) -like MADS-box genes, CsGLO1 and CsGLO2, were isolated from C. sinensis 'Ziyangzhong' and were characterized to elucidate their roles in flower development. We found that CsGLOl and CsGLO2 are nuclear-localized transcription factors without transactivation ability but with a robust interaction. They have similar patterns of expression, both mainly restricted to petals and stamens. Moreover, ectopic expression of either CsGLO1 or CsGLO2 in Arabidopsis thaliana resulted in a partial conversion of sepals to petals, suggesting full GLOBOSA functional activity. Our results indicate that CsGLO1 and CsGLO2 paralogs might redundantly contribute to petal and stamen, providing the first insight into their role in tea plant flower development.

[Observation of the therapeutic and characteristic effects of terlipressin on refractory cirrhotic ascites].

Objective: To observe the therapeutic effect of terlipressin on refractory ascites (RA) in cirrhosis, and its role and impact on acute kidney injury (AKI). Methods: A non-randomized controlled clinical trial data of 111 hospitalized cases of liver cirrhosis accompanied with RA was collected from Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Zhongshan Hospital of Hubei Province, The First Affiliated Hospital of Zhengzhou University, The First Affiliated Hospital of Medical School of Zhejiang University, and People's Hospital of Pudong New Area of Shanghai between March 2015 and March 2017. 26 cases of conventional treatment group (control group) were divided into two subgroups: RA without AKI (RA-NAKI) and RA with AKI (RA-AKI), and each subgroup consisted 13 cases. Patients with bacterial infection were treated with diuretics, albumin supplementation and antibiotics. 85 cases were presented in terlipressin combined treatment group, of which 27 cases were of RA-NAKI and 58 cases were of RA-AKI. Control group was injected terlipressin 1mg of intravenous drip or static push (once q6 h ~ 12 h) for more than 5 days. The treatment duration lasted for 2 weeks with 4 weeks of follow-up. Body weight, 24-hour urine volume, abdominal circumference, mean arterial pressure (MAP), liver and kidney function, anterior hepatic ascites, deepest point of ascites, and ultrasonographic detection of ascites in supine position before treatment, one and two weeks after treatment and 4 weeks after follow-up were compared. Count data were tested by χ (2). Samples of four groups at baseline were compared. One-way analysis of variance was used for normal distribution data and Kruskal-Wallis H test for non-normal distribution data. Repeated measures analysis of variance was used to compare the difference in efficacy between different time points before and after treatment in the group. The LSD method of one-way ANOVA was used to compare the two groups. A t-test of independent samples was used to compare the efficacy of different time series between the two groups. Mann-Whitney rank- sum test was used to compare the data of non-normal distribution between the two groups. Results: (1) Baseline data were compared among 4 subgroups of terlipressin RA-NAKI and control RA-AKI. Control group age was higher than that of terlipressin group, and the serum creatinine (SCr) of the RA-AKI group was higher than RA-NAKI group, and there was no significant difference in the rest of the baseline data and the combined medication (P > 0.05). (2) An intra-group comparison between control and trelipressin before and after treatment showed that all patients had lower body mass, abdominal circumference and deepest ascites, and higher serum albumin (P < 0.05). 24-hour urine volume and MAP was significantly increased in the terlipressin group, while the pre-ascites, SCr and child Turcotte Pugh (CTP) scores were decreased. Body weight, abdominal circumference, pre-ascites, and deepest ascites of the terlipressin group were decreased, while MAP was increased during the treatment and follow-up periods. The differences were statistically significant when compared with the control group at the same time (P < 0.05). There was a statistically significant difference in the increase of 24-h urine volume in the terlipressin group compared with the control group (P < 0.05). The decrease in SCr and CTP in the terlipressin group after 2 weeks of treatment and 4 weeks of follow-up was statistically significant compared with the control group (P < 0.05). (3) Among the two subgroups of RA-AKI and RA-NAKI in the terlipressin group, the baseline SCr value of the former was higher than that of the latter. After treatment, the body weight, abdominal circumference, pre-ascites, deepest ascites and CTP scores were decreased. In the RA-AKI group, 24-hour urine volume, MAP, SCr and serum albumin concentration were significantly increased. The difference between the two subgroups before and after treatment was compared, and the body weight of RA-AKI group at 1, 2 weeks of treatment and 4 weeks of follow-up was significantly lower than RA-NAKI group, which were (- 2.3 ± 0.2 vs. - 1.5 ± 0.2) kg, (- 4.1 ± 0.2 vs. - 2.6 ± 0.2) kg, (- 4.2 ± 0.3 vs. - 2.4 ± 0.3) kg, respectively. RA-NAKI group urine volume was significantly increased at 2 weeks of treatment and 4 weeks of follow-up, which was (468 ± 42 vs. 110 ± 131) ml, (272 ± 34 ml vs. 11 ± 112) ml, respectively. SCr reduction (18.3 ± 4.7 vs. 0.9 ± 2.4) µmol/l at 4 weeks of follow-up was apparent in RA-NAKI group, and the difference was statistically significant (P < 0.05). Conclusion: Addition of terlipressin to conventional treatment may significantly increase MAP, 24-h urine volume, improve renal function and promote ascites resolution in patients with refractory cirrhotic ascites. Moreover, its combination effect is more obvious in AKI patients, and adverse reactions are mild.

