Drug monitoring during ciprofloxacin prophylaxis of allogeneic stem cell transplant patients: associations with bacterial infections through a monocentric observational prospective study.

BACKGROUND: Bacterial infection ranks amongst the most common causes of morbidity and mortality in patients undergoing allogeneic haematopoietic stem cell transplantation (alloHSCT). Although ciprofloxacin (CIP) prophylaxis is recommended, information on serum levels and clinical course is lacking. AIM: To investigate relationships between CIP level and failure of prophylaxis, particularly in terms of whether different pharmacokinetic (PK) indices [area under the concentration-time curve (AUC0-24h) vs single time samples] correlate differently with the outcome. METHODS: This prospective observational monocentric study was conducted at a 1500-bed teaching hospital (March 2018-March 2019), including 63 adult patients with alloHSCT receiving CIP prophylaxis. Blood samples were drawn at three sampling times (1, 6 and 12 h post-administration), twice per week, and measured via high performance liquid chromatography. The onset of febrile episodes (FEBs) indicated suspected failure of CIP prophylaxis. Positive blood cultures [bloodstream infection (BSI)] indicated confirmed failure of prophylaxis. FINDINGS: Seven of 63 patients died without significant differences in their average CIP levels compared with survivors, with patients experiencing FEBs (54/63) displaying a 13% [95% confidence interval (CI) 4-22%] lower probability of survival. In total, 225 sets of three values (triplets) were obtained from 58 primary CIP episodes. Triplets preceding BSI with Gram-negative bacteria (GNB-BSI) showed lower AUC0-24h on average, but similar single time sample indices. An AUC0-24h of ≤21.61 mgh/L resulted in four-fold higher odds of GNB-BSI (adjusted odds ratio 3.96, 95% CI 1.21-13.00). These results were independent of the administration route, patient demographics or sampling protocol deviations, indicating reduced CIP exposure upon GNB-BSI events. CONCLUSION: Monitoring CIP levels, using multiple sampling times, may be useful to reduce alloHSCT-associated bacterial infections. Further analysis is needed to investigate causality.

Infection prevention and control between legal requirements and German Society for Hygiene and Microbiology expert assessments: a cross-sectional study in September-November 2022.

BACKGROUND: In contrast to the beginning of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), pandemic, more and more hospital issues are now regulated by policy. AIM: To identify differences between expert recommendations and legal requirements regarding infection prevention and control (IPC) strategies. METHODS: A cross-sectional study was conducted between 29th September 2022 and 3rd November 2022 addressing 1319 members of the German Society for Hygiene and Microbiology. The response rate was 12%. This paper reports the expert recommendations on different IPC strategies. FINDINGS: The majority (66%) of experts recommended universal mask usage, with 34% recommending it seasonally, even after the SARS-CoV-2 pandemic. Medical microbiology (MM) experts were more likely to recommend continuing to wear the masks indefinitely compared with IPC experts. Concerning the mask type, medical masks were recommended more frequently by IPC experts (47.3%), while FFP2 masks were preferred by MM experts (31.8%). The majority (54.7%) of experts recommended universal screening of employees, mainly in settings with extremely vulnerable patients and if regional incidence rates were high, at a frequency of twice per week. The dominant advice (recommended by at least 50% of experts) for employees exposed to SARS-CoV-2 was daily testing and wearing a mask, regardless of the length of exposure. CONCLUSIONS: Expert recommendations deviate from the legal requirements and appear to be more differentiated and proportional. The influence of specific experience and expertise on mask recommendations should be investigated in more detail. For relevant policy decisions, a quick, focused and broad-based consultation of expertise could be of added value.

Do patients need advice and information to prevent infections - results of a single centre structured survey.

