[The proximally pedicled anterolateral thigh flap for reconstruction of complex soft tissue wounds of the hip and caudal trunk region]. / Die proximal gestielte Anterior-lateral-thigh-Lappenplastik zur Rekonstruktion komplexer Weichteilwunden der Hüft- und kaudalen Rumpfregion.

INTRODUCTION: Groin and lower trunk defects are common problems, especially for elderly patients. While groin defects are often due to prior vascular interventions, trochanteric defects are mainly caused by pressure sores. Plastic reconstructive methods are manifold; however, the pedicled anterolateral thigh (ALT) flap is supposed to be reliable with sustainable results. OBJECTIVE: We present our experiences using the pedicled ALT flap for soft tissue reconstruction in patients with large wounds of the medial and lateral proximal thigh. MATERIALS AND METHODS: A total of 16 patients with groin and lower trunk defects due to prior vascular surgery or pressure sores received locoregional soft tissue reconstruction using a proximal pedicled ALT flap. Patient characteristics, defect size, surgery time, clinical outcome and complication rate were assessed. RESULTS: With the exception of two cases, sufficient soft tissue reconstruction was achieved. In all, 81,3% of patients were categorized as ASA (American Society of Anesthesiologists) 3. The average duration of surgery was 149 min. Length of stay was 18,3 days. A total of 31% needed revision surgery due to limited wound healing problems. Two patients died. All patients showed healed wound conditions when they were discharged. CONCLUSION: The proximal pedicled ALT-flap is a reliable method for soft tissue reconstruction in groin and lower trunk defects. This reconstructive procedure enables reliable wound closure, especially in elderly patients with substantially reduced general health condition.

Prednisolone but not selenium and rtPA reduces edema and improves angiogenesis after burn in mice.

OBJECTIVE: Despite dramatic improvements in burn care, the major part of the therapy of thermal injuries remains symptomatical in nature. A targeted approach to accelerate angiogenesis and woundhealing and reduce edema formation remains to be found. We therefore aimed to investigate the impact of anti-inflammatory, anti-coagulative and thrombolytic agents on microcirculation after thermal injuries on the mentioned parameters. METHODS: Full thickness burns were inflicted on the ears of hairless mice (n=48). The effects of five intraperitoneal injections of either recombinant tissue plasminogen activator (rtPA), selenium, prednisolone or sodium chloride on microcirculation, edema formation, leukocytes and angiogenesis were investigated over a 13 day period using intravital fluorescent microscopy. RESULTS: Prednisolone slightly improved angiogenesis (100.0% day 0 vs. 91.4% non-perfused area on day 1 post burn, p<0.05) and reduced edema formation (93.3% vs. 123.1% control on day 3, p<0.05). The rtPA-group showed the highest number of sticking leukocytes up to day 7 post burn (233%, 265%, 254% on days 1, 3, and 7, p<0.05 compared to baseline). A post-traumatic expansion of the non perfused area could only be observed in the selenium group (100.0% day 0, 103.1% day 1 post burn). In addition, selenium caused an increase of rolling leukocytes over the complete observation time. CONCLUSION: The often described positive influences of selenium for the treatment of burn patients could not be confirmed, on the contrary we found a post-traumatic expansion of the non perfused area and an increase of leukocytes in this group. The expectations to rtPA did not fulfill. Prednisolone improved angiogenesis and reduced the edema formation, both Parameters are essential for wound healing and survival of burned patients.

Long-term behavior of double crown retained dentures with metal and metal-free secondary crowns and frameworks made of Vectris(©) on all-ceramic primary crowns: a prospective, randomized clinical trial up to 14 years.

