The Contribution of the Left Phrenic Nerve to Innervation of the Esophagogastric Junction.

The contribution of the left phrenic nerve to innervation of the esophagogastric junction. The esophagogastric junction is part of the barrier preventing gastroesophageal reflux. We have investigated the contribution of the phrenic nerves to innervation of the esophagogastric junction in humans and piglets by dissecting 30 embalmed human specimens and 14 piglets. Samples were microdissected and nerves were stained and examined by light and electron microscopy. In 76.6% of the human specimens, the left phrenic nerve participated in the innervation of the esophagogastric junction by forming a neural network together with the celiac plexus (46.6%) or by sending off a distinct phrenic branch, which joined the anterior vagal trunk (20%). Distinct left phrenic branches were always accompanied by small branches of the left inferior phrenic artery. In 10% there were indirect connections with a distinct phrenic nerve branch joining the celiac ganglion, from which celiac plexus branches to the esophagogastric junction emerged. Morphological examination of phrenic branches revealed strong similarities to autonomic celiac plexus branches. There was no contribution of the left phrenic nerve or accompanying arteries from the caudal phrenic artery in any of the piglets. The right phrenic nerve made no contribution in any of the human or piglet samples. We conclude that the left phrenic nerve in humans contributes to the innervation of the esophagogastric junction by providing ancillary autonomic nerve fibers. Experimental studies of the innervation in pigs should consider that neither of the phrenic nerves was found to contribute. Clin. Anat. 33:265-274, 2020. © 2019 Wiley Periodicals, Inc.

Interprofessional education in anatomy: Learning together in medical and nursing training.

Teamwork and the interprofessional collaboration of all health professions are a guarantee of patient safety and highly qualified treatment in patient care. In the daily clinical routine, physicians and nurses must work together, but the education of the different health professions occurs separately in various places, mostly without interrelated contact. Such training abets mutual misunderstanding and cements professional protectionism, which is why interprofessional education can play an important role in dismantling such barriers to future cooperation. In this article, a pilot project in interprofessional education involving both medical and nursing students is presented, and the concept and the course of training are described in detail. The report illustrates how nursing topics and anatomy lectures can be combined for interprofessional learning in an early phase of training. Evaluation of the course showed that the students were highly satisfied with the collaborative training and believed interprofessional education (IPE) to be an important experience for their future profession and understanding of other health professionals. The results show that the IPE teaching concept, which combines anatomy and nursing topics, provides an optimal setting for learning together and helps nurses and doctors in training to gain knowledge about other health professionals' roles, thus evolving mutual understanding.

Effects of exogenous surfactant on the non-heart-beating donor lung graft in experimental lung transplantation - a stereological study.

The use of non-heart-beating donor (NHBD) lungs may help to overcome the shortage of lung grafts in clinical lung transplantation, but warm ischaemia and ischaemia/reperfusion injury (I/R injury) resulting in primary graft dysfunction represent a considerable threat. Thus, better strategies for optimized preservation of lung grafts are urgently needed. Surfactant dysfunction has been shown to contribute to I/R injury, and surfactant replacement therapy is effective in enhancing lung function and structural integrity in related rat models. In the present study we hypothesize that surfactant replacement therapy reduces oedema formation in a pig model of NHBD lung transplantation. Oedema formation was quantified with (SF) and without (non-SF) surfactant replacement therapy in interstitial and alveolar compartments by means of design-based stereology in NHBD lungs 7 h after cardiac arrest, reperfusion and transplantation. A sham-operated group served as control. In both NHBD groups, nearly all animals died within the first hours after transplantation due to right heart failure. Both SF and non-SF developed an interstitial oedema of similar degree, as shown by an increase in septal wall volume and arithmetic mean thickness as well as an increase in the volume of peribron-chovascular connective tissue. Regarding intra-alveolar oedema, no statistically significant difference could be found between SF and non-SF. In conclusion, surfactant replacement therapy cannot prevent poor outcome after prolonged warm ischaemia of 7 h in this model. While the beneficial effects of surfactant replacement therapy have been observed in several experimental and clinical studies related to heart-beating donor lungs and cold ischaemia, it is unlikely that surfactant replacement therapy will overcome the shortage of organs in the context of prolonged warm ischaemia, for example, 7 h. Moreover, our data demonstrate that right heart function and dysfunctions of the pulmonary vascular bed are limiting factors that need to be addressed in NHBD.