Background: Healthcare-associated infections are a major burden for hospitals, leading to morbidity and mortality and unnecessary medical costs. They can probably be reduced through what is known as patient empowerment. This study aims to address the question of whether patients are interested in receiving infection prevention and control information. Methods: Patients were asked in structured interviews whether they would like more information on infection prevention and control. Inclusion criteria comprised 2 groups of patients. Group 1 were patients undergoing elective total endoprosthesis (TEP) and Group 2 were patients tested positive for meticillin-resistant Staphylococcus aureus (MRSA). Results: The response rate was 38.4 % (163/425 patients). Approximately 75 % of the patients were interested in information on infection prevention and control. The topics of interest differed between the two patient groups: MRSA patients had a higher need for infection prevention and control information. TEP patients showed a high acceptance of antiseptic body wash and a willingness to pay for it themselves. Information given to patients should be group-specific and timely. Conclusion: Our data suggest a lack of information on infection prevention and control among patients and underline the importance of patient empowerment. The willingness of patients to pay personally for antiseptic wash should be assessed further.

COVID-19 vaccination strategy for hospital staff in Germany: a cross-sectional study in March-April 2021.

BACKGROUND: SARS-CoV-2 vaccination for healthcare workers (HCWs) started in Germany in December 2020. Hospitals had little time to prepare a vaccination strategy. AIM: To gather information on the initial vaccination strategy for HCWs from the infection control practitioners in Germany. METHODS: A cross-sectional, ethically approved questionnaire was developed, formatted as an online survey and pre-tested. Infection control practitioners responsible for hygiene/infection prevention in 987 randomly selected German hospitals were invited to participate in the survey in March and April 2021. For statistical analysis, the hospitals were categorized into two groups based on bed capacity (<500 beds: small; ≥500 beds: large). FINDINGS: One hundred out of 987 (10%) infection control practitioners completed the survey. In 80% of the participating hospitals, HCW vaccination prioritization was based on recommendations of the German standing committee on vaccination (STIKO). Even so, only 54% prioritized the vaccination of HCWs with contact to vulnerable patients, thus deviating from STIKO recommendations. HCWs with a high personal health risk were prioritized for vaccination in 24% of the hospitals. Transferring unvaccinated HCWs to an area with less infection risk was considered by 2% of large and 12% of small hospitals. CONCLUSION: Vaccination prioritization differed across hospitals and deviated from STIKO recommendations. A pandemic preparedness concept should address the potential impact of divergent strategies compared to a common approach. In addition, further studies analysing the reasons why HCWs remain unvaccinated are needed to adopt effective strategies. This is especially important against the background of facility-based compulsory vaccination.

Infection control strategies for patients and accompanying persons during the COVID-19 pandemic in German hospitals: a cross-sectional study in March-April 2021.

BACKGROUND: Patients are at risk of nosocomial COVID-19 infection. The role of accompanying persons/visitors as potential infection donors is not yet well researched, but the risk will be influenced by prevention measures recommended by infection control practitioners. AIM: To collect information about COVID-19 infection control strategies for patients and accompanying persons from infection control practitioners in German hospitals. METHODS: A cross-sectional questionnaire was developed, ethically approved, pre-tested and formatted as an online tool. Infection control practitioners in 987 randomly selected German hospitals were invited to participate in March and April 2021. For statistical analysis, the hospitals were categorized as small (0-499 beds) or large (≥500 beds). FINDINGS: One hundred surveys were completed (response rate: 10%). A higher proportion of large (71%) than small (49%) hospitals let patients decide freely whether to wear medical or FFP2 masks. Most hospitals reported spatial separation for COVID-19 patients and non-COVID-19 cases (38%) or additionally for suspected COVID-19 cases (53%). A separation of healthcare teams for these areas existed in 54% of the hospitals. Accompaniment bans were more prevalent in large (52%) than in small hospitals (29%), but large hospitals granted more exemptions. CONCLUSION: The decision as to whether to separate areas and teams seemed to depend on the hospital's structural conditions, therefore impairing the implementation of recommendations. Accompaniment regulations differ between hospital sizes and may depend on patient numbers, case type/severity and patients' requirements. In the dynamic situation of a pandemic, it can be difficult to stay up to date with findings and recommendations on infection control.

Potential sources, modes of transmission and effectiveness of prevention measures against SARS-CoV-2.