OBJECTIVES: This prospective randomized clinical trial aimed to evaluate the long-term behavior of metal-free double crown retained dentures with secondary crowns and dental frameworks made of the fiber-reinforced composite Vectris(©) on all-ceramic primary crowns (IPS Empress 2(©)) over a period of up to 14 years and to subsequently evaluate patient satisfaction. For the control group, electroplated gold copings and metal frameworks were used. MATERIALS AND METHODS: A total of 29 patients were treated with a total of 37 prostheses on 165 primary crowns. Of these 37 prostheses, 27 were allotted to the control group and 10 to the test group. The mean observation time was 91 ± 57 months; patient satisfaction surveys were conducted over 77 ± 59 months. RESULTS: Success rates in both groups were compared using Kaplan-Meier survival curves and log-rank test. Up to about 3 years, both types of prostheses exhibited similar success rates. Afterwards, a massive decrease in the Vectris(©) curve could be noted, whereas the metal curve dropped only slightly. This difference was also statistically significant (p = 0.032361). There was a comparable susceptibility to damages in both groups: 88.9 % (control) and 90 % (test), respectively, of the prostheses had to be repaired within the period of investigation (p = 0,121). Damages of the Vectris(©) secondary crowns could be detected significantly more often compared to the electroformed gold copings (p < 0.00005). Patient satisfaction with the restorations was comparably high in both groups. CONCLUSION: Metal-free secondary crowns and denture frameworks made with the glass fiber-reinforced composite material Vectris(©) showed a lower survival rate than the electroplated gold copings and metal frameworks. Primary crowns made of IPS Empress 2(©) had insufficient stability. Exclusively high-strength zirconia ceramics should be recommended for this indication. CLINICAL RELEVANCE: Both clinical and statistical data indicated the superiority of the restorations made with electroplated secondary crowns and metal framework. Therefore, the use of Vectris(©) cannot be recommended for the fabrication of double crown retained removable dentures as permanent restorations.

Influence of ISDN, L-NAME and selenium on microcirculation, leukocyte endothelium interaction and angiogenesis after frostbite.

BACKGROUND: The body of knowledge regarding the different facets of frostbite injury continues to expand. However, beside the administration of physiological saline, local rewarming, local disinfection and symptomatic medications, today no causal therapy is known which would accelerate angiogenesis and wound healing. The aim of this study was to investigate the influences of dilative acting drugs on microcirculation, angiogenesis and leukocyte behavior. MATERIALS AND METHODS: Ears of male hairless mice (n=40) were inflicted with full thickness frostbites using a cold air jet. Then the affects of four intraperitoneal injections of isosorbitdinitrate (ISDN, n=10), l-nitroarginine-methyl-ester (l-NAME, n=10), selenium (n=10) or sodium chloride (n=10; each administered to one of four corresponding study groups), on microcirculation, leukocyte-endothelial interaction and angiogenesis were investigated over a 12-day period using intravital fluorescent microscopy. RESULTS: Angiogenesis was most improved by ISDN (36.8 vs. 54.5% non-perfused area on day 3, 3.9 vs. 17.0% on day 7 compared to selenium, p<0.006). Venular diameter was most significantly dilated in the ISDN-group, l-NAME showed significantly decreased diameter over the complete time of 12 days. ISDN had positive influences on edema formation, which was significantly reduced compared to control (27% lower values compared to control; p=0.007 on day 3). The l-NAME-group showed the significant highest leukocyte-adhesion compared to control on days 7 and 12 (53% resp. 58% higher, p<0.006). CONCLUSION: Overall, out of all the drugs tested, ISDN improved angiogenesis, dilated venules and decreased edema formation and therefore seems to have the greatest positive impact on these crucial parameters after frostbite injury.

Repetitive extracorporeal shock wave applications are superior in inducing angiogenesis after full thickness burn compared to single application.