A novel technique, dynamic intraligamentary stabilization creates optimal conditions for primary ACL healing: a preliminary biomechanical study.

BACKGROUND: Anterior cruciate ligament (ACL) rupture is a common lesion. Current treatment emphasizes arthroscopic ACL reconstruction via a graft, although this approach is associated with potential drawbacks. A new method of dynamic intraligamentary stabilization (DIS) was subjected to biomechanical analysis to determine whether it provides the necessary knee stability for optimal ACL healing. METHODS: Six human knees from cadavers were harvested. The patellar tendon, joint capsule and all muscular attachments to the tibia and femur were removed, leaving the collateral and the cruciate ligaments intact. The knees were stabilized and the ACL kinematics analyzed. Anterior-posterior (AP) stability measurements evaluated the knees in the following conditions: (i) intact ACL, (ii) ACL rupture, (iii) ACL rupture with primary stabilization, (iv) primary stabilization after 50 motion cycles, (v) ACL rupture with DIS, and (vi) DIS after 50 motion cycles. RESULTS: After primary suture stabilization, average AP laxity was 3.2 mm, which increased to an average of 11.26 mm after 50 movement cycles. With primary ACL stabilization using DIS, however, average laxity values were consistently lower than those of the intact ligament, increasing from an initial AP laxity of 3.00 mm to just 3.2 mm after 50 movement cycles. CONCLUSIONS: Dynamic intraligamentary stabilization established and maintained close contact between the two ends of the ruptured ACL, thus ensuring optimal conditions for potential healing after primary reconstruction. The present ex vivo findings show that the DIS technique is able to restore AP stability of the knee.

Implementation of a virtual correlative light and transmission electron microscope.

In the long run, the widespread use of slide scanners by pathologists requires an adaptation of teaching methods in histology and cytology in order to target these new possibilities of image processing and presentation via the internet. Accordingly, we were looking for a tool with the possibility to teach microscopic anatomy, histology, and cytology of tissue samples which would be able to combine image data from light and electron microscopes independently of microscope suppliers. With the example of a section through the villus of jejunum, we describe here how to process image data from light and electron microscopes in order to get one image-stack which allows a correlation of structures from the microscopic anatomic to the cytological level. With commercially available image-presentation software that we adapted to our needs, we present here a platform which allows for the presentation of this new but also of older material independently of microscope suppliers.

Cell-specific expression of human HGF by alveolar type II cells induces remodeling of septal wall tissue in the lung: a morphometric study.

Hepatocyte growth factor (HGF) is involved in development and regeneration of the lungs. Human HGF, which was expressed specifically by alveolar epithelial type II cells after gene transfer, attenuated the bleomycin-induced pulmonary fibrosis in an animal model. As there are also regions that appear morphologically unaffected in fibrosis, the effects of this gene transfer to normal lungs is of interest. In vitro studies showed that HGF inhibits the formation of the basal lamina by cultured alveolar epithelial cells. Thus we hypothesized that, in the healthy lung, cell-specific expression of HGF induces a remodeling within septal walls. Electroporation of a plasmid of human HGF gene controlled by the surfactant protein C promoter was applied for targeted gene transfer. Using design-based stereology at light and electron microscopic level, structural alterations were analyzed and compared with a control group. HGF gene transfer increased the volume of distal air spaces, as well as the surface area of the alveolar epithelium. The volume of septal walls, as well as the number of alveoli, was unchanged. Volumes per lung of collagen and elastic fibers were unaltered, but a marked reduction of the volume of residual extracellular matrix (all components other than collagen and elastic fibers) and interstitial cells was found. A correlation between the volumes of residual extracellular matrix and distal air spaces, as well as total surface area of alveolar epithelium, could be established. Cell-specific expression of HGF leads to a remodeling of the connective tissue within the septal walls in the healthy lung, which is associated with more pronounced stretching of distal air spaces at a given hydrostatic pressure during instillation fixation.

