Capecitabine and vinorelbine in elderly patients (≥65 years) with metastatic breast cancer: a phase I trial (SAKK 25/99)

BACKGROUND

Few chemotherapy regimens are suitable for the treatment of elderly patients with advanced breast cancer. With the aim of finding a regimen with a low burden of subjective non-overlapping toxic effects, vinorelbine and capecitabine were chosen to be investigated in a phase I dose-finding study.

PATIENTS AND METHODS

Thirty-six patients with advanced breast cancer were stratified for the presence of bone and non-bone involvement and treated at four dose levels from capecitabine 800 mg/m2 orally days 1-14 and vinorelbine 20 mg/m2 intravenously days 1 and 8, to capecitabine 1250 mg/m2 orally days 1-14 and vinorelbine 25 mg/m2 intravenously days 1 and 8, for a maximum of six cycles. None of the patients had received prior chemotherapy for metastatic/advanced disease. Fifty-three per cent of patients with bone metastases and 67% of patients without bone metastases had visceral disease. The median age was 70 years for the 15 with bone involvement patients and 73 years for the 21 without bone involvement patients.

RESULTS

Twenty-eight patients were fully evaluable for hematological dose-limiting toxicity (DLT), and all patients for other DLTs and for antitumor activity. One DLT with grade 3 venous thrombosis at dose level 2 and two dose-limiting neutropenia events at level 3 occurred in patients without bone involvement. Two dose-limiting neutropenia events were observed at dose level 2 for patients with bone involvement. Thus, the recommended dose was defined at level 1 (capecitabine 1000 mg/m2 days 1-14 and vinorelbine 20 mg/m2 days 1 and 8) for patients with bone involvement. For patients without bone involvement, the recommended dose was at level 2 (capecitabine 1250 mg/m2 days 1-14 and vinorelbine 20 mg/m2 days 1 and 8). For patients without bone involvement the overall response rate was 48% and the time to progression (TTP) was 4.5 months [95% confidence interval (CI) 3.3-6.9]. For patients with bone involvement the overall response rate was 53% and TTP was 5.3 months (95% CI 2.7-7.8).

CONCLUSIONS

This regimen of capecitabine and vinorelbine is well tolerated and effective in elderly patients with metastatic breast cancer. Toxicity was mainly hematological and was observed at a lower dose in patients with bone involvement. A phase II study with the two different dose levels for elderly patients with and without bone involvement is currently being conducted.

Control of the temporal fidelity of synaptic transmission by a presynaptic high voltage-activated transient K+ current

The type of K(+) channels controlling the waveform of the presynaptic spike and synaptic transmission were examined in the lamprey spinal cord. Reticulospinal neuron somata displayed a transient K(+) current with a high voltage-activation and inactivation. This current was selectively blocked by catechol at 100 microM. Reticulospinal axons also displayed a high voltage-activated fast K(+) current sensitive to catechol. The function of this presynaptic high voltage-activated fast K(+) current in controlling synaptic transmission was investigated by using paired intracellular recordings from reticulospinal axons and their targets. Blockade of this current by catechol (100 microM) prolonged the presynaptic spike elicited by a single stimulus leading to a potentiation of the postsynaptic EPSP. Calcium imaging of reticulospinal axons showed an increase in presynaptic calcium transients after blockade of the presynaptic K(+) current by catechol. During high frequency firing, catechol revealed an activity-dependent decrease in the spike duration, which resulted in a depression of synaptic transmission. These results suggest that the presynaptic high voltage-activated transient K(+) current acts to optimize the temporal fidelity of synaptic transmission by minimizing activity-dependent changes in the presynaptic spike waveform and calcium dynamics.

The "cost" of operative training for surgical residents

HYPOTHESIS

There is an increase in the amount of time required to perform an operation when the procedure involves training a surgical resident. This increased time does not translate into a financial burden for the hospital.

DESIGN

Retrospective review of prospectively collected data. During the study period, surgeons and residents were blinded to the study's intent. We compared the operative times of academic surgeons performing 4 common surgical procedures before and after the introduction of a postgraduate year 3 resident into a community teaching hospital. Between January 1, 2001, and June 30, 2002, 4 academic surgeons performed operations without a resident in a community hospital that was recently integrated into a tertiary medical center system. During that period, surgeons operated alone (hernia surgery) or assisted one another (laparoscopic cholecystectomy, colectomy, and carotid endarterectomy). From July 1, 2002, through March 31, 2003, these same 4 surgeons were assisted by a postgraduate year 3 resident on similar procedures.

