Polygenic contributions to performance on the Balloon Analogue Risk Task.

Risky decision-making is a common, heritable endophenotype seen across many psychiatric disorders. Its underlying genetic architecture is incompletely explored. We examined behavior in the Balloon Analogue Risk Task (BART), which tests risky decision-making, in two independent samples of European ancestry. One sample (n = 1138) comprised healthy participants and some psychiatric patients (53 schizophrenia, 42 bipolar disorder, 47 ADHD); the other (n = 911) excluded for recent treatment of various psychiatric disorders but not ADHD. Participants provided DNA and performed the BART, indexed by mean adjusted pumps. We constructed a polygenic risk score (PRS) for discovery in each dataset and tested it in the other as replication. Subsequently, a genome-wide MEGA-analysis, combining both samples, tested genetic correlation with risk-taking self-report in the UK Biobank sample and psychiatric phenotypes characterized by risk-taking (ADHD, Bipolar Disorder, Alcohol Use Disorder, prior cannabis use) in the Psychiatric Genomics Consortium. The PRS for BART performance in one dataset predicted task performance in the replication sample (r = 0.13, p = 0.000012, pFDR = 0.000052), as did the reciprocal analysis (r = 0.09, p = 0.0083, pFDR=0.04). Excluding participants with psychiatric diagnoses produced similar results. The MEGA-GWAS identified a single SNP (rs12023073; p = 3.24 × 10-8) near IGSF21, a protein involved in inhibitory brain synapses; replication samples are needed to validate this result. A PRS for self-reported cannabis use (p = 0.00047, pFDR = 0.0053), but not self-reported risk-taking or psychiatric disorder status, predicted behavior on the BART in our MEGA-GWAS sample. The findings reveal polygenic architecture of risky decision-making as measured by the BART and highlight its overlap with cannabis use.

Natural organic matter fractions and their removal in full-scale drinking water treatment under cold climate conditions in Nordic capitals.

Drinking water treatment plants (DWTPs) designed to remove natural organic matter (NOM) are challenged as concentrations of NOM in raw waters are increasing. Here, we assess seasonal differences in NOM quality and quantity, from raw waters to the distribution network, at three large DWTPs in Oslo, Stockholm and Helsinki. Samples, collected during stable stratification in both winter and summer and during the autumnal turnover, were analysed for NOM concentrations and composition. The NOM was characterized by common routine parameters, size and content (TFF, LC-OCD, fluorescence) and biodegradability. The NOM concentration decreased to 2.5 mg/L (55%), 4.0 mg/L (48%) and 5.7 mg/L (76%) at the respective DWTPs in Oslo, Stockholm and Helsinki. The NOM in raw waters were predominantly in the largest size fraction (>50 kDa), in particular from Oslo. High MW fractions >50 kDa and humics remained the largest fractions with minimum 30% and maximum 80% of the total NOM. The BDOC in treated water <0.3 mg/L and the conditions in the distribution network imply low probability for bacteria regrowth. The multi-step treatment consisting of coagulation/flocculation, sedimentation, rapid sand filtration, ozonation and biological activated carbon filtration (BAC) was most effective in removing NOM. Coagulation/flocculation followed by sedimentation and sand filtration were critical, especially for the removal of biopolymers and humics, and somewhat for building blocks. The sand filtration provided up to 25% additional removal of biopolymers and below 7% removal of other fractions. The ozonation and BAC was more effective and removed 11% of biopolymers, and about 35% of building blocks and LMW neutrals.

The use of an electronic clinical rule to discontinue chronically used benzodiazepines and related Z drugs.