Laser Doppler vibrometric assessment of middle ear motion in Thiel-embalmed heads.

HYPOTHESIS: Thiel-embalmed human whole head specimens represent an alternative model in middle ear research. BACKGROUND: Research into middle ear mechanics and the evaluation of active middle ear implants are generally performed on fresh human temporal bone specimens. A drawback of this method is the limited period during which the specimen can be used before tissue decay begins. Tissue conservation that preserves mechanical properties is desirable. METHODS: Using laser Doppler vibrometry, the movement of the tympanic membrane, stapes, and round window were measured in 23 ears from 15 human whole head specimens embalmed according to Thiel. The ears were acoustically stimulated through the intact external auditory canal. The measurement results were compared with data from the literature. RESULTS: The results were similar to those measured in living subjects and from fresh temporal bones, after excluding measurements with nontypical shapes or low amplitudes, that is, 9% for tympanic membrane, 38% for stapes, and 67% for round window. The best agreement was found for the tympanic membrane (mean difference between 0 and 5.2 dB) and for the stapes measurements (mean difference between 0 and 7.4 dB). Larger differences were found for the round window measurements (mean difference between 3 and 19 dB). For the stimulation levels used, the Thiel specimens behaved linearly in amplitude. The results remained reproducible for more than 20 hours in ambient air, and when the specimen was put back into Thiel solution, the measurements were stable for up to several months between measurements. CONCLUSION: Our results showed that the middle ears of Thiel-embalmed human whole head specimens can be used to study human middle ear mechanics; however, significant differences in some frequencies, particularly at the round window, have to be considered.

Metabolic pathway and distribution of superparamagnetic iron oxide nanoparticles: in vivo study.

BACKGROUND: Experimental tissue fusion benefits from the selective heating of superparamagnetic iron oxide nanoparticles (SPIONs) under high frequency irradiation. However, the metabolic pathways of SPIONs for tissue fusion remain unknown. Hence, the goal of this in vivo study was to analyze the distribution of SPIONs in different organs by means of magnetic resonance imaging (MRI) and histological analysis after a SPION-containing patch implantation. METHODS: SPION-containing patches were implanted in rats. Three animal groups were studied histologically over six months. Degradation assessment of the SPION-albumin patch was performed in vivo using MRI for iron content localization and biodistribution. RESULTS: No SPION degradation or accumulation into the reticuloendothelial system was detected by MRI, MRI relaxometry, or histology, outside the area of the implantation patch. Concentrations from 0.01 µg/mL to 25 µg/mL were found to be hyperintense in T1-like gradient echo sequences. The best differentiation of concentrations was found in T2 relaxometry, susceptibility-sensitive gradient echo sequences, and in high repetition time T2 images. Qualitative and semiquantitative visualization of small concentrations and accumulation of SPIONs by MRI are feasible. In histological liver samples, Kupffer cells were significantly correlated with postimplantation time, but no differences were observed between sham-treated and induction/no induction groups. Transmission electron microscopy showed local uptake of SPIONs in macrophages and cells of the reticuloendothelial system. Apoptosis staining using caspase showed no increased toxicity compared with sham-treated tissue. Implanted SPION patches were relatively inert with slow, progressive local degradation over the six-month period. No distant structural alterations in the studied tissue could be observed. CONCLUSION: Systemic bioavailability may play a role in specific SPION implant toxicity and therefore the local degradation process is a further aspect to be assessed in future studies.