SETTING

Community hospital recently integrated into a tertiary medical center system.

PARTICIPANTS

Four experienced academic surgeons operating in the community setting and patients undergoing 1 of 4 surgical procedures (inguinal hernia repair, laparoscopic cholecystectomy, partial colectomy, or carotid endarterectomy) from January 1, 2001, through March 31, 2003.

INTERVENTION

The introduction of a postgraduate year 3 surgical resident rotation into a community hospital in which the same academic surgeons had been performing operations without a resident for 18 months.

MAIN OUTCOME MEASURES

Mean operating time with and without a postgraduate year 3 resident participating in 4 common surgical procedures. Result For the 4 procedures studied, there was a significant increase in the operative time required to complete such procedures.

CONCLUSIONS

There is an increased time cost associated with the operative training of surgical residents. This "cost" primarily impacts the attending surgeon.

Glufosfamide administered using a 1-hour infusion given as first-line treatment for advanced pancreatic cancer. A phase II trial of the EORTC-new drug development group

The activity of glufosfamide (beta-D-glucopyranosyl-N,N'-di-(2-chloroethyl)-phosphoric acid diamide) against pancreatic cancer was investigated in a multicentre, phase II clinical study. Chemotherapy-nai;ve patients with advanced or metastatic disease were treated with glufosfamide (5 g/m(2)) using a 1-h intravenous (i.v.) infusion every 3 weeks. Patients were randomised between active-hydration and normal fluids to evaluate the nephroprotective effect of forced diuresis. Patients experiencing >0.4 mg/dl (>35 micromol/l) increase in serum creatinine compared with their baseline value were taken off treatment for safety reasons. The evaluation of response was according to the Response evaluation criteria in solid tumours (RECIST). Blood sampling was performed for pharmacokinetic analyses. 35 patients from 13 institutions were registered over a 13-month period. A total of 114 treatment cycles (median 3, range 1-8) were administered to 34 patients; 18 patients were allocated to the hydration arm. Overall haematological toxicity was mild. Metabolic acidosis occurred in 2 patients treated in the active-hydration arm, grade 3 hypokalaemia was recorded in 5 patients and grade 3 hypophosphataemia in 4 patients. One patient had a grade 4 increase in serum creatinine level, concomitantly to disease progression. Active-hydration did not show a nephroprotective effect and the plasma pharmacokinetics (Pk) of glufosfamide was not significantly influenced by hydration. Two confirmed partial remissions (PR) were reported (response rate 5.9%, 95% Confidence Interval (CI) 0.7-19.7%) and 11 cases obtained disease stabilisation (32.4%). An extra mural review panel confirmed all of the responses. Median overall survival was 5.3 months (95% CI 3.9-7.1) and time to progression (TTP) was 1.4 months (95% CI 1.3-2.7). In conclusion, glufosfamide administered using a 1-h infusion every 3 weeks has a modest activity in advanced pancreatic adenocarcinoma. Haematological toxicity is particularly mild, but regular monitoring of renal function is recommended.

Phase I and pharmacokinetic studies of PNU-159548, a novel alkycycline, administered intravenously to patients with advanced solid tumours

PNU-159548 (4-demethoxy-3'-deamino-3'-aziridinyl-4'-methylsulphonyl-daunorubicin) is the lead compound of a novel class of cytotoxic agents (alkycyclines) with a unique mechanism of action combining DNA intercalation with alkylation of guanines in the DNA major groove. The objectives of two phase I studies were to assess the dose-limiting toxicities (DLTs), to determine the maximum tolerated dose (MTD) and to study the pharmacokinetics (PKs) of PNU-159548 and its active metabolite PNU-169884 when administered intravenously (i.v.) over 10 or 60 min to patients with advanced solid tumours. Patients were treated with escalating doses of PNU-159548, courses repeated every 21 days at doses ranging from 1.0 to 16 mg/m(2). For pharmacokinetic analysis, plasma sampling was performed during the first course and assayed using a validated high-performance liquid chromatographic assay with mass spectrometric detection. 69 patients received a total of 161 courses. The MTD was reached at 14 and 16 mg/m(2) in heavily (HP) and minimally pretreated/non-pretreated (MP) patients, respectively, with thrombocytopenia as the DLT. A hypersensitivity reaction was observed in 8 patients across all dose levels, characterised by fever with chills, erythema, facial oedema and dyspnoea. The PKs of PNU-159548 and PNU-169884 were linear over the dose range studied. A significant correlation was observed between the percentage decrease in platelet count and the AUC of PNU-159548. In these studies, the DLT of PNU-159548 was thrombocytopenia. The recommended dose for phase II studies of PNU-159548 is 12 and 14 mg/m(2) administered i.v. over 10 min, once every 21 days, in HP and MP patients, respectively.