PURPOSE: The chronic use of benzodiazepines and benzodiazepine-related drugs (BZ/Z) in older people is common and not without risks. The objective of this study was to evaluate whether the implementation of a clinical rule promotes the discontinuation of chronically used BZ/Z for insomnia. METHODS: A clinical rule, generating an alert in case of chronic BZ/Z use, was created and applied to the nursing home (NH) setting. The clinical rule was a one-off intervention, and alerts did not occur over time. Reports of the generated alerts were digitally sent to NH physicians with the advice to phase out and eventually stop the BZ/Z. In cases where the advice was adopted, a follow-up period of 4 months on the use of BZ/Z was taken into account in order to determine whether the clinical rule alert led to a successful discontinuation of BZ/Z. RESULTS: In all, 808 NH patients were screened. In 161 (19.1%) of the patients, BZ/Z use resulted in a clinical rule alert. From these, the advice to phase out and stop the BZ/Z was adopted for 27 patients (16.8%). Reasons for not following the advice consisted of an unsuccessful attempt in the past (38 patients), patients family and/or patient resistance (37 patients), the non-continuous use of BZ/Z (32 patients) and indication still present (27 patients). Of the 12 NH physicians, seven adopted the advice. CONCLUSIONS: The success rate of a clinical rule for discontinuation of chronically used BZ/Z for insomnia was low, as reported in the present study. Actions should be taken to help caregivers, patients and family members understand the importance of limiting BZ/Z use to achieve higher discontinuation rates.

Immune dysregulation in offspring of a bipolar parent. Altered serum levels of immune growth factors at adolescent age.

Immune dysregulation plays a role in the vulnerability for mood disorders. Immune growth factors, such as Stem Cell Factor (SCF), Insulin-like Growth Factor-Binding Protein-2 (IGF-BP2), Epidermal Growth Factor (EGF), IL-7 and sCD25 have repeatedly been reported altered in patients with mood disorders. The aim of this study was to investigate levels of these factors in serum of adolescent bipolar offspring, who have a heightened risk for mood disorder development and to also analyze the data combined with previously published data. Growth factors were assessed by CBA/ELISA in adolescent bipolar offspring (n=96, mean age=16years) and in age- and gender-matched healthy controls (n=50). EGF belonged to a mutually correlating cluster of mainly neurotrophic compounds including S100B and BDNF, which were in general decreased in serum. IL-7, SCF, IGF-BP2 and sCD25, belonged to a different mutually correlating cluster of immune growth factors, which were in general increased: IGF-BP2 significantly in serum of offspring without a mood disorder, IL-7 and SCF in serum of offspring who had experienced a mood episode. This pattern of de- and increases was not different between bipolar offspring that developed or did not develop a mood disorder over time, apart from the IGF-BP2 level, which was near significantly higher in offspring later developing a mood disorder. Correlations with the previously published immune-cellular abnormalities were not found. In conclusion non-affected adolescents at familial mood disorder development risk were characterized by a distinct pattern of a series of compounds operating in a network of hematopoiesis, neurogenesis and inflammation.

Durable efficacy of liraglutide in patients with type 2 diabetes and pronounced insulin-associated weight gain: 52-week results from the Effect of Liraglutide on insulin-associated wEight GAiN in patients with Type 2 diabetes' (ELEGANT) randomized controlled trial.