OBJECTIVE: Burn wounds remain a challenge due to subsequent wound infection and septicemia, which can be prevented by acceleration of wound healing. The aim of the study was to analyze microcirculation and leukocyte endothelium interaction with particular focus on angiogenesis after full-thickness burn using three different repetitions of low energy shock waves. METHODS: Full-thickness burns were inflicted to the ears of hairless mice (n=44; area: 1.6±0.05 mm2 (mean±SEM)). Mice were randomized into four groups: the control group received a burn injury but no shock waves; group A received ESWA (0.03 mJ/mm2) on day one after burn injury; group B received shock waves on day one and day three after burn injury; group C ESWA on day one, three and seven after burn injury. Intravital fluorescent microscopy was used to assess microcirculatory parameters, angiogenesis and leukocyte interaction. Values were obtained before burn (baseline value) immediately after and on days 1, 3, 7 and 12 after burn. RESULTS: Shock-wave treated groups showed significantly accelerated angiogenesis compared to the control group. The non-perfused area (NPA) is regarded as a parameter for angiogenesis and showed the following data on day 12 2.7±0.4% (group A, p=0.001), 1.4±0.5% (group B, p<0.001), 1.0±0.3% (group C, p<0.001), 6.1±0.9% (control group). Edema formation is positively correlated with the number of shock wave applications: day 12: group A: 173.2±9.8%, group B: 184.2±6.6%, group C: 201.1±6.9%, p=0.009 vs. control: 162.3±8.7% (all data: mean±SEM). CONCLUSION: According to our data shock waves positively impact the wound healing process following burn injury. Angiogenesis showed significantly improved activity after shock wave application. In all three treatment groups angiogenesis was higher compared to the control group. Within the ESWA groups, double applications showed better results than single application and three applications showed better results than single or double applications.

Extracorporeal shock waves improve angiogenesis after full thickness burn.

OBJECTIVE: Extensive wounds of burn patients remain a challenge due to wound infection and subsequent septicemia. We wondered whether extracorporeal shock wave application (ESWA) accelerates the healing process. The aim of the study was to analyze microcirculation, angiogenesis and leukocyte endothelium interaction after burns by using ESWA with two types of low intensity. METHODS: Full-thickness burns were inflicted to the ears of hairless mice (n=51; area: 1.3 mm(2)). The mice were randomized into five groups: (A) low-energy shock waves after burn injury (0.04 mJ/mm(2)); (B) very low-energy shock waves after burn injury (0.015 mJ/mm(2)); (C) mice received burns but no ESWA (control group); (D) mice without burn were exposed to low-energy shock waves; (E) mice without burns and with no shock wave application. Intravital fluorescent microscopy was used to assess microcirculatory parameters, angiogenesis and leukocyte behavior. ESWA was performed on day 1, 3 and 7 (500 shoots, 1 Hz). Values were obtained straight after and on days 1, 3, 7 and 12 post burn. RESULTS: Group A showed accelerated angiogenesis (non-perfused area at day 12: 5.3% vs. 9.1% (group B) and 12.6% (group C), p=0.005). Both shock wave groups showed improved blood flow after burn compared to group C. Shock waves significantly increased the number of rolling leukocytes compared to the non-ESWA-treated animals (group D: 210.8% vs. group E: 83.3%, p=0.017 on day 7 and 172.3 vs. 90.9%, p=0.01 on day 12). CONCLUSION: Shock waves have a positive effect on several parameters of wound healing after burns, especially with regard to angiogenesis and leukocyte behaviour. In both ESWA groups, angiogenesis and blood flow outmatched the control group. Within the ESWA groups the higher intensity (0.04 mJ/mm(2)) showed better results than the lower intensity group. Moreover, shock waves increased the number of rolling and sticking leukocytes as a part of an improved metabolism.

Guidelines for palliative surgery of cholangiocarcinoma.