During the current SARS-CoV-2 pandemic new studies are emerging daily providing novel information about sources, transmission risks and possible prevention measures. In this review, we aimed to comprehensively summarize the current evidence on possible sources for SARS-CoV-2, including evaluation of transmission risks and effectiveness of applied prevention measures. Next to symptomatic patients, asymptomatic or pre-symptomatic carriers are a possible source with respiratory secretions as the most likely cause for viral transmission. Air and inanimate surfaces may be sources; however, viral RNA has been inconsistently detected. Similarly, even though SARS-CoV-2 RNA has been detected on or in personal protective equipment (PPE), blood, urine, eyes, the gastrointestinal tract and pets, these sources are currently thought to play a negligible role for transmission. Finally, various prevention measures such as handwashing, hand disinfection, face masks, gloves, surface disinfection or physical distancing for the healthcare setting and in public are analysed for their expected protective effect.

Transmission of Staphylococcus aureus between mothers and infants in an African setting.

Staphylococcus aureus colonization is a risk factor for invasive disease. There is a need to understand S. aureus colonization in infancy as the burden of S. aureus infections in infants is high. We aimed to investigate the transmission of S. aureus between mothers and their newborns during the first year after delivery in an African setting. In a longitudinal cohort study, colonization of Gabonese mother-infant pairs was assessed at delivery and after 1, 9 and 12 months. Swabs were taken from mothers (nares, mammillae) and infants (nares and throat). Isolates were characterized and risk factors for colonization were assessed using a standardized questionnaire. We recruited 311 mothers and 318 infants including seven sets of twins. Maternal and infant colonization rates declined synchronously following a peak after 1 month at 40% (mothers) and 42% (infants). Maternal colonization was a risk factor for S. aureus carriage in infants. Based on spa typing, direct mother-to-infant transmission was evident in 5.6%. Of all methicillin-resistant isolates (n = 9), 44.4% were related to the USA300 clone; 56.7% (n = 261) of all S. aureus carried Panton-Valentine leukocidin encoding genes. Direct mother-to-infant transmission was rare and cannot explain the increase of carriage in infants within the first month. A transmission from external sources is likely and challenges the S. aureus infection control in newborns and infants in an African setting. The detection of USA300-related MRSA fuels the concern about the spread of this clone in Central Africa.

Neurobiology of secure infant attachment and attachment despite adversity: a mouse model.

Attachment to an abusive caregiver has wide phylogenetic representation, suggesting that animal models are useful in understanding the neural basis underlying this phenomenon and subsequent behavioral outcomes. We previously developed a rat model, in which we use classical conditioning to parallel learning processes evoked during secure attachment (odor-stroke, with stroke mimicking tactile stimulation from the caregiver) or attachment despite adversity (odor-shock, with shock mimicking maltreatment). Here we extend this model to mice. We conditioned infant mice (postnatal day (PN) 7-9 or 13-14) with presentations of peppermint odor and either stroking or shock. We used (14) C 2-deoxyglucose (2-DG) to assess olfactory bulb and amygdala metabolic changes following learning. PN7-9 mice learned to prefer an odor following either odor-stroke or shock conditioning, whereas odor-shock conditioning at PN13-14 resulted in aversion/fear learning. 2-DG data indicated enhanced bulbar activity in PN7-9 preference learning, whereas significant amygdala activity was present following aversion learning at PN13-14. Overall, the mouse results parallel behavioral and neural results in the rat model of attachment, and provide the foundation for the use of transgenic and knockout models to assess the impact of both genetic (biological vulnerabilities) and environmental factors (abusive) on attachment-related behaviors and behavioral development.

Histone acetylation in the olfactory bulb of young rats facilitates aversive olfactory learning and synaptic plasticity.