BACKGROUND: Pronounced weight gain frequently complicates insulin therapy in patients with type 2 diabetes (T2DM). We have previously reported that addition of liraglutide for 26 weeks can reverse insulin-associated weight gain, decrease insulin dose and improve glycaemic control, as compared with continuation of standard insulin treatment. OBJECTIVES: To investigate whether the beneficial effects of liraglutide are sustained up to 52 weeks and whether similar effects could be obtained when liraglutide is added 6 months later. METHODS: Adult T2DM patients with ≥ 4% weight gain within 16 months of insulin therapy completing the first 26-week trial period of open-label addition of liraglutide 1.8 mg day(-1) (n = 26) versus continuation of standard insulin therapy (n = 24) were all treated with liraglutide for another 26 weeks. Results were analysed according to the intention-to-treat principle. RESULTS: Overall, 24 (92%) and 18 (75%) patients originally assigned to liraglutide and standard therapy, respectively, completed the study. Addition of liraglutide decreased body weight to a similar extend when given in the first 26 weeks (liraglutide group) or second 26 weeks (original standard therapy group): -4.4 vs. -4.3 kg (difference -0.32 kg, 95% confidence interval -2.2 to 1.6 kg; P = 0.74). Similar results were also seen in the two groups with regard to decrease in haemoglobin A1c (HbA1c ) (-0.77 vs. -0.66%; P = 0.23) and insulin dose (-28 vs. -26 U day(-1) ; P = 0.32). In both groups, 22% of patients could discontinue insulin. Continuation of liraglutide until 52 weeks led to sustained effects on body weight, HbA1c and insulin-dose requirements. CONCLUSION: In T2DM patients with pronounced insulin-associated weight gain, addition of liraglutide within 2 years leads to sustained reversal of body weight, improved glycaemic control and decrease in insulin dose. Thus, liraglutide offers a valuable therapeutic option.

A dynamic course of T cell defects in individuals at risk for mood disorders.

OBJECTIVES: T cell abnormalities have been repeatedly reported in adult patients with mood disorders, suggesting a role of these cells in the pathogenesis of these disorders. In the present study, we explored the dynamics of circulating T cell subsets over time in a population at high familial risk for developing a mood disorder. METHODS: Children of a parent with bipolar disorder (bipolar offspring, N=140) were assessed at three time-points: adolescence, young adulthood and adulthood. We carried out a detailed fluorescence-activated cell sorting (FACS) analysis to determine various T cell subsets from frozen stored peripheral blood mononuclear cells of bipolar offspring and age- and gender-matched healthy controls at each time-point. RESULTS: Throughout the period of observation reduced levels of CD3+ and CD3+ CD4+ T cells were observed. In bipolar offspring Th1, Th2, Th17 and natural T regulatory cells (Tregs) followed a dynamic course over time with reduced levels of Tregs in adolescence and a reduced relative number of Th1, Th17 cells in young adulthood. In post hoc analysis Tregs were inversely associated with the pro-inflammatory monocyte state determined previously (rs=-0.220, p=0.001). Significant associations between T cell subset abnormalities and psychopathology such as mood disorders were not found. CONCLUSIONS: A subtle partial T cell defect was present in bipolar offspring from adolescence through adulthood. Within this defect the dynamic change of inflammatory and regulatory T cell subsets suggests a high inflammatory state during adolescence, a reduced inflammatory state during young adulthood and a virtually normalized state at adulthood.

Insulin administered by needle-free jet injection corrects marked hyperglycaemia faster in overweight or obese patients with diabetes.

AIMS: To test whether jet injection of insulin resulted in faster correction of marked hyperglycaemia than when insulin is injected by a conventional pen in patients with diabetes. METHODS: Adult, overweight or obese (BMI ≥25 and ≤40 kg/m(2)) patients with type 1 diabetes (n = 10) or insulin-treated type 2 diabetes (n = 10) were enrolled in a randomized, controlled, crossover study. On two separate occasions, patients were instructed to reduce insulin dose(s) to achieve marked hyperglycaemia (18-23 mmol/l). Subsequently, insulin aspart was administered either by jet injection or by conventional pen, in a dose based on estimated individual insulin sensitivity. Pharmacodynamic and pharmacokinetic profiles were derived from plasma glucose and insulin levels, measured for 6 h after injection. RESULTS: After conventional injection, plasma glucose concentration dropped by ≥10 mmol/l after 192.5 ± 13.6 min. The jet injector advanced this time to 147.9 ± 14.4 min [difference 44.6 (95% confidence interval 4.3, 84.8); P = 0.03], except in 3 patients who failed to reach this endpoint. The time advantage exceeded 1.5 h in patients with a BMI above the median. Jet injection also reduced the hyperglycaemic burden during the first 2 h (2042 ± 37.2 vs 2168 ± 26.1 mmol/min; P = 0.01) and the time to peak insulin levels (40.5 ± 3.2 vs 76.8 ± 7.7 min; P < 0.001), but did not increase the risk for hypoglycaemia. CONCLUSIONS: Administration of rapid-acting insulin by jet injection results in faster correction of marked hyperglycaemia in overweight or obese patients with insulin-requiring diabetes.