The aims of the guidelines are to help assess the evidence for palliation surgery in patients with cholangiocarcinoma (CCA). The guidelines are classified in accordance with the location of the primary lesion, i.e. intrahepatic, hilar, and distal. They are based on comprehensive literature surveys, including results from randomized controlled trials, systematic reviews and meta-analysis, and cohort, prospective, and retrospective studies. Intrahepatic CCA, i.e. resection of lymph-node-positive tumors and R1/R2 resections have not been shown to provide survival benefit: Evidence levels: 2b, 4; Recommendation grade C. Hilar CCA: R1 resection is justified as a very efficient palliation. Non-surgical biliary stenting is the first choice of palliative biliary drainage. Distal CCA: Resection of lymph-node-positive tumours and R1/R2 resections should be performed. Non-surgical stenting is regarded as the first choice of palliation for patients with short life expectancy. For patients with longer projected survival, surgical bypass should be considered. Palliative resections have a relevant beneficial impact on the outcome of patients with distal and hilar CCA. Non-surgical stenting is the first choice of palliative biliary drainage for patients with hilar CCA and for those with distal CCA and short life expectancy. For patients with distal CCA and longer projected survival, surgical bypass should be considered.

Sirolimus improves early microcirculation, but impairs regeneration after pancreatic ischemia-reperfusion injury.

Ischemia and reperfusion injury remains a relevant problem in clinical pancreas transplantation. We investigated the effect of sirolimus (SRL) in a rodent model of 90-min warm pancreatic ischemia. Four groups were studied: (1) sham surgery and vehicle; (2) sham surgery and SRL; (3) warm ischemia and vehicle; (4) warm ischemia and SRL. SRL (1.5 mg/kg/day) and vehicle were administered intraperitoneally for 3 days prior to surgery until the animals were killed. Microcirculation was assessed immediately after reperfusion by means of intravital fluorescence microscopy. Histopathological injury, apoptosis, proliferation and biochemical parameters were analyzed at 2 h, 1 day and 5 days after surgery. Ninety minutes after ischemia, intravital microscopy revealed an improved functional capillary density (p < 0.05) and reduction of adherent leucocytes (p < 0.01) and platelets (p < 0.05) in the SRL-treated group compared to the vehicle-treated controls. In contrast, on day 5 after ischemia, the pancreatic tissue of SRL-treated animals showed a higher grade of histological injury (p < 0.05) and higher rate of apoptotic cells (p < 0.05) than the vehicle controls. In summary, our data indicate that administration of SRL improves microcirculation at a very early stage, but results in an impairment of the recovery phase after pancreatic ischemia-reperfusion injury.

Fusion of small unilamellar vesicles onto laterally mixed self-assembled monolayers of thiolipopeptides.

Monolayers of the thiolipopeptide NH(2)-Cys-Ala-Ser-Ala-Ala-Ser-Ser-Ala-Pro-Ser-Ser-(Myr)Lys(Myr)-OH (III) were formed on gold surfaces by self-assembly, mixed with a lateral spacer of the same peptide composition, NH(2)-Cys-Ala-Ser-Ala-Ala-Ser-Ser-Ala-Pro-Ser-Ser-Lys-OH (I). Different mixing ratios were employed ranging from 0.1 to 1, corresponding to 10-100% thiolipopeptide. These self-assembled monolayers (SAMs) were then exposed to a suspension of liposomes with the aim of forming lipid bilayers as a function of the mixing ratio. A clear optimum with respect to homogeneity and electrical properties of the membranes was obtained in the middle region (0.5) of mixing ratio, as revealed by surface plasmon resonance spectroscopy, impedance spectroscopy, and fluorescence microscopy. The combination of these methods was shown to be a powerful tool, although a true lipid bilayer was not obtained. Instead, vesicle adsorption was shown to be the predominant process, and FRAP (fluorescence recovery after photobleaching) measurements showed that the films were not fluid on the micrometer length scale.

Fracture characteristics of carbon fibre, ceramic and non-palladium endodontic post systems at monotonously increasing loads.