N(6)-(3-methoxyl-4-hydroxybenzyl) adenine riboside induces sedative and hypnotic effects via GAD enzyme activation in mice.

BACKGROUND AND PURPOSE: N(6)-(3-methoxyl-4-hydroxybenzyl) adenine riboside (B2) is an analog of N(6)-(4-hydroxybenzyl) adenine riboside (NHBA), which was originally isolated from Gastrodia elata Blume. Our laboratory has previously demonstrated that B2 can produce strong sedative and hypnotic effects, but the mechanism remains to be determined. There is evidence that gamma-aminobutyric acid (GABA) acts as an inhibitory neurotransmitter in the brain, plays a major role in sleep regulation, and participates in the sedative and hypnotic effects of B2. Therefore, we studied the interactions between B2 and several GABAergic neurochemical parameters based on the sedative and hypnotic effects of B2. EXPERIMENTAL APPROACH: The GABA and glutamic acid (Glu) in the mouse brain were derivatized with o-phthalaldehyde (OPA) and measured by high performance liquid chromatography-electrochemical detection (HPLC-ECD). The GAD and GABA-T enzyme activities were determined by measuring GABA and NADH production, respectively. The sleep structure analyses were performed by EEG studies in mice. KEY RESULTS: B2 increased the GABA levels and GAD enzyme activity in the mouse hypothalamus and cortex. The EEG results confirmed that B2 significantly shortened the sleep latency and increased the amount of NREM sleep. The GAD enzyme inhibitor semicarbazide (SCZ) blocked the sedative and hypnotic effects of B2. CONCLUSIONS AND IMPLICATIONS: These findings suggest that the GAD enzyme plays a significant role in the sedative and hypnotic effects of B2. Therefore B2 may be a promising candidate for further clinical studies and the appropriate use of GAD agonist may be a promising approach for sleep disorders.

Clinical observation of Danhong Injection (herbal TCM product from Radix Salviae miltiorrhizae and Flos Carthami tinctorii) in the treatment of traumatic intracranial hematoma.

Danhong Injection (DHI), a Chinese Materia Medica standardized product extracted from Radix Salviae Miltiorrhizae and Flos Carthami tinctorii, has the actions of promoting blood circulation and resolving stasis to promote regeneration. The clinical therapeutic effects of DHI on traumatic intracranial hematoma (TICH) were observed. Eighty patients with TICH were randomly assigned to trial group and a control group (40 patients per group), and all were administered with routine medication. Additionally, DIH was administered intravenously to patients in the trial group. Pre and post-treatment GCS was observed in the two groups, along with GOS after therapy. The intracranial hematoma absorption, hemorheological changes, and changes in coagulation indexes pre- and post-treatment were evaluated. The results indicated that GCS and GOS after therapy for the trial group were superior to those for the control group (p<0.05). There was a significant post-treatment difference in the intracranial hematoma absorption between the two groups (p<0.01). Each hemorheological index in the trial group improved significantly as compared with that of the control group (p<0.05 or p<0.01). The plasma levels of fibrinogen and D-dimer in the trial group were significantly decreased after therapy (p<0.01). These results suggest that DHI is conducive to the recovery of patients with TICH.