Does acute stress play a role in the lasting therapeutic effects of psychedelic drugs?

Psychedelic drugs, when used in the context of psychotherapy, can produce significant and long-lasting memories with enduring beneficial effects. Yet, the behavioral and neurobiological mechanisms that underlie these beneficial effects remain a mystery. Here, we suggest that both the quality and durability of memories of the drug-facilitated therapeutic experience may be mediated, in part, by the acute stress responses induced by the drugs. It is known that high doses of psychedelic drugs activate autonomic and hormonal stress responses. For evolutionarily adaptive reasons, acute stress is known to i) instill meaning to the immediate context in which it is experienced, and ii) lead to the formation of salient and lasting memories of the events surrounding the stress. Thus, the stress-inducing effect of psychedelic drugs may contribute to the reported sense of meaning, as well as the durability of the memory of the drug experience. When used in a therapeutic context these actions may i) enhance the salience of insights gained during the experience and ii) strengthen the memories formed by these experiences. Future empirical studies will help to determine whether acute stress contributes to the emotional significance and lasting effects of psychedelic-assisted psychotherapy.

Asymmetric vestibular evoked myogenic potentials in unilateral Menière patients.

Vestibular evoked myogenic potentials (VEMPs) were measured in 22 unilateral Menière patients with monaural and binaural stimulation with 250 and 500 Hz tone bursts. For all measurement situations significantly lower VEMP amplitudes were on average measured at the affected side compared to the unaffected side. Unilateral Menière patients have, in contrast to normal subjects, asymmetric VEMPs, indicating a permanently affected vestibular (most likely otolith) system at the side of hearing loss. The diagnostic value of VEMP amplitude asymmetry measurement in individual patients is low, because of the large overlap of the VEMP amplitude asymmetry range for unilateral Menière patients with that for normal subjects.

An artificial intelligence deep learning model for identification of small bowel obstruction on plain abdominal radiographs.

OBJECTIVES: Small bowel obstruction is a common surgical emergency which can lead to bowel necrosis, perforation and death. Plain abdominal X-rays are frequently used as a first-line test but the availability of immediate expert radiological review is variable. The aim was to investigate the feasibility of using a deep learning model for automated identification of small bowel obstruction. METHODS: A total of 990 plain abdominal radiographs were collected, 445 with normal findings and 445 demonstrating small bowel obstruction. The images were labelled using the radiology reports, subsequent CT scans, surgical operation notes and enhanced radiological review. The data were used to develop a predictive model comprising an ensemble of five convolutional neural networks trained using transfer learning. RESULTS: The performance of the model was excellent with an area under the receiver operator curve (AUC) of 0.961, corresponding to sensitivity and specificity of 91 and 93% respectively. CONCLUSION: Deep learning can be used to identify small bowel obstruction on plain radiographs with a high degree of accuracy. A system such as this could be used to alert clinicians to the presence of urgent findings with the potential for expedited clinical review and improved patient outcomes. ADVANCES IN KNOWLEDGE: This paper describes a novel labelling method using composite clinical follow-up and demonstrates that ensemble models can be used effectively in medical imaging tasks. It also provides evidence that deep learning methods can be used to identify small bowel obstruction with high accuracy.

The effect of changes in perilymphatic K+ on the vestibular evoked potential in the guinea pig.