Newly designed, self-coiling catheters for regional anesthesia--an imaging study.

BACKGROUND AND OBJECTIVES: A major concern with the use of continuous peripheral nerve block is the difficulty encountered in placing the catheters close enough to the nerves to accomplish effective analgesia. The aim of this study was to investigate if a self-coiling catheter would remain close to the sciatic nerve once introduced through needles placed under ultrasound guidance and if contrast dye injected through the pigtail catheter made direct contact to the nerves. METHODS: First, Tuohy needles were placed anterior to the sciatic nerves under ultrasound guidance (needle-in-plane/nerve in short-axis approach). Next, the self-coiling catheters were blindly introduced through the needles. A total of 40 catheters were placed; 2 per sciatic nerve in the right and left legs of 10 human cadavers. To detect the exact catheter location, computer tomographic imaging of the legs was performed. Finally, the spread of injected contrast dye in relation to the nerves was assessed by magnetic resonance imaging. RESULTS: There was direct contact of the coil with the nerve in 37 cases. In the remaining cases, the shortest distances from the coil to the nerves were 5, 6, and 7 mm. In all but 1 case, the contrast dye was directly in contact with the nerves. The median circumferential covering of the nerve by contrast dye was 50% (25-interquartile range of 40%). CONCLUSIONS: By using self-coiling catheters, it is possible to blindly introduce the catheter through needles placed under ultrasound guidance with a low risk of catheter misplacement away from the targeted nerves.

Sonographic transvaginal bladder wall thickness: does the measurement discriminate between urodynamic diagnoses?

INTRODUCTION: Measurement of bladder wall thickness (BWT) using transvaginal ultrasound has previously been shown to discriminate between women with confirmed detrusor overactivity and those with urodynamic stress incontinence. Aim of the current study was to determine if vaginally measured BWT correlates with urodynamic diagnoses in a female population. PATIENTS AND METHODS: Between December 2008 and February 2010, adult female consecutive patients undergoing urogynaecologic investigation for lower urinary symptoms were approached to participate in this study. Ethical consent for the current study was obtained. Patients underwent multichannel urodynamics and transvaginal ultrasound measuring the bladder in three location with an emptied bladder. RESULTS: 123 patients were included in the study with a median age of 69 years (range 40-93), median parity of 2 (range 0-3) and a median body mass index of 29.5 kg/m(2) (range 23-38). Urodynamic stress incontinence was diagnosed in 59 patients, DO in 40 and obstruction in 24 cases. Bladder wall thickness was significantly higher in DO patients and in obstruction than in urodynamic stress incontinence. Detrusor pressure at maximum flow rate (pdet/Q(max) ) correlated significantly with BWT. CONCLUSION: Bladder wall thickness shows a significantly positive correlation to pdet/Q(max) and to urodynamic diagnoses of stress incontinence, DO and obstruction.

Sexual function after rectocele repair.

INTRODUCTION: Pelvic organ prolapse is a common condition among women with a prevalence of 11% and may affect the anterior, posterior, or apical compartment with a negative impact on sexual function. AIM: Aim of the current study was to evaluate sexual function before and after surgical rectocele fascial repair in sexually active patients who suffer from symptomatic rectoceles. MAIN OUTCOME MEASURES: Female Sexual Function Index (FSFI) and anatomical outcome after rectocele repair. METHODS: Between December 2000 and December 2009, we asked sexually active female patients who were to undergo rectocele fascial repair for symptomatic rectoceles to participate in this study. The patients were gynecologically examined before and after surgery and prolapse staging was performed using the ICS-Pelvic Organ Prolapse Staging. Patients were asked to fill in the FSFI before surgery and at 6 months follow-up. For statistical analysis, Graph Pad Prism version 5.0 for Windows was used (Graph Pad, La Jolla, CA, USA). Student's t-test was used after normality tests to compare groups and α was set 0.05. RESULTS: Sixty-eight patients were included in this study. Median age was 72 years (range 47-91), median parity of 2 (range 0-3) and median body mass index was 29 kg/m2 (range 23-31). Main complaints preoperatively were painful prolapse feeling (n=52), dyspareunia (n=59), and a feeling of vaginal heaviness (n=39). One patient who had suffered from postoperative infection that resulted in excessive scar tissue of the posterior wall suffered from de novo dyspareunia. Statistical analyses (paired t-test) showed significant improvement for desire (P<0.001), satisfaction (P<0.0001), and pain (P<0.0001) and no significant changes for arousal (P=0.0897), lubrication (P=1), and orgasm (P=0.0893). CONCLUSION: Posterior fascial repair improves some domains of sexual function but not all in sexually active patients with symptomatic rectoceles, and local oestrogene treatment may contribute to this finding.