Effect of adding a Chinese herbal preparation to acupuncture for seasonal allergic rhinitis: randomised double-blind controlled trial.

OBJECTIVE: To assess whether the addition of a Chinese herbal medicine formula to acupuncture affects the severity of symptoms and quality-of-life scores among patients with seasonal allergic rhinitis. DESIGN: Randomised double-blind placebo-controlled trial. SETTING: University teaching and research clinic, Australia. PARTICIPANTS: Sixty-five patients with seasonal allergic rhinitis, who were recruited through public media. INTERVENTION: Between July and December 1999, patients received acupuncture twice a week for 8 weeks plus either a Chinese herbal drug formula (n=33) or placebo (n=32) at a dosage of four capsules, three times daily. MAIN OUTCOME MEASURES: The severity of nasal and non-nasal symptoms on a five-point scale, as assessed by both patients and an ear, nose, and throat specialist, and quality-of-life scores as measured by the Rhinoconjunctivitis and Rhinitis Quality of Life Questionnaire. RESULTS: Sixty-one patients completed the study (31 in the intervention group and 30 in the control group). After 8 weeks, no significant difference was found between the two groups in the severity of nasal and non-nasal symptoms and in the Rhinoconjunctivitis and Rhinitis Quality of Life Questionnaire scores. Intention-to-treat analysis of categorical variables showed moderate-to-marked improvement rates of 72.7% and 81.2% for intervention and control groups, respectively. Six patients reported mild adverse events-three from each of the study groups. CONCLUSION: The Chinese herbal formulation under investigation did not provide additional symptomatic relief or improvement in quality-of-life scores among patients with seasonal allergic rhinitis who were receiving acupuncture.

Evidence for novel caffeine and Ca2+ binding sites on the lobster skeletal ryanodine receptor.

1. The effects of Ca2+, ATP and caffeine on the gating of lobster skeletal muscle ryanodine receptors (RyR) was investigated after reconstitution of the channels into planar phospholipid bilayers and by using [3H]-ryanodine binding studies. 2. The single channel studies reveal that the EC50 (60 microM) for activation of the lobster skeletal RyR by Ca2+ as the sole ligand is higher than for any other isoform of RyR studied. 3. Inactivation of the channel by Ca2+ (EC50 = 1 mM) occurs at concentrations slightly higher than those required to inactivate mammalian skeletal RyR (RyR1) but lower than those required to inactivate mammalian cardiac RyR (RyR2). 4. Lifetime analysis demonstrates that cytosolic Ca2+, as the sole activating ligand, cannot fully open the lobster skeletal RyR (maximum Po approximately 0.2). The mechanism for the increase in open probability (Po) is an increase in both the frequency and the duration of the open events. 5. ATP is a very effective activator of the lobster RyR and can almost fully open the channel in the presence of activating cytosolic [Ca2+]. In the presence of 700 microM Ca2+, 1 mM ATP increased Po to approximately 0.8. 6. Caffeine, often used as a tool to identify the presence of RyR channels, is relatively ineffective and cannot increase Po above the level that can be attained with Ca2+ alone. 7. The results reveal that caffeine increases Po by a different mechanism to that of cytosolic Ca2+ demonstrating that the mechanism for channel activation by caffeine is not 'sensitization' to cytosolic Ca2+. 8. By studying the mechanisms involved in the activation of the lobster RyR we have demonstrated that the channel responds in a unique manner to Ca2+ and to caffeine. The results strongly indicate that these ligand binding sites on the channel are different to those on mammalian isoforms of RyR.

Regulation of apolipoprotein A-I gene expression in Hep G2 cells depleted of Cu by cupruretic tetramine.