To investigate the effect on the functioning of the vestibular system of a rupture of Reissner's membrane, artificial endolymph was injected in scala media of ten guinea pigs and vestibular evoked potentials (VsEPs), evoked by vertical acceleration pulses, were measured. Directly after injection of a sufficient volume to cause rupture, all ears showed a complete disappearance of VsEP, followed by partial recovery. To investigate the effect of perilymphatic potassium concentration on the vestibular sensory and neural structures, different concentrations of KCl were injected directly into the vestibule. The KCl injections resulted in a dose-dependent decrease of VsEP, followed by a dose-dependent slow recovery. This animal model clearly shows a disturbing effect of a higher than normal K(+) concentration in perilymph on the vestibular and neural structures in the inner ear. Potassium intoxication is the most probable explanation for the observed effects. It is one of the explanations for Menière attacks.

[Medication and comedication in COVID-19 patients]. / Geneesmiddelen bij COVID-19.

This paper discusses the possible effects of comedication on COVID-19 and the current treatment options for this infection. It is very doubtful that comedication has a disadvantageous effect on the course of the disease. NSAIDs should be avoided in any patient with a possible severe disease, because of potential side effects. Inhibitors of the renin-angiotensin aldosterone system should be continued when there is a solid indication, and stopped in case of hemodynamic problems. There is no preference for either ACE inhibitors or angiotensin II receptor inhibitors. Currently, chloroquine and remdesivir are possible treatment options. There is no sound evidence for either treatment. Chloroquine has side effects (nausea, QT prolongation) and there are several drug interactions. The treatment should be reconsidered in the event of side effects and when inferior medication for comorbidity must be prescribed because of possible interactions. Lopinavir/ritonavir is not effective. Supportive care is at present the mainstay of the treatment.

Three-dimensional reconstruction of the guinea pig inner ear, comparison of OPFOS and light microscopy, applications of 3D reconstruction.

Three-dimensional (3D) reconstruction of anatomical structures can give additional insight into the morphology and function of these structures. We compare 3D reconstructions of the guinea pig inner ear, using light microscopy and orthogonal plane fluorescence optical sectioning microscopy. Applications of 3D reconstruction of the inner ear are further explored. For each method two bullas were prepared for 3D reconstruction. Both methods are explained. In general, the 3D reconstructions using orthogonal plane fluorescence optical sectioning microscopy are superior to light microscopy. The exact spiral shape of the cochlea could be reconstructed using orthogonal plane fluorescence optical sectioning microscopy and the length of the basilar membrane measured. When a resolution of 20 microm is sufficient, orthogonal plane fluorescence optical sectioning microscopy is a superior technique for 3D reconstruction of inner ear structures in animals.

A Bast-like valve in the pigeon?

The first description of the presence of a utriculo-endolymphatic valve in human fetuses was given by Bast in 1928. Since then this valve-like structure is called Bast's valve. Its exact function has not yet been established. The general opinion is that it has a protective function by having the possibility to separate the superior endolymphatic compartments of the labyrinth from the inferior compartment. Phylogenetically seen birds are the first vertebrates with a cochlear duct and a distinct inferior and superior part of the labyrinth. A structure in the pigeon inner ear, resembling Bast's valve in mammals, is described.

Munc18-1 promotes large dense-core vesicle docking.

Secretory vesicles dock at the plasma membrane before Ca(2+) triggers their exocytosis. Exocytosis requires the assembly of SNARE complexes formed by the vesicle protein Synaptobrevin and the membrane proteins Syntaxin-1 and SNAP-25. We analyzed the role of Munc18-1, a cytosolic binding partner of Syntaxin-1, in large dense-core vesicle (LDCV) secretion. Calcium-dependent LDCV exocytosis was reduced 10-fold in mouse chromaffin cells lacking Munc18-1, but the kinetic properties of the remaining release, including single fusion events, were not different from controls. Concomitantly, mutant cells displayed a 10-fold reduction in morphologically docked LDCVs. Moreover, acute overexpression of Munc18-1 in bovine chromaffin cells increased the amount of releasable vesicles and accelerated vesicle supply. We conclude that Munc18-1 functions upstream of SNARE complex formation and promotes LDCV docking.