A carbon fibre post system, three non-palladium and one palladium metal post systems, two ceramic post systems, and a metal post system with a ceramic core were studied in vitro. The control group consisted of root-filled test teeth without posts. The test teeth were identical artificial roots of an upper central incisor made from a posterior composite whose module of elasticity was similar to that of natural dentine. All posts were cemented in the roots using Panavia 21 TC. Subsequently, standardized full crowns were cemented onto all roots. On a universal testing machine, the test teeth were loaded palatally at monotonously increasing loads until root fracture. The highest mean fracture loads were found for the carbon fibre post system (312.5 +/- 58.8 N). The fracture load of non-palladium metal posts (242.3-300.4 N) did not differ significantly from that of the Perma-dor post (265.9 N), which does contain palladium. Values of 300.3 +/- 89.3 N (aluminium oxide ceramics) and 193.5 +/-57.0 N (zirconia ceramics) were found for the ceramic posts. The control group exhibited a fracture load of 228.8 +/- 35.7 N. The mean distance between the vestibular end of the fracture gap and the point of force application was between 10.1 +/- 2.3 and 14.7 +/- 1.2 mm.

Laboratory strength of glass ionomer and zinc phosphate cements.

PURPOSE: The present in vitro study examined 3 mechanical properties, namely compressive, flexural, and diametral tensile strength, of various commercially available cements and core materials as a function of time after mixing. MATERIALS AND METHODS: The examined materials were 2 cermet cements (Ketac Silver [ESPE, Seefeld, Germany] and Chelon Silver [ESPE]), 1 metal-reinforced glass ionomer cement (Miracle Mix [GC Dental Industrial Corp, Tokyo, Japan]), 2 conventional glass ionomer cements (Ketac Bond [ESPE] and Ketac Cem [ESPE]), 1 standard cure zinc phosphate cement (Harvard Cement [Richter and Hoffmann, Berlin, Germany]), and 1 zinc phosphate cement with the addition of 30% silver amalgam alloy powder (Harvard Cement 70% with Dispersalloy 30% [Richter and Hoffmann/Johnson and Johnson, East Windsor, NJ]). Properties were measured using a universal testing machine at 15 minutes, 1 hour, and 24 hours after first mixing. RESULTS: Compressive strengths varied widely between the 3 times of measurement from 5.8 +/- 6.6 MPa for Ketac Cem to 144.3 +/- 10.2 MPa for Ketac Silver. Twenty-four hours after mixing, the Bonferroni test showed significant (p

Advanced biomaterials used for a new telescopic retainer for removable dentures.

Removable dentures supported by cast-metal telescopic crowns often exhibit an unpredictable increase or decrease in retentive force after being in clinical use for some time. The objective of the present in vitro study was to develop a new retainer for removable dentures and to evaluate its tribological properties. The new retainer is based on a tapered crown design and consists of a conical all-ceramic abutment crown and a coping made of electroplated gold. It was compared with conventional telescopic retainers made of cast metal. There were 30 specimens in groups of equal size by material used (abutment crown/coping): Group 1, gold/gold; Group 2, titanium/titanium; Group 3, ceramic/electroplated gold. Each specimen consisted of 2 conical-shaped abutment crowns (alpha =4 degrees; h = 6 mm; O(base) = 4,5 mm); their copings were rigidly connected at 25 mm intervals. Retentive forces were measured with a universal testing machine following axial loading to 5-400 N. Wear was simulated by 500-100, 000 joining and separating cycles in the presence of artificial saliva. Metallographic cross-sections were made to evaluate the specimens' fit and surfaces with an SEM. Retentive forces in Groups 1 and 2 increased with load, exhibiting nondirectional changes after induced wear. Sometimes the alloys' functional surfaces showed considerable tracks of wear. Neither load nor wear had any effect on Group 3 retentive forces (mean(force) = 5.03 N). The functional ceramic and gold surfaces showed no traces of wear and the best fit (median(gap) = 4.9 microm). Replacing cast metals by ceramics and electroplated gold results in retainers with clinically advantageous tribological effects, implying, in particular, high wear resistance.