Aortic arch morphometry in living humans.

Anatomical features of the aortic arch such as its steepness, the take-off angles and the distances between its supra-aortic branches can influence the feasibility and difficulty of interventional and/or surgical maneuvers. These anatomical characteristics were assessed by means of 3D multiplanar reconstruction of thoracic angio-computed tomography scans of 92 living patients (79 males, 13 females, mean age 69.4 ± 9.9 years) carried out for various indications (gross pathology of the thoracic aorta excluded). There was a significant variation of all measured parameters between the subjects - a standard aortic arch (i.e. with all measured parameters within 2 SD) does not seem to exist. There were no significant differences between genders but some of the parameters correlated significantly to age.

Demonstration of pelvic anatomy by modified midline transection that maintains intact internal pelvic organs.

Gross dissection for demonstrating anatomy of the human pelvis has traditionally involved one of two approaches, each with advantages and disadvantages. Classic hemisection in the median plane through the pelvic ring transects the visceral organs but maintains two symmetric pelvic halves. An alternative paramedial transection compromises one side of the bony pelvis but leaves the internal organs intact. The authors propose a modified technique that combines advantages of both classical dissections. This novel approach involves dividing the pubic symphysis and sacrum in the median plane after shifting all internal organs to one side. The hemipelvis without internal organs is immediately available for further dissection of the lower limb. The hemipelvis with intact internal organs is ideal for showing the complex spatial relationships of the pelvic organs and vessels relative to the intact pelvic floor.

Lamellar body ultrastructure revisited: high-pressure freezing and cryo-electron microscopy of vitreous sections.

Lamellar bodies are the storage sites for lung surfactant within type II alveolar epithelial cells. The structure-function models of lamellar bodies are based on microscopic analyses of chemically fixed tissue. Despite available alternative fixation methods that are less prone to artifacts, such as cryofixation by high-pressure freezing, the nature of the lung, being mostly air filled, makes it difficult to take advantage of these improved methods. In this paper, we propose a new approach and show for the first time the ultrastructure of intracellular lamellar bodies based on cryo-electron microscopy of vitreous sections in the range of nanometer resolution. Thus, unspoiled by chemical fixation, dehydration and contrasting agents, a close to native structure is revealed. Our approach uses perfluorocarbon to substitute the air in the alveoli. Lung tissue was subsequently high-pressure frozen, cryosectioned and observed in a cryo-electron microscope. The lamellar bodies clearly show a tight lamellar morphology. The periodicity of these lamellae was 7.3 nm. Lamellar bifurcations were observed in our cryosections. The technical approach described in this paper allows the examination of the native cellular ultrastructure of the surfactant system under near in vivo conditions, and therefore opens up prospectives for scrutinizing various theories of lamellar body biogenesis, exocytosis and recycling.

Sexual function after sacrocolpopexy.