Prospective two year follow up study comparing novel and conventional imaging procedures in patients with arthritic finger joints

OBJECTIVE

To carry out a prospective two year follow up study comparing conventional radiography, three-phase bone scintigraphy, ultrasonography (US), and three dimensional (3D) magnetic resonance imaging (MRI) with precontrast and dynamic postcontrast examination in detecting early arthritis. The aim of the follow up study was to monitor the course of erosions during treatment with disease modifying antirheumatic drugs by different modalities and to determine whether the radiographically occult changes like erosive bone lesions of the finger joints detected by MRI and US in the initial study would show up on conventional radiographs two years later. Additionally, to study the course of soft tissue lesions depicted in the initial study in comparison with the clinical findings.

METHODS

The metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints (14 joints) of the clinically more severely affected hand (soft tissue swelling and joint tenderness) as determined in the initial study of 49 patients with various forms of arthritis were examined twice. The patients had initially been divided into two groups. The follow up group I included 28 subjects (392 joints) without radiographic signs of destructive arthritis (Larsen grades 0-1) of the investigated hand and wrist, and group II (control group) included 21 patients (294 joints) with radiographs showing erosions (Larsen grade 2) of the investigated hand or wrist, or both, at the initial examination.

RESULTS

(1) Radiography at the two year follow up detected only two erosions (two patients) in group I and 10 (nine patients) additional erosions in group II. Initial MRI had already detected both erosions in group I and seven (seven patients) of the 10 erosions in group II. Initial US had depicted one erosion in group I and four of the 10 erosions in group II. (2) In contrast with conventional radiography, 3D MRI and US demonstrated an increase in erosions in comparison with the initial investigation. (3) The abnormal findings detected by scintigraphy were decreased at the two year follow up. (4) Both groups showed a marked clinical improvement of synovitis and tenosynovitis, as also shown by MRI and US. (5) There was a striking discrepancy between the decrease in the soft tissue lesions as demonstrated by clinical findings, MRI, and US, and the significant increase in erosive bone lesions, which were primarily evident at MRI and US.

CONCLUSIONS

Despite clinical improvement and a regression of inflammatory soft tissue lesions, erosive bone lesions were increased at the two year follow up, which were more pronounced with 3D MRI and less pronounced with US. The results of our study suggest that owing to the inadequate depiction of erosions and soft tissue lesions, conventional radiography alone has limitations in the intermediate term follow up of treatment. US has a high sensitivity for depicting inflammatory soft tissue lesions, but dynamic 3D MRI is more sensitive in differentiating minute erosions.

Infection control in the intensive care unit. The role of the ventilator circuit

Patients are more likely to develop VAP from secretions aspirated past the cuff of the endotracheal tube than by what is breathed through the endotracheal tube. It may be more accurate to use the term "airway-associated pneumonia" rather than "ventilator-associated pneumonia" Several studies have now reported no change in VAP rates when circuits are only changed on an at-needed basis. There is also accumulating evidence that passive humidifiers and closed suction catheters do not need to be changed on a daily basis.

Noninvasive pressure support ventilation

In appropriately selected patients, NPPV decreases intubation rate, improves survival, and is cost-effective. Pressure support ventilation is commonly used successfully for NPPV. An issue with the use of pressure support is the ability of the ventilator to detect the end of inhalation in the presence of leaks or in patients with severe airflow obstruction. A concern with portable pressure ventilators is the potential for rebreathing of carbon dioxide. Despite these issues, pressure support ventilation has been used successfully for noninvasive ventilation in thousands of patients with acute respiratory failure.

Aerosol delivery during mechanical ventilation

Aerosols can be delivered during mechanical ventilation using either a nebulizer or MDI. The MDI is the most efficient method of aerosol delivery, whereas the greatest absolute amount of drug delivery is with the nebulizer.