Synaptic vesicles form by budding from tubular extensions of sorting endosomes in PC12 cells.

The putative role of sorting early endosomes (EEs) in synaptic-like microvesicle (SLMV) formation in the neuroendocrine PC12 cell line was investigated by quantitative immunoelectron microscopy. By BSA-gold internalization kinetics, four distinct endosomal subcompartments were distinguished: primary endocytic vesicles, EEs, late endosomes, and lysosomes. As in other cells, EEs consisted of vacuolar and tubulovesicular subdomains. The SLMV marker proteins synaptophysin and vesicle-associated membrane protein 2 (VAMP-2) localized to both the EE vacuoles and associated tubulovesicles. Quantitative analysis showed that the transferrin receptor and SLMV proteins colocalized to a significantly higher degree in primary endocytic vesicles then in EE-associated tubulovesicles. By incubating PC12 cells expressing T antigen-tagged VAMP (VAMP-TAg) with antibodies against the luminal TAg, the recycling pathway of SLMV proteins was directly visualized. At 15 degrees C, internalized VAMP-TAg accumulated in the vacuolar domain of EEs. Upon rewarming to 37 degrees C, the labeling shifted to the tubular part of EEs and to newly formed SLMVs. Our data delineate a pathway in which SLMV proteins together with transferrin receptor are delivered to EEs, where they are sorted into SLMVs and recycling vesicles, respectively.

Rab4 regulates formation of synaptic-like microvesicles from early endosomes in PC12 cells.

Early endosomes in PC12 cells are an important site for the formation of synaptic-like microvesicles and constitutive recycling vesicles. By immunogold electron microscopy, the small GTPase rab4 was localized to early endosomes and numerous small vesicles in the cell periphery and Golgi area of PC12 cells. Overexpression of GTPase-deficient Q67Lrab4 increased the number of early endosome-associated and cytoplasmic vesicles, whereas expression of GDP-bound S22Nrab4 significantly increased the length of early endosomal tubules. In parallel, Q67Lrab4 induced a shift in rab4, VAMP2, and TfR label from early endosomes to peripheral vesicles, whereas S22Nrab4 increased early endosome labeling of all three proteins. These observations were corroborated by early endosome budding assays. Together, our data document a thus far unrecognized role for rab4 in the formation of synaptic-like microvesicles and add to our understanding of the formation of constitutive recycling vesicles from early endosomes.

A cost-controlling treatment strategy of adding liraglutide to insulin in type 2 diabetes.

BACKGROUND: Addition of the GLP-1 receptor agonist liraglutide to insulin can reverse insulin-associated weight gain, improve HbA1c and decrease the need for insulin, but is expensive. From a cost perspective, such treatment should be discontinued when it is clear that treatment targets will not be achieved. Our aim was to find the best cost-controlling treatment strategy: the shortest possible trial period needed to discriminate successfully treated patients from those failing to achieve predefined targets of treatment success. METHODS: We used data from the 'Effect of Liraglutide on insulin-associated wEight GAiN in patients with Type 2 diabetes' (ELEGANT) trial, comparing additional liraglutide (n = 47) and standard insulin therapy (n = 24) during 26 weeks, to calculate the costs associated with different trial periods. Treatment success after 26 weeks was defined by having achieved ≥ 2 of the following: ≥ 4% weight loss, HbA1c ≤ 53 mmol/mol (7%), and/or discontinuation of insulin. RESULTS: The additional direct costs of adding liraglutide for 26 weeks were € 699 per patient, or € 137 per 1 kg weight loss, compared with standard therapy. The best cost-controlling treatment strategy (identifying 21 of 23 responders, treating four non-responders) was to continue treatment in patients showing ≥ 3% weight loss or ≥ 60% decrease in insulin dose at 8 weeks, with a total cost of € 246 for this t rial period, saving € 453 in case of early discontinuation. CONCLUSION: An 8-week trial period of adding liraglutide to insulin in patients with insulin-associated weight gain is an effective cost-controlling treatment strategy if the liraglutide is discontinued in patients not showing an early response regarding weight loss or insulin reduction.