Epigenetic mechanisms play an important role in memory formation and synaptic plasticity. Specifically, histone-associated heterochromatin undergoes changes in structure during the early stages of long-term memory formation. In keeping with the classical conditioning paradigm, young rats have been shown to exhibit aversion to an odor stimulus initially presented during foot shock. We previously showed that synaptic plasticity at the dendrodendritic synapses between mitral and granule cells in the olfactory bulb (OB) underlies this aversive olfactory learning. However, the epigenetic mechanisms involved are not well characterized. Therefore, we examined whether intrabulbar infusion of trichostatin A (TSA), a histone deacetylase inhibitor, facilitates olfactory learning in young rats. TSA infusion during odor-shock training enhanced a conditioned odor aversion in a dose-dependent manner and prolonged the learned aversion. Western blot and immunohistochemical analyses showed that the level of histone H4 acetylation significantly increased until 4 h after odor-shock training in both mitral and granule cells in the OB, whereas histone H3 acetylation returned to the control level at 2 h after the training. We also obtained evidence that TSA infusion elevated acetylation of histone H4 or H3. Furthermore, in vitro electrophysiological analysis using slices of the OB revealed that application of TSA significantly enhanced the long-term potentiation induced in synaptic transmission from mitral to granule cells at dendrodendritic synapses. Taken together, these results provide evidence that histone H4 and H3 acetylation in the OB is an epigenetic mechanism associated with aversive olfactory learning in young rats.

[Causes and characteristics of patient death under ARV at the Dermatology-Venereology Department of the Donka National Hospital, GUINEA]. / Causes et caracteristiques des deces des patients sous ARV au service Dermatologie-Venereologie de L'Hopital National Donka, Guinee.

INTRODUCTION: The antiretroviral treatments led to a spectacular reduction of morbidity and mortality of HIV-infected patients, transforming it into a chronic infection. HIV infection remains potentially lethal and requires a long term treatment to obtain an immunological and virological control. The goal of this work was to describe the characteristics of the deaths during the ARV treatment. MATERIALS AND METHOD: We led a descriptive retrospective study of a 4 year period, from July 2004 to August 2007 which looked at 429 patient under ARV followed in the dermatology - venereology department of the Donka national hospital and whose death during hospitalization occurred for the study period. We excluded the patients who suffered loss of sight or who died during the ARV treatment period. RESULTS: On 429 included patients, recorded death rate was of 27,7%. The mean age of included patients was 42 ± 6.5 years old. Patients at the stage 3 and 4 of the WHO classification recorded the greatest number of death. There was no patient at stage I. More half of the patients were immunosuppressed with a count of CD4 < 200/mm3. In our study 66 patients died with a rate of CD4 < 200/mm3 21 patients with a rate of CD4 ranging between 200 and 499 or 17,6%. Only one patient had a rate of CD4 > 500/mm3 while 31 other patients did not have a CD4 at the time of the death. We recorded 57 deaths in the first 6 months of HAART (among which 32 occurred within the first 3 months) and 24 after. The leading causes of death were tuberculosis (47,05%) including 64,28% of pulmonary localization and 35,71% of extrapulmonary localization, followed by cerebral toxoplasmosis (19,62%) and Kaposi disease (15,12%). The other causes of death found were hepatitis B (4,20%) and neuro-meningeal cryptococcosis (2,52%). A socio-economic unstable situation was found at half of the patients For 14 case the cause of death remained unknown. There no was death due to side effects of the ARV therapy. 89,1% of the patients deceased were under protocol 2 INTI + 1 INNTI which represents the layout of first line in our country. CONCLUSION: The mortality of the infection by HIV remains high in spite of the introduction of ARV treatment into our service. The patients who passed away were mainly characterized by a low level of CD4 and a very advanced stage of the evolution of the infection to the initiation of the ARV. The leading causes of death were opportunist infections. An early tracking of the infection by HIV and an early and optimal assumption of responsibility of the opportunist infections could contribute to reverse the tendencies in Guinea.