Analysis of mitochondrial antigens reveals inner membrane succinate dehydrogenase flavoprotein subunit as autoantigen to antibodies in anti-M7 sera

The role of mitochondrial proteins as antigens to antibodies of anti-M7 sera was analysed by flavin fluorescence, one- and two-dimensional Western blots and blue native gel electrophoresis. Flavin fluorescence of succinate dehydrogenase (SucDH, complex II of the respiratory chain) of rat liver inner mitochondrial membranes correlated with the immunoreactivity of a representative anti-M7 myocarditis serum. Antigens of isolated bovine heart mitochondria reacting with antibodies of myocarditis serum on two-dimensional Western blots were identified by MALDI-TOF and NanoESI mass spectrometry as myosin heavy chain beta and as dihydrolipoamide dehydrogenase of the mitochondrial 2-oxoacid dehydrogenase complexes. The SucDH-flavoprotein was not resolved as a discrete protein spot on two-dimensional polyacrylamide gels. However, separation of the rat liver inner mitochondrial membrane complexes by blue native gel electrophoresis followed by Western blotting, and Western blots of purified Escherichia coli SucDH complex revealed that anti-M7 sera contained antibodies directed against the SucDH-flavoprotein subunit.

Marrow stromal cells form guiding strands in the injured spinal cord and promote recovery

Marrow stromal cells (MSC) can be expanded rapidly in vitro and differentiated into multiple mesodermal cell types. In addition, differentiation into neuron-like cells expressing markers typical for mature neurons has been reported. To analyze whether such cells, exposed to differentiation media, could develop electrophysiological properties characteristic of neurons, we performed whole-cell recordings. Neuron-like MSC, however, lacked voltage-gated ion channels necessary for generation of action potentials. We then delivered MSC into the injured spinal cord to study the fate of transplanted MSC and possible effects on functional outcome in animals rendered paraplegic. MSC given 1 week after injury led to significantly larger numbers of surviving cells than immediate treatment and significant improvements of gait. Histology 5 weeks after spinal cord injury revealed that MSC were tightly associated with longitudinally arranged immature astrocytes and formed bundles bridging the epicenter of the injury. Robust bundles of neurofilament-positive fibers and some 5-hydroxytryptamine-positive fibers were found mainly at the interface between graft and scar tissue. MSC constitute an easily accessible, easily expandable source of cells that may prove useful in the establishment of spinal cord repair protocols.

High-frequency ventilation design and equipment issues

Various technical approaches to high-frequency ventilation are available. Of these, HFOV is used most commonly. As high-frequency ventilation becomes increasingly used in the care of adult patients, the technical issues related to this therapy will become increasingly important.

Ventilator modes used in weaning

Weaning techniques include spontaneous breathing trials (SBTs), pressure-support ventilation (PSV), and synchronized intermittent mandatory ventilation (SIMV). SBTs can be conducted using one of several approaches, including T-piece breathing, low-level continuous positive airway pressure, low-level PSV, or setting the ventilator to flow-triggering with no pressure applied to the airway. The SBT can be used as a method to identify extubation readiness or as a weaning technique in which the duration of the trial is gradually increased over time. With pressure-support weaning, the level of pressure support is gradually reduced over time. With weaning using SIMV, the mandatory rate setting on the ventilator is gradually reduced. Randomized controlled trials have reported the poorest weaning outcomes using SIMV. Although new ventilator modes have been introduced to facilitate weaning, to date there is no evidence to support the use of these modes. Noninvasive positive-pressure ventilation also has been reported to facilitate weaning, but the ability to generalize these findings remains to be determined.

CD40/154 blockade and rejection of islet allografts in the streptozotocin and autoimmune diabetic rat

Islet transplantation in children with autoimmune diabetes will require immunosuppression that has minimal toxicity and side-effects, and overcomes the barrier of autoimmunity. Since antibodies directed against the CD40/154 co-stimulatory pathway may meet these criteria, we have tested the ability of hamster antirat CD154 (AH.F5, Biogen) to prevent rejection of renal subcapsular islet allografts in streptozotocin (STZ) or autoimmune (AUTO) diabetic diabetes-resistant biobreeding (DRBB) rats. STZ diabetic rats that received anti-CD154 at 15 mg/kg per dose but not 10 mg/kg per dose did not have evidence of rejection until about 80-120 d post-transplantation, by which time antibody concentrations had returned to undetectable levels. Rats retreated with anti-CD154 before recurrence of diabetes had a prolonged period of disease-free survival. Most of these rats had recurrence following a spleen cell challenge. In contrast, AUTO diabetic DRBB rats treated with anti-CD154 had recurrence of diabetes between 7 and 12 d following transplantation of the Dark Agouti (DA) islets. In a separate set, AUTO diabetic rats that received a simultaneous islet isograft, islet allograft and thyroid allograft had focal accumulation of lymphocytes at the periphery of the isograft, while the islet and thyroid allografts had diffuse infiltration with lymphocytes and destruction of tissue with no residual staining for glucagon. Therefore, autoimmunity adds an additional barrier to islet allotransplantation that is not overcome with CD40/154 blockade in an animal model that closely parallels autoimmune diabetes in humans. The results indicate the importance of testing regimen of islet transplantation in animal models of autoimmune diabetes.