INTRODUCTION: Pelvic organ prolapse affects approximately 50% of parous women over 50 years of age and has a lifetime risk of 30-50%. Vault descent or prolapse occurs in about 20% after hysterectomy and can have a negative effect on sexual function. Sacrocolpopexy is the gold standard of surgical treatment for apical prolapse in fit, sexually active patients. Few data exist which determine sexual function after sacrocolpopexy. AIM: The aim of this study was to determine sexual function in sexually active patients before and after sacrocolpopexy for the treatment of vault prolapse or descent. MAIN OUTCOME MEASURES: Main outcome measures were the International Continence Society (ICS) Pelvic Organ Prolapse (ICS POP) Staging and the Female Sexual Function Index, which were filled in before the intervention and at follow-up. METHODS: Between December 2000 and December 2009, we asked sexually active female patients who were to undergo sacrocolpopexy for vault descent or prolapse to participate in this study. The patients were gynecologically examined before and after surgery and prolapse staging was performed using the ICS POP Staging. RESULTS: Sixty-two patients were included in the study and follow-up was 24 months. The domains sexual desire, arousal, lubrication, satisfaction, and pain improved significantly postoperatively but orgasm remained unchanged. There was no vaginal shortening postoperatively, and no serious intra- or postoperative complications occurred. CONCLUSION: Sacrocolpopexy is a valuable option for sexually active patients with vault descent or prolapse with an amelioration of most aspects of sexual function but not all. Other factors as hormonal treatment, concomitant surgery, physiological, and psychological factors have to be taken into consideration.

Olfactory bulb interneurons releasing NO exhibit the Reelin receptor ApoEr2 and part of those targeted by NO express Reelin.

Nitric oxide (NO) and Reelin both modulate neuronal plasticity in developing and mature synaptic networks. We recently showed a loss of neuronal nitric oxide synthase (nNOS) protein in the olfactory bulb of reeler mutants and advanced the hypothesis that the Reelin and NO signalling pathways may influence each other. We now studied the distribution of NO sensitive guanylyl cyclase (NOsGC), Reelin and its receptor Apolipoprotein E2 (ApoEr2) in the olfactory bulb by multiple fluorescence labelling and tested whether nNOS and ApoEr2 colocalize in this area. We also essayed the protein content of NOsGC in the reeler olfactory bulb and tested whether there are any changes in nNOS and NOsGC protein in other reeler brain areas. Olfactory bulb interneurons expressing ApoEr2 and nNOS are only few in the glomerular layer but represent the large majority of granule cell layer interneurons. Conversely, NOsGC interneurons are rare in the granule cell layer and abundant as periglomerular cells. Reelin containing periglomerular cells almost entirely belong to the NOsGC subset. These data further support the hypothesis of a reciprocal signalling between Reelin/NOsGC and ApoEr2/nNOS expressing neurons to affect olfactory bulb activity. We also show that a significant rise in NOsGC content accompanies the decrease of nNOS protein in the reeler olfactory bulb. The same reciprocal changes present in the cortex/striatum and the hippocampus of reeler mice. Thus, the influence that the deficit of extracellular Reelin seems to exert on nNOS and its receptor is not limited to the olfactory bulb but is a general feature of the reeler brain.

The subcostal artery perforator flap; an anatomical study.

SUMMARY BACKGROUND: Based on a previous clinical case report in which the pedicled subcostal artery perforator flap allowed for the closure of a large defect of the lumbar region, the present study was designed to investigate the anatomy of the subcostal artery perforator flap and to evaluate its potential for wider clinical use. METHODS: A series of 14 human cadavers was studied and 28 subcostal artery perforator flaps were dissected. The location of the perforator vessel was charted against anatomical landmarks. Measurements included the perforator calibre, pedicle length, and flap size following methylene blue injection. The findings were compared by Doppler sonography in 15 volunteers. RESULTS: The subcostal artery perforator was present in all dissected specimens and in all volunteers. Its calibre measured in mean 2mm. The location was constant at the lateral border of the latissimus dorsi muscle and between 1 and 3 cm below the lower rib end. The pedicle length reached a mean of 10.5 cm when dissected up to the border of the erector spinae musculature. The vascular supply covered a mean flap size of 10 x 14 cm. The in vivo investigations confirmed the constant perforator location from the anatomical landmarks. CONCLUSION: This anatomical study reveals a considerable potential for the clinical use of the subcostal artery perforator flap for defect coverage in the lumbar area, due to its constant and reliable anatomy. Doppler sonography can be helpful in preoperative assessment of the size and the position of the subcostal perforator, thus allowing for an optimal flap design.