Les traitements antirétroviraux (ARV) ont permis d'obtenir une réduction spectaculaire mais non complète de la morbidité et de la mortalité à VIH. Cependant malgré ces résultats positifs, plusieurs études rapportent des taux de mortalité élevée chez des patients soumis aux traitements ARV. Le but de ce travail était de décrire les caractéristiques des décès au cours du traitement ARV. MATÉRIEL ET MÉTHODE: Il s'agissait d'une étude rétrospective descriptive d'une période de 4 ans, allant de juillet 2004 à août 2007 portant sur 429 patients sous traitement ARV suivis dans le service de dermatologie-vénéréologie de l'hôpital national guinéen de Donka et dont le décès est survenu dans le service pendant la période d'étude. RESULTATS: Sur 429 patients sous ARV inclus dans l'étude, 119 étaient décédés soit une fréquence de 27,7%. L'âge moyen de nos patients était de 42 ± 6,5 ans. Il y avait une légère prédominance féminine (52,1%) avec un sex ratio F/H égal à 1,08. Les patients au stade 3 et 4 de la classification de l'OMS ont enregistré le plus grand nombre de décès. Aucun patient n'était au stade I. Plus de moitié des patients étaient dans un état de déficit immunitaire très profond (CD4 < 200 / mm3). Au cours de notre étude, 66 patients étaient décédés avec un taux de CD4 < 200 / mm3 soit 55%. Nous avons enregistré 57 décès (47,9%) dans les 6 mois suivants l'introduction du traitement anti VIH dont 32 (soit 26,9% de l'ensemble des décès enregistrés) dans les 3 premiers mois alors que 24 patients (20,2%) étaient décédés après 6 mois de traitement. Les principales causes de décès étaient la tuberculose (47,05%), dont 64,28% de localisation pulmonaire, suivie de la toxoplasmose cérébrale (19,62%) et la maladie de Kaposi (15,12%). Les autres causes de décès retrouvées étaient l'hépatite B (4,20%) et la cryptococcose neuro-méningée (2,52%). Pour 14 cas soit 11,76% la cause de décès était inconnue. Aucun décès dû aux effets secondaires des ARV n'était noté. La majorité (89,1%) des patients décédés étaient sous le protocole 2 INTI + 1 INNTI qui représente le schéma de première ligne dans notre pays. CONCLUSION: La mortalité de l'infection par le VIH reste élevée malgré l'introduction du traitement ARV dans notre service. Les patients décédés étaient principalement caractérisés par un faible taux de CD4 et un stade très avancé de l'évolution de l'infection à l'initiation des ARV. Les principales causes de décès étaient les infections opportunistes. Un dépistage précoce de l'infection par le VIH et une prise en charge précoce et optimale des infections opportunistes pourraient contribuer à inverser les tendances en Guinée.

Common properties between synaptic plasticity in the main olfactory bulb and olfactory learning in young rats.

Aversive olfactory learning was established in young rats after odor exposure paired with foot shock through a classical conditioning paradigm. Using behavioral pharmacology and Western blotting, we previously reported that plasticity in the main olfactory bulb (MOB) underlies aversive olfactory learning. Since long-term potentiation (LTP) observed in the hippocampus is believed to be a cellular substrate for aspects of memory, we attempted to induce LTP in the MOB. Using brain slices containing the MOB, we found that five tetani of the lateral olfactory tract evoked LTP that was blocked by the N-methyl-d-aspartate (NMDA) receptor antagonist AP5. Although three tetani induced no significant changes in control slices, with noradrenaline (NA) application they produced clear LTP (NA-mediated LTP), which was not dependent on NMDA receptors. NA's facilitating effect on LTP induction was blocked by the beta-adrenoceptor antagonist timolol but not by the alpha-adrenoceptor antagonist phentolamine, and was mimicked by the beta-adrenoceptor agonist isoproterenol. The l-type calcium channel blocker nifedipine completely blocked LTP as well as NA-mediated LTP. In addition, we found that aversive olfactory learning was impaired by beta-adrenoceptor antagonist, timolol but not by alpha-adrenoceptor antagonist, phentolamine, and only odor training established olfactory learning by isoproterenol infusion. Moreover, we found that nifedipine but not AP5 prevented olfactory learning formation. These common properties provided evidence for neural correlates between NA-mediated LTP aversive olfactory learning in young rats.

Functional synapse formation between cultured rat accessory olfactory bulb neurons and vomeronasal pockets.