Interaction of GM(1) glycolipid in phospholipid monolayers with wheat germ agglutinin: effect of phospholipidic environment and subphase

Mixed monolayers of GM(1) glycolipid and stearoyl-oleoyl-phosphatidylcholine (SOPC) or dipalmitoyl-phosphatidycholine (DPPC) phospholipids were studied by surface pressure measurements. The effects induced by GM(1) on the mean molecular areas of mixtures and DPPC phase transition were followed for GM(1) concentrations ranging from 1 to 20 mol.%. Under our experimental conditions, one main parameter influencing the behavior of phospholipid-GM(1) monolayers is the ionic strength of the subphase. Mixed monolayers are in a more expanded state on buffer than on pure water. This could be due to a change of GM(1) orientation at the interface. The interaction of wheat germ agglutinin (WGA), a lectin recognizing specifically GM(1), with these monolayers was quantified in terms of the Gibbs equation. Specific WGA-GM(1) interactions are clearly reduced in the presence of DPPC as compared with SOPC, probably because of the higher packing density of these monolayers. Phospholipid-GM(1) monolayers could also undergo some rearrangements induced by WGA binding.

Identification of tyrosine phosphorylation sites on 3-phosphoinositide-dependent protein kinase-1 and their role in regulating kinase activity

3-Phosphoinositide-dependent protein kinase-1 (PDK1) plays a central role in signal transduction pathways that activate phosphoinositide 3-kinase. Despite its key role as an upstream activator of enzymes such as protein kinase B and p70 ribosomal protein S6 kinase, the regulatory mechanisms controlling PDK1 activity are poorly understood. PDK1 has been reported to be constitutively active in resting cells and not further activated by growth factor stimulation (Casamayor, A., Morrice, N. A., and Alessi, D. R. (1999) Biochem. J. 342, 287-292). Here, we report that PDK1 becomes tyrosine-phosphorylated and translocates to the plasma membrane in response to pervanadate and insulin. Following pervanadate treatment, PDK1 kinase activity increased 1.5- to 3-fold whereas the activity of PDK1 associated with the plasma membrane increased approximately 6-fold. The activity of PDK1 localized to the plasma membrane was also increased by insulin treatment. Three tyrosine phosphorylation sites of PDK1 (Tyr-9 and Tyr-373/376) were identified using in vivo labeling and mass spectrometry. Using site-directed mutants, we show that, although phosphorylation on Tyr-373/376 is important for PDK1 activity, phosphorylation on Tyr-9 has no effect on the activity of the kinase. Both of these residues can be phosphorylated by v-Src tyrosine kinase in vitro, and co-expression of v-Src leads to tyrosine phosphorylation and activation of PDK1. Thus, these data suggest that PDK1 activity is regulated by reversible phosphorylation, possibly by a member of the Src kinase family.

Stable transformation of sunflower (Helianthus annuus L.) using a non-meristematic regeneration protocol and green fluorescent protein as a vital marker

Stable transformation of sunflower was achieved using a non-meristematic hypocotyl explant regeneration protocol of public inbred HA300B. Uniformly transformed shoots were obtained after co-cultivation with Agrobacterium tumefaciens carrying a gfp (green fluorescent protein) gene containing an intron that blocks expression of gfp in Agrobacterium. Easily detectable, bright green fluorescence of transformed tissues was used to establish an optimal regeneration and transformation procedure. By Southern blot analysis, integration of the gfp and nptll genes was confirmed. Stable transformation efficiency was 0.1%. From 68 T1 plants analyzed, 17 showed transmission of transgene DNA and 15 of them contained the intact gfp gene. Expression of gfp was detected in 10 T1 plants carrying the intact gfp gene using a fluorimetric assay or western blot analysis. Expression of the nptll gene was confirmed in 13 T1 plants. The transformation system enables the rapid transfer of agronomically important genes.