Advanced biomaterials used for a new telescopic retainer for removable dentures.

Telescopic retainers with conical ceramic abutment crowns and electroplated gold copings define a new retainer for removable dentures exhibiting favorable tribological properties that could offer clinical advantages. The objective of this study was to evaluate the clinical effects of this retainer. To do so, a novel treatment modality was developed based on intraoral bonding of the copings to the framework in order to be able to realize, in a clinical setting, the retainer function based on a precision fit. A total of 32 patients wearing 33 dentures (16 mandibular, 17 maxillary; period of risk [months]: minimum = 3; maximum = 58; mean = 27.6), supported by 147 abutments (83 natural teeth, 64 implants) with ceramic abutment crowns (IPS Empress 1, IPS Empress 2, InCeram, Procera, CerAdapt; CeraBase) were followed at 6-month intervals. The ceramic abutment crowns showed low plaque accumulation (mean PI = 17.3%). The gingival tissues around natural abutments were generally free of inflammation; so was the mucosa around the implants (mean SBI = 4.9%). Denture adhesion and occlusion did not change, and there were no rocking movements. The mobility (as determined by Periotest) of 29 teeth was reduced in a highly significant manner within 6 months (t test, p < 0.001). Osseointegration was preserved for all implants. One abutment loosened. Six Empress 1 ceramic copings failed (94.6% Kaplan-Meier survival rate), and one abutment tooth was lost (99.2% survival rate). All patients reported problem-free handling, no rocking movements, and constant adhesion. The adhesive strength of one denture was too low at insertion. 94% of the patients experienced no problems with oral hygiene. The retainer examined has relevant clinical advantages and meets geriatric requirements for removable dentures.

The Procera AllCeram system.

The Procera AllCeram system is indicated for manufacturing all-ceramic crowns for single-tooth restorations in the anterior and posterior regions. In addition, it is possible to create metal-free superstructures on CeraOne abutments from the Brånemark implant system or crowns on individually prepared aluminum oxide abutments (CerAdapt). The Procera copings, which are manufactured using computer-aided design/manufacturing technology, are characterized by very good mechanical properties. Ceramic veneers tailored to the copings offer excellent esthetics, favorable abrasion behavior, and an ideal surface structure for non-inflammatory apposition of the periodontal or periimplant tissues. The present article offers an overview of previous scientific studies, describes clinical and laboratory procedures, and presents case reports.

Success rates for two different types of post-and-cores.

The objective of our follow-up study was to evaluate the success of two different types of partially prefabricated post-and-core systems following crown placement. Two hundred and thirty-seven Permador posts and 49 Radix posts were evaluated clinically. Radiological follow-up was performed for 230 Permador posts and 47 Radix posts. The restorations had been in situ for an average of 3.9 years (Permador posts) and 2.3 years (Radix posts), respectively. Root canal fillings were evaluated as to their length, their homogeneity and their flushness with the walls of the root canal. The post-and-cores were evaluated for their orientation in the root canal and for the length of the inserted post relative to the length of the root. The position of the post was classified as centric in 78.0% of the restorations followed, and eccentric in 19.5%, while 2.5% showed a root perforation. The minimal requirement that the length of the post-and-core should at least be equal to the length of the clinical crown was met in 85% of the cases. Eighteen (6.3%) of the 286 teeth examined had to be extracted. There were significant correlations between insertion periods, horizontal bone loss, length of the root canal filling, and position of the post on one hand and tooth loss on the other.

Temperature response in the pulpal chamber during ultrahigh-speed tooth preparation with diamond burs of different grit.