Nitric oxide synthase protein levels, not the mRNA, are downregulated in olfactory bulb interneurons of reeler mice.

Homozygous mutations in the Reelin gene result in severe disruption of brain development. The histogenesis of layered regions, like the neocortex, hippocampus and the cerebellum, is most notably affected in mouse reeler mutants and similar traits are also present in mice lacking molecular components of the Reelin signalling pathway. Moreover, there is evidence for an additional role of Reelin in sustaining synaptic plasticity in adult networks. Nitric oxide is an important gaseous messenger that can modulate neuronal plasticity both in developing and mature synaptic networks and has been shown to facilitate synaptic changes in the hippocampus, cerebellum and olfactory bulb. We studied the distribution and content of neuronal nitric oxide synthase in the olfactory bulbs of reeler and wildtype mice. Immunocytochemistry reveals that Reelin and neuronal nitric oxide synthase containing interneurons are two distinct, non overlapping cell populations of the olfactory bulb. We show by in situ hybridization that both nitrergic and Reelin expressing cells represent only a subset of olfactory bulb GABAergic neurons. Immunoblots show that neuronal nitric oxide synthase protein content is decreased by two thirds in reeler mice causing a detectable loss of immunolabelled cells throughout the olfactory bulb of this strain. However, neuronal nitric oxide synthase mRNA levels, essayed by quantitative real-time RT-PCR, are unaffected in the reeler olfactory bulb. Thus, disruption of the Reelin signalling pathway may modify the turnover of neuronal nitric oxide synthase in the olfactory bulb and possibly affects nitric oxide functions in reeler mice.

Reelin immunoreactivity in dissociated cultures of the postnatal hippocampus.

Reelin is an extracellular matrix glycoprotein expressed in different nerve cell populations in the developing, early postnatal and adult central nervous system. During histogenesis of the neocortex and hippocampus, reelin is present in Cajal-Retzius cells and other early neurons and contributes to correct layering of these regions. During early postnatal life, pioneer neurons disappear and reelin expression establishes in a subpopulation of cortical and hippocampal GABAergic interneurons, where it is maintained throughout adult life. We studied the developmental distribution pattern of reelin in dissociated cultures obtained from the early postnatal hippocampus to verify whether or not such a maturation phenomenon is maintained in vitro. Reelin is expressed both in Cajal-Retzius cells and multipolar and pyramidal neurons in younger cultures. The density of reelin-positive Cajal-Retzius cells dropped drastically by about 84% in 4-week-old cultures. Multipolar and pyramidal neurons containing reelin represented 12% of the total cell population in younger cultures and decreased by about 25% after 3 to 4 weeks of cultivation. Their density was significantly lower in cultures of the same age treated with glutamate receptor antagonists. These reelin-positive multipolar and pyramidal neurons were heterogeneous, including a larger amount of non-GABAergic, and 30-40% of GABAergic neurons. Cells double labeled for reelin and the GABA synthesizing enzyme glutamic acid decarboxylase represented about 4% of the total neuron population in culture and their density remained constant with age. It is thus possible that the decrease in the total reelin population may selectively be of importance to the larger non-GABAergic fraction of reelin cells. This study shows that reelin-expressing neurons are maintained in dissociated cultures of the neonatal hippocampus and their distribution and age-dependent changes in density resemble those of the early postnatal hippocampus in vivo.