Repetitive high-pressure recruitment maneuvers required to maximally recruit lung in a sheep model of acute respiratory distress syndrome

OBJECTIVE

To compare the effects of two different recruitment maneuvers repeated multiple times on gas exchange lung injury, hemodynamic, and lung mechanics.

DESIGN

Randomized prospective comparison.

SETTINGS

Animal research laboratory.

SUBJECT

Nineteen fasted Hampshire sheep.

INTERVENTIONS

In 15 27-kg sheep with saline lavage lung injury, we compared the effects of two recruitment maneuvers: 40 cm H2O continuous positive airway pressure for 60 secs and 40 cm H2O positive end-expiratory pressure with 20 cm H2O pressure control, rate 10 breaths/min, inspiratory to expiratory ratio 1:1 for 2 mins. Each recruitment maneuver was repeated four times, every 30 mins after a 30-sec ventilator disconnection. An additional group received no recruitment maneuvers. Animals were assigned randomly to the three groups and ventilated with 20 cm H2O positive end-expiratory pressure, pressure control 15 cm H2O, rate 20 breaths/min, inspiratory to expiratory ratio 1:1, and Fio2 1.0 between recruitment maneuver periods.

MEASUREMENTS AND MAIN RESULTS

Significant and marked increases in Pao2 were observed in the pressure control recruitment maneuver group but only after the second recruitment maneuver. In both the control group and continuous positive airway pressure groups, Pao2 did not significantly increase after any recruitment maneuver compared with baseline injury. There was a significant decrease in cardiac output immediately after some continuous positive airway pressure recruitment maneuvers and a significant increase in mean pulmonary artery pressure in both continuous positive airway pressure and pressure control groups immediately after recruitment maneuvers, but these changes resolved within 10 mins. There were no marked histologic differences between groups and no volutrauma.

CONCLUSION

In this model, maximal lung recruitment was obtained with 40 cm H2O positive end-expiratory pressure and 20 cm H2O pressure control applied repetitively every 30 mins for 2 mins without physiologic or histologic harm. Multiple recruitment maneuvers in some animals were required for maximum effect.

Directed proteomics identifies a plant-specific protein rapidly phosphorylated in response to bacterial and fungal elicitors

The perception of microbial signal molecules is part of the strategy evolved by plants to survive attacks by potential pathogens. To gain a more complete understanding of the early signaling events involved in these responses, we used radioactive orthophosphate to pulse-label suspension-cultured cells of Arabidopsis in conjunction with two-dimensional gel electrophoresis and mass spectrometry to identify proteins that are phosphorylated rapidly in response to bacterial and fungal elicitors. One of these proteins, AtPhos43, and related proteins in tomato and rice, are phosphorylated within minutes after treatment with flagellin or chitin fragments. By measuring (32)P incorporation into AtPhos43 immunoprecipitated from extracts of elicitor-treated hormone and defense-response mutants, we found that phosphorylation of AtPhos43 after flagellin treatment but not chitin treatment is dependent on FLS2, a receptor-like kinase involved in flagellin perception. Induction by both elicitors is not dependent on salicylic acid or EDS1, a putative lipase involved in defense signaling.

Characterization of a high-voltage-activated IA current with a role in spike timing and locomotor pattern generation

Transient A-type K+ channels (I(A)) in neurons have been implicated in the delay of the spike onset and the decrease in the firing frequency. Here we have characterized biophysically and pharmacologically an I(A) current in lamprey locomotor network neurons that is activated by suprathreshold depolarization and is specifically blocked by catechol at 100 microM. The biophysical properties of this current are similar to the mammalian Kv3.4 channel. The role of the I(A) current both in single neuron firing and in locomotor pattern generation was analyzed. The I(A) current facilitates Na+ channel recovery from inactivation and thus sustains repetitive firing. The role of the I(A) current in motor pattern generation was examined by applying catechol during fictive locomotion induced by N-methyl-d-aspartate. Blockade of this current increased the locomotor burst frequency and decreased the firing of motoneurons. Although an alternating motor pattern could still be generated, the cycle duration was less regular, with ventral roots bursts failing on some cycles. Our results thus provide insights into the contribution of a high-voltage-activated I(A) current to the regulation of firing properties and motor coordination in the lamprey spinal cord.