STATEMENT OF PROBLEM: Ultrahigh-speed tooth preparation can traumatize the hard dental tissues and the dental pulp. PURPOSE: This in vitro study examined the relationship between different grits of diamond burs on the temperature response within a pulpal chamber during tooth preparation with a turbine. MATERIAL AND METHODS: Newly extracted, undamaged third molars were secured by a rapid-tensioning device mounted on an air-supported slide. NiCrNi thermocouples were inserted apically and used to determine the temperature within a pulpal chamber. The grinding tests used cylindrical fine, coarse, and ultracoarse diamond burs. RESULTS: The maximal temperature elevation within the pulp was 3.2 degrees C, and the most pronounced rise in temperature occurred with ultracoarse burs. Temperature increases in the pulpal chambers and grinding times or temperatures of the cooling water were approximately proportional. Residual dentinal thickness was inversely proportional to temperature elevation within the pulpal chamber. CONCLUSIONS: This study demonstrated that coarse diamond burs resulted in more pronounced temperature increases within the pulpal chamber during tooth preparation. In addition, the benefit of short intervals between grinding steps and a cooling water temperature between 30 degrees C and 32 degrees C was confirmed. A cooling temperature of 38 degrees C to 43 degrees C did not afford actual cooling.

Contamination-free and automated composition of a reaction mixture for nucleic acid amplification using a capillary electrophoresis apparatus.

The acceptance of the polymerase chain reaction (PCR) as an amplification method in molecular diagnostics and the rapid development of capillary electrophoresis (CE) as an analysis method of those PCR products was a reason for us to investigate further integration of those two techniques. Using a fused-silica capillary as a pipette we were able to compose a PCR mixture in the CE apparatus. Because a capillary can be thoroughly rinsed and the CE apparatus is a closed system, the risk of contamination and therefore the occurrence of false positive results is minimized. The fact that a CE system can be fully automated contributes to a more reproducible and standardized PCR composition protocol.

Volumetric object modeling for surgical simulation.

Surgical simulation has many applications in medical education, surgical training, surgical planning and intra-operative assistance. However, extending current surface-based computer graphics methods to model phenomena such as the deformation, cutting, tearing or repairing of soft tissues poses significant challenges for real-time interactions. This paper discusses the use of volumetric methods for modeling complex anatomy and tissue interactions. New techniques are introduced that use volumetric methods for modeling soft-tissue deformation and tissue cutting at interactive rates. An initial prototype for simulating arthroscopic knee surgery is described which uses volumetric models of the knee derived from 3-D magnetic resonance imaging, visual feedback via real-time volume and polygon rendering, and haptic feedback provided by a force-feedback device.

Brain-derived neurotrophic factor mediates the activity-dependent regulation of inhibition in neocortical cultures.

The excitability of cortical circuits is modulated by interneurons that release the inhibitory neurotransmitter GABA. In primate and rodent visual cortex, activity deprivation leads to a decrease in the expression of GABA. This suggests that activity is able to adjust the strength of cortical inhibition, but this has not been demonstrated directly. In addition, the nature of the signal linking activity to GABA expression has not been determined. Activity is known to regulate the expression of the neurotrophin brain-derived neurotrophic factor (BDNF), and BDNF has been shown to influence the phenotype of GABAergic interneurons. We use a culture system from postnatal rat visual cortex to test the hypothesis that activity is regulating the strength of cortical inhibition through the regulation of BDNF. Cultures were double-labeled against GABA and the neuronal marker MAP2, and the percentage of neurons that were GABA-positive was determined. Blocking spontaneous activity in these cultures reversibly decreased the number of GABA-positive neurons without affecting neuronal survival. Voltage-clamp analysis of inhibitory currents demonstrated that activity blockade also decreased GABA-mediated inhibition onto pyramidal neurons and raised pyramidal neuron firing rates. All of these effects were prevented by incubation with BDNF during activity blockade, but not by neurotrophin 3 or nerve growth factor. Additionally, blockade of neurotrophin signaling mimicked the effects of activity blockade on GABA expression. These data suggest that activity regulates cortical inhibition through a BDNF-dependent mechanism and that this neurotrophin plays an important role in the control of cortical excitability.