Studies were designed to examine the regulation of apolipoprotein (apo) A-I gene expression in Cu-depleted Hep G2 cells. The cupruretic chelator N,N'-bis(2-aminoethyl)-1,3-propanediamine 4 HCl (2,3,2-tetramine or TETA) was used to maintain a 77% reduction in cellular Cu in Hep G2 cells. After two passages of TETA treatment, the relative abundance of apoA-I mRNA was elevated 52%. In TETA-treated cells, the rate of apoA-I mRNA decay measured by an actinomycin D chase study was accelerated 108%, and the synthesis of apoA-I mRNA determined by a nuclear runoff assay was enhanced 2.5-fold in TETA-treated cells. All of those changes could be reverted toward the control values with Cu supplementation for only 2 days. In transient transfection assays, a 26.7% increase in chloramphenicol O-acetyltransferase (CAT) activity for the reporter construct -256AI-CAT was observed in the treated cells. However, the ability of apoA-I regulatory protein 1 (ARP-1) to repress the CAT activity was not affected by the depressed Cu status. In addition, gel retardation experiments demonstrated that Cu depletion enhanced the binding of hepatocyte nuclear factor 4 (HNF-4) and other undefined nuclear factors to oligonucleotides containing site A, one of three regulatory sites of the apoA-I gene promoter. Moreover, the relative abundance of HNF-4 mRNA was increased 58% in the Cu-depleted cells. Thus the observed increase in apoA-I gene transcription may be mediated mostly by an elevated level of the regulatory factor, HNF-4. In summary, the present findings established the mechanism by which a depressed cellular Cu status can enhance apoA-I mRNA production and subsequently increase apoA-I synthesis.

[Study on sijunzi decoction in rectifying digestive disorder in mice].

OBJECTIVE: To observe the Sijunzi Decoction in rectifying the digestive disorder. METHODS: Sijunzi decoction (SJZD) was chosen to treat digestive dysfunction in mice. The model was induced by Xiaochengqi decoction and semi-starvation. The effects on the absorptive function of the small intestine, body weight, autonomous activity levels, oxidative phosphorylation of hepatic mitochondrion, respiratory control rate (RCR) and cells energy charge were observed in vivo. RESULTS: The group given Xiaochengqi decoction had lower absorption, decreased body weight, and lower autonomous activity levels, and their hepatic mitochondrion RCR and cell energy charge were also lower than those of the control group. The figures for the group given SJZD all showed improvement, especially the group given the larger dose of SJZD. CONCLUSION: SJZD could correct Deficiency of the Spleen and Stomach which to some extent is caused by digestive dysfunction. So it is considered that the Spleen's function of transportation and transformation includes two meanings: external transportation and transformation--the digestive and absorptive function of the small intestine, and internal transportation and transformation--the liver's conversion of nutrients and generate energy (ATP).

Electrophysiological and morphological properties of pyramidal and nonpyramidal neurons in the cat motor cortex in vitro.

Electrophysiological and morphological properties of the neurons in cat motor cortex were investigated using intracellular recording and staining techniques in a brain slice preparation. In response to intracellular injection of depolarizing current pulses, four distinct types of firing patterns were observed among cat neocortical neurons. Regular-spiking neurons were characterized by their repetitive firing from which conspicuous frequency adaptation was observed. Doublet-or-burst firing cells were marked with their tendency to fire 2-5 clustered spikes at the onset of depolarizing pulse. In doublet-or-burst firing neurons, but not in regular-spiking neurons, a low-threshold calcium current was revealed by single-electrode voltage clamp. Both regular-spiking and doublet-or-burst firing neurons had relatively wide action potentials. Fast-spiking neurons could fire extremely narrow action potentials at a very high frequency. Their frequency-to-intensity slope of steady-state firing was significantly higher than that of the other neurons. In contrast, narrow-spiking neurons had the smallest frequency-to-intensity slope for steady-state firing, although their action potentials were as narrow as those of the fast-spiking neurons. Both regular-spiking and doublet-or-burst firing neurons were identified as pyramidal neurons, and were found in all layers below layer I. Their apical dendrites were densely coated with dendritic spines. Narrow-spiking neurons were only recorded in layer V. They were large pyramidal cells with scare spines on their apical dendrites. Fast-spiking neurons were all nonpyramidal interneurons. Seven out of eight labelled fast-spiking cells had beaded dendrites without spines. Their axons had a large number of varicosities, and arborized extensively to form a dense plexus of terminals in the vicinity of their soma. The remaining neuron was found to be a spiny nonpyramidal neuron in layer V. These results demonstrate that, in addition to the three types of firing patterns previously identified in rodent neocortex, a group of neurons in the cat motor cortex express another type of firing behaviour which is characterized by extremely narrow action potential and very small frequency-to-intensity slope. Correlation with the morphological data shows that these neurons are large layer V pyramidal cells rather than nonpyramidal interneurons.

Different mechanisms underlying the repolarization of narrow and wide action potentials in pyramidal cells and interneurons of cat motor cortex.