To investigate the interaction between vomeronasal receptor neurons and accessory olfactory bulb neurons during pheromonal signal processing and specific synapse formation, partially dissociated rat vomeronasal receptor neurons were co-cultured with accessory olfactory bulb neurons. Between 7 and 14 days in co-culture, a few bundles of fibers from a spherical structure, termed the vomeronasal pocket, of cultured vomeronasal receptor neurons extended to the accessory olfactory bulb neurons. An optical recording of the intracellular Ca(2+) concentration was used to monitor the synaptic activation of cultured accessory olfactory bulb neurons. Electrical stimulation of the vomeronasal pocket between 7 and 14 days in co-culture had no effects on most of the cultured neurons tested, although it occasionally evoked weak responses in a small number of neurons. In contrast, vomeronasal pocket stimulation after 21 days in co-culture evoked clear calcium transients in a substantial number of cultured accessory olfactory bulb neurons. These responses of accessory olfactory bulb neurons were reversibly suppressed by the application of 6-cyano-7-nitroquinoxaline-2,3-dione; the calcium transients disappeared in most of the neurons and were diminished in the others. The application of d-2-amino-5-phosphonopentanoic acid partially affected the calcium transients, but blocked spontaneous calcium increases, which were observed repeatedly in accessory olfactory bulb-alone cultures. The application of both 6-cyano-7-nitroquinoxaline-2,3-dione and d-2-amino-5-phosphonopentanoic acid completely blocked the evoked calcium transients. These results suggest that functional glutamatergic synapses between vomeronasal receptor neurons and accessory olfactory bulb neurons were formed at around 21 days in co-culture.

Activation of the mitogen-activated protein kinase/extracellular signal-regulated kinase signaling pathway leading to cyclic AMP response element-binding protein phosphorylation is required for the long-term facilitation process of aversive olfactory learning in young rats.

The mitogen-activated protein kinase/extracellular-signal regulated kinase (MAPK/ERK) cascade is an important contributor to synaptic plasticity that underlies learning and memory. ERK activation by the MAPK/ERK kinase (MEK) leading to cyclic-AMP response element binding protein (CREB) phosphorylation is implicated in the formation of long-term memory. We have demonstrated that CREB phosphorylation in the olfactory bulb (OB) is important for aversive olfactory learning in young rats, yet whether MAPK/ERK functions as an upstream regulator are necessary for this olfactory learning remains to be determined. Therefore, we addressed this issue using behavioral and Western blot analyses. The MEK inhibitor PD98059 was continuously infused into the OB of postnatal day 11 rat pups during a 30-min training session regarding the pairing of citral odor and foot shock. On the following day, the time spent in the part of the apparatus where the odor was present was measured as an index of odor aversion. PD98059 impaired olfactory learning in a dose-dependent manner without affecting memory retention 1 h after training. We further tested whether odor-shock training leads to MAPK/ERK activation in the OB and defines the time course of the activation. Phosphorylated ERKs (P-ERKs) 1 and 2 were significantly increased for 60 min after the training without changes in total ERKs 1 and 2. By contrast, intrabulbar infusion of PD98059 during the training significantly reduced P-ERKs 1 and 2 as well as phosphorylated CREB without any effects on the total ERKs or CREB. Taken together with the previous findings, these results indicate that the MAPK/ERK-CREB pathway is required for the long-term, but not the short-term, facilitation process of aversive olfactory learning in young rats.

Activation of the cyclic AMP response element-binding protein signaling pathway in the olfactory bulb is required for the acquisition of olfactory aversive learning in young rats.