Brain-derived Neurotrophic Factor (BDNF) and gray matter volume in bipolar disorder.

INTRODUCTION: Bipolar Disorder (BD) is a severe psychiatric condition characterized by grey matter (GM) volumes reduction. Neurotrophic factors have been suggested to play a role in the neuroprogressive changes during the illness course. In particular peripheral brain-derived neurotrophic factor (BDNF) has been proposed as a potential biomarker related to disease activity and neuroprogression in BD. The aim of our study was to investigate if serum levels of BDNF are associated with GM volumes in BD patients and healthy controls (HC). METHODS: We studied 36 inpatients affected by a major depressive episode in course of BD type I and 17 HC. Analysis of variance was performed to investigate the effect of diagnosis on GM volumes in the whole brain. Threshold for significance was P<0.05, Family Wise Error (FWE) corrected for multiple comparisons. All the analyses were controlled for the effect of nuisance covariates known to influence GM volumes, such as age, gender and lithium treatment. RESULTS: BD patients showed significantly higher serum BDNF levels compared with HC. Reduced GM volumes in BD patients compared to HC were observed in several brain areas, encompassing the caudate head, superior temporal gyrus, insula, fusiform gyrus, parahippocampal gyrus, and anterior cingulate cortex. The interaction analysis between BDNF levels and diagnosis showed a significant effect in the middle frontal gyrus. HC reported higher BDNF levels associated with higher GM volumes, whereas no association between BDNF and GM volumes was observed in BD. DISCUSSION: Our study seems to suggest that although the production of BDNF is increased in BD possibly to prevent and repair neural damage, its effects could be hampered by underlying neuroinflammatory processes interfering with the neurodevelopmental role of BDNF.

Munc18-1 phosphorylation by protein kinase C potentiates vesicle pool replenishment in bovine chromaffin cells.

Activation of protein kinase C (PKC) after robust stimulation is necessary for vesicle pool replenishment in secretory cells. Here we studied the contribution of a prominent downstream PKC target, Munc18-1, to this process in bovine chromaffin cells. In these cells, both activation of endogenous PKC and overexpressing of Munc18-1 promote vesicle pool replenishment after an extensive stimulation. In order to study the physiological relevance of PKC-dependent Munc18-1 phosphorylation, we generated two Munc18-1 phospho-mutants; one that mimics a constitutively PKC-phosphorylated Munc18-1 (i.e. a phosphomimetic mutant; Munc18-1(S313D)) and a second that cannot be PKC-phosphorylated (Munc18-1(3A)). Overexpression of Munc18-1(3A) caused a significant decrease in vesicle pool replenishment following a depleting stimulation, while Munc18-1(S313D) caused a significant increase in vesicle pool replenishment. These findings suggested that the phosphorylation of Munc18-1 by PKC potentiates vesicle pool replenishment. This hypothesis was further strengthened by the finding that overexpression of wild type Munc18-1 in the presence of a PKC inhibitor caused a significant reduction in vesicle pool replenishment, similar to that observed with Munc18-1(3A). Moreover, overexpression of Munc18-1(S313D) in the presence of the PKC inhibitor partly alleviated this attenuation, elucidating Munc18-1's unique contribution to vesicle pool replenishment. Finally, we demonstrate that Munc18-1 promotes vesicle docking in a phosphorylation-independent manner. This is deduced from the findings that both the wild type and the two Munc18-1 phospho-mutants enhanced docking to the same extent in bovine chromaffin cells. We conclude that Munc18-1 facilitates docking in a PKC phosphorylation-independent manner, and that its phosphorylation by PKC potentiates vesicle pool replenishment following a depleting stimulation, at a post-docking stage.