Two different types of action potentials were observed among the pyramidal cells and interneurons in cat motor cortex: the narrow action potentials and the wide action potentials. These two types of action potentials had similar rising phases (528.8 +/- 77.0 vs 553.1 +/- 71.8 mV/ms for the maximal rising rate), but differed in spike duration (0.44 +/- 0.09 vs 1.40 +/- 0.39 ms) and amplitude (57.31 +/- 8.22 vs 72.52 +/- 8.31 mV), implying that the ionic currents contributing to repolarization of these action potentials are different. Here we address this issue by pharmacological manipulation and using voltage-clamp technique in slices of cat motor cortex. Raising extracellular K+ concentration (from 3 mM to 10 mM), applying a low dose of 4-aminopyridine (2-200 microM) or administering a low concentration of tetraethylammonium (0.2-1.0 mM) each not only broadened the narrow action potentials, but also increased their amplitudes. In contrast, high K+ medium or low dose of tetraethylammonium only broadened the wide action potentials, leaving their amplitudes unaffected, and 4-aminopyridine had only a slight broadening effect on the wide spikes. These results implied that K+ currents were involved in the repolarization of both types of action potentials, and that the K+ currents in the narrow action potentials seemed to activate much earlier than those in the wide spikes. This early activated K+ current may counteract the rapid sodium current, yielding the extremely brief duration and small amplitude of the narrow spikes. The sensitivity of the narrow spikes to 4-aminopyridine may not be mainly attributed to blockade of the classical A current (IA), because depolarizing the membrane potential to inactivate IA did not reproduce the effects of 4-aminopyridine. Blockade of Ca2+ influx slowed the last two-thirds repolarization of the wide action potentials. On the contrary, the narrow action potentials were not affected by Ca(2+)-current blockers, but if they were first broadened by 4-aminopyridine or tetraethylammonium, subsequent application of Ca(2+)-free medium caused further broadening, suggesting that the narrow action potentials were too brief to activate the Ca(2+)-activated potassium currents for their repolarization. Therefore, the effects of low concentrations of tetraethylammonium on the narrow spikes appeared to be mainly due to blockade of an outward current that was different from the tetraethylammonium-sensitive Ca(2+)-activated potassium current (IC). In the neurons with the narrow spikes, voltage-clamp experiments revealed two voltage-gated outward currents that were sensitive to tetraethylammonium and 4-aminopyridine, respectively. Both currents were activated rapidly following the onset of depolarizing steps. Interestingly, the tetraethylammonium-sensitive current was a transient outward current that inactivated rapidly (tau < or = 5 ms), while the 4-aminopyridine-sensitive current was relatively persistent during maintained depolarization. The 4-aminopyridine-sensitive current did not show obvious inactivation even at membrane potential of -40 mV, which completely inactivated the transient tetraethylammonium-sensitive, current. The results indicate that different potassium currents are involved in the repolarization of the narrow and wide action potentials in cat motor cortex. A novel tetraethylammonium-sensitive transient outward current and a 4-aminopyridine-sensitive outward current are responsible for the short duration and small amplitude of the narrow action potentials in the interneurons and some of the layer V pyramidal cells. These two currents are voltage-gated and Ca(2+)-independent. For the wide action potentials that characterize most pyramidal neurons, a Ca(2+)-independent tetraethylammonium-sensitive outward current and a Ca(2+)-activated potassium current are the main contributors to their repolarization.

GABAA receptor-mediated feedback inhibition in pyramidal neurons of cat motor cortex.

Feedback or recurrent inhibition is generally proposed as a basic component of circuit organization in the brain. However, there is little direct evidence for its existence in the cortex, nor for the nature of the neurotransmitters and receptors involved. Here we address this issue by analyzing the potentials following a single action potential in cat neocortical pyramidal neurons. Using 3 M KCl-filled electrodes, we observed a distinct depolarizing potential that was superimposed on the spike after-potentials in seven out of 81 recorded and the resemblance between its falling phase and the passive decay of membrane potential suggested that the depolarizing potential originated from the cell body or proximal dendrites. This potential was blocked by bicuculline methiodide (10 microM), but not by phaclofen (0.2 mM), suggesting that it was a reversed recurrent IPSP mediated by GABAA receptors.