Long-term memory formation requires both gene expression and protein synthesis. Phosphorylation of the transcription factor cyclic AMP response element-binding protein (CREB) is thought to be important in processes underlying long-term memory. To clarify the role of CREB in olfactory aversive learning in young rats, we carried out behavioral pharmacology and Western blot analyses. On postnatal day 11, oligodeoxynucleotides were infused directly into the bilateral olfactory bulbs through cannulae implanted prior to training in a classical conditioning paradigm with citral odor and foot shock. On the following day the odor preference test was performed. After training, saline-infused animals spent significantly shorter time over the citral odor zone. Infusion of CREB antisense oligodeoxynucleotides 6 h before or during training, however, prevented olfactory aversive learning without affecting memory retention 1 h after training. CREB scrambled oligodeoxynucleotides infusions had no effect on olfactory learning. When infused 6 h after training, none of oligodeoxynucleotides had an effect on time spent over the odor zone. Using Western blotting, we analyzed CREB in nuclear extracts obtained from the young rats after training. Marked increases in phosphorylated CREB were sustained from 10 to 360 min after the odor-shock pairing in animals which were subjected to both, in comparison with levels 30 min in animals which were subjected to odor only or no stimulation. Total CREB levels showed no differences among groups. Infusion of CREB antisense oligodeoxynucleotides significantly reduced the expression of phosphorylated and total CREBs in the olfactory bulb. These results show that the synthesis and phosphorylation of CREB are required for the acquisition of olfactory aversive learning in young rats, and that this requirement for the CREB signaling pathway has a critical time window.

Non-specific olfactory aversion induced by intrabulbar infusion of the GABA(A) receptor antagonist bicuculline in young rats.

On postnatal day 12, young rats show an aversion to an odor to which they had been exposed along with presentations of foot shock on postnatal day 11. The acquisition of this aversive learning involves and requires disinhibition of the mitral/tufted cells induced by centrifugal noradrenergic activation during somatosensory stimulation. This olfactory learning is established only for the odor to which the rat has been exposed during conditioning. Infusion of the GABA(A) receptor antagonist bicuculline at a high dose (2.0 nmol/each olfactory bulb) into the olfactory bulb in the presence of an odor is capable of developing olfactory aversive responses without somatosensory stimulation in young rats. The purpose of this study is to characterize the properties of bicuculline-induced aversive responses. In contrast to the odor specificity of aversive learning produced by odor-shock conditioning, bicuculline-induced aversive responses lack odor specificity. Namely, bicuculline infusion in the presence of a citral odor results, in a dose-dependent manner, in subsequent aversive responses to strange odors (benzaldehyde and vanillin) that have never been presented. Moreover, bicuculline infusion alone is sufficient to produce dose-dependent aversive responses to strange odors (citral, benzaldehyde and geraniol). From these results we suggest that disinhibition of mitral/tufted cells from granule cells by bicuculline infusion makes young rats aversive to strange odors non-specifically, as if the rats had learned the odor aversion as a result of odor exposure paired with foot shock. Different mechanisms of disinhibition of the mitral/tufted cells may underlie both the pharmacological manipulation and noradrenergic activation by somatosensory stimulation.

Properties of reciprocal synapses in the mouse accessory olfactory bulb.

Reciprocal dendrodendritic synapses between mitral and granule cells in the accessory olfactory bulb have been implicated in a specialized form of olfactory learning in mice, in which a female forms a memory to the pheromonal signal of the male that mates with her. Relatively little is known, however, about the mechanism of synaptic transmission at the reciprocal synapses. We analyzed synaptic currents generated in accessory olfactory bulb mitral cells in slice preparations with the patch-clamp technique in nystatin-perforated whole-cell configuration. A brief (5-20-ms) depolarizing voltage step from -70 to 0 mV applied to a single mitral cell evoked GABA(A) receptor-mediated inhibitory postsynaptic currents. The inhibitory postsynaptic currents persisted in the presence of tetrodotoxin, indicating that the inhibitory postsynaptic current in mitral cells can be elicited through purely dendritic interactions. The inhibitory postsynaptic currents were greatly enhanced by washout of extracellular Mg(2+). In Mg(2+)-free solution, the N-methyl-D-aspartate (NMDA) receptor antagonist D,L-2-amino-5-phosphonovaleric acid greatly reduced the inhibitory postsynaptic currents, whereas the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-(1H,4H)-dione (CNQX) slightly reduced them. These data demonstrate that NMDA receptors play an important role in the generation of dendrodendritic inhibition in mitral cells of the mouse accessory olfactory bulb.

Stimulus-dependence of NO-mediated neuronal activation: a Fos expression study in the hippocampus and cortex of lactating rats.

We investigated how simultaneous manipulation of suckling and i.c.v. injection of nitric oxide (NO)-related pharmacological agents affect Fos activation in the hippocampus and cortex of lactating rats. Dams received drugs or vehicle injection just prior to reunion with their pups following a 12 h separation and Fos protein activation was examined after 2 h of suckling. In conscious dams, sodium nitroprusside (SNP, an NO donor) significantly activated Fos expression in the hippocampus and cortex compared with vehicle or an NO synthase inhibitor. Urethane anaesthesia abolished Fos expression in the cortex, but not in the hippocampus following simultaneous SNP injection and resumption of suckling. Fos activation in the hippocampus and cortex was significantly attenuated when SNP was injected alone (without dam-pups reunion after separation). Coincident injection of SNP with a NO synthase inhibitor abolished all Fos activation in the hippocampus and cortex. In chronically lactating rats (without any interruption of suckling) SNP injection failed to activate any Fos expression. These observations underscore the importance of stimulus modality in revealing the dynamics of NO-mediated neuronal function within a discrete tissue entity such as the hippocampus or the cortex, which may be relevant to other regions of the brain.

Activation of GABA(A) receptors in the accessory olfactory bulb does not prevent the formation of an olfactory memory in mice.

When female mice are mated, they form a memory to the pheromonal signal of their male partner. The neural mechanisms underlying this memory involve changes at the reciprocal dendrodendritic synapses between glutamatergic mitral cells and gamma-aminobutyric acid (GABA)-ergic granule cells in the accessory olfactory bulb (AOB). Blockade of GABA(A) receptors in the AOB leads to the formation of an olfactory memory. In an attempt to disrupt memory formation at mating, we used local infusions of the GABA(A) receptor agonist muscimol into the AOB during the critical period for memory formation. Muscimol across a wide range of doses (1-1000 pmol) did not prevent memory formation. The resistance of this memory to GABA(A) receptor activation may reflect the complexity of synaptic microcircuits in the AOB.

Modulation of dendrodendritic interactions and mitral cell excitability in the mouse accessory olfactory bulb by vaginocervical stimulation.

When female mice are mated, they form a memory to the pheromonal signal of their male partner. The neural changes underlying this memory occur in the accessory olfactory bulb, depend upon vaginocervical stimulation at mating and involve changes at the reciprocal synapses between mitral and granule cells. However, the action of vaginocervical stimulation on the reciprocal interactions between mitral and granule cells remains to be elucidated. We have examined the effects of vaginocervical stimulation on paired-pulse depression of amygdala-evoked field potentials recorded in the external plexiform layer of the accessory olfactory bulb (AOB) and the single-unit activity of mitral cells antidromically stimulated from the amygdala in urethane-anaesthetized female mice. Artificial vaginocervical stimulation reduced paired-pulse depression (considered to be due to feedback inhibition of the mitral cell dendrites from the granule cells via reciprocal dendrodendritic synapses) recorded in the AOB external plexiform layer. As would be expected from this result, vaginocervical stimulation also enhanced the spontaneous activity of a proportion of the mitral cells tested. These results suggest that vaginocervical stimulation reduces dendrodendritic feedback inhibition to mitral cells and enhances their activity.

Oxytocin enhances presynaptic and postsynaptic glutamatergic transmission between rat olfactory bulb neurones in culture.

Although oxytocin (OT) within the olfactory bulb has been implicated in maternal behaviour and olfactory recognition, the cellular mechanisms of action remain to be clarified. We examined the effects of OT on glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs) in cultured granule cells with the use of whole-cell patch-clamp recordings. OT reversibly increased both the frequency and amplitude of sEPSCs. The effects of OT on sEPSCs were blocked by the selective OT receptor antagonist desGly-NH(2)(9),d (CH(2))(5)-[Thy(Me)(2),Thr(4)]-ornithine vasotocin. OT had no detectable effect, however, on high voltage-activated Ca2+ currents in mitral/tufted cells, suggesting that OT acts presynaptically on step(s) in the release process downstream from calcium influx. OT augmented the membrane current in granule cells evoked by exogenous application of glutamate, indicating a postsynaptic site of action. These results indicate that OT facilitates sEPSCs in granule cells by both pre- and postsynaptic mechanisms.