Persistence of quantal synaptic vesicle recycling in virtual absence of dynamins.

Dynamins are GTPases required for pinching vesicles off the plasma membrane once a critical curvature is reached during endocytosis. Here, we probed dynamin function in central synapses by depleting all three dynamin isoforms in postnatal hippocampal neurons down to negligible levels. We found a decrease in the propensity of evoked neurotransmission as well as a reduction in synaptic vesicle numbers. Recycling of synaptic vesicles during spontaneous or low levels of evoked activity were largely impervious to dynamin depletion, while retrieval of synaptic vesicle components at higher levels of activity was partially arrested. These results suggest the existence of balancing dynamin-independent mechanisms for synaptic vesicle recycling at central synapses. Classical dynamin-dependent mechanisms are not essential for retrieval of synaptic vesicle proteins after quantal single synaptic vesicle fusion, but they become more relevant for membrane retrieval during intense, sustained neuronal activity. KEY POINTS: Loss of dynamin 2 does not impair synaptic transmission. Loss of all three dynamin isoforms mostly affects evoked neurotransmission. Excitatory synapse function is more susceptible to dynamin loss. Spontaneous neurotransmission is only mildly affected by loss of dynamins. Single synaptic vesicle endocytosis is largely dynamin independent.

Evaluating the Impact of Psychiatric Disorders on Preoperative Pain Ratings, Narcotics Use, and the PROMIS-29 Quality Domains in Spine Surgery Candidates.

Objective We aimed to study the relationship between psychiatric Disorders (PD), preoperative pain, and opioid medication intake, as well as the quality of life patient-reported outcome measures using the Patient-Reported Outcomes Measurement Information System 29 (PROMIS-29) questionnaire, during the 30-day interval preceding surgery, in a consecutive series of patients who were scheduled to undergo surgical spine procedures. We hypothesized that PD could affect preoperative narcotic use and pain interference in a fashion that was not linearly associated with preoperative pain in spine surgery candidates. Methods The records of consecutive adult patients who underwent elective spinal surgery between October 2016 and August 2017 at a single institution were reviewed. We included patients who underwent preoperative pain assessment within 30 days prior to their planned surgery using the PROMIS-29 questionnaire. Patients with PD were compared to controls. Results A total of 117 patients matched our criteria. The average rating of pain intensity was notably higher in the PD group as compared to controls (p=0.004). The PD group had more patients complaining of high pain levels (>6) as compared to the control group (p=0.026). Controls with high pain levels had a greater incidence of preoperative narcotic use as compared to the low-pain cohort (p=0.029). However, there was no difference in the actual dose of daily narcotic medication taken between the PD and control groups (P=0.099) or between the low- and high pain score groups in the control (p=0.291) and PD (p=0.441) groups, respectively. Patients with PD and higher pain ratings seemed to have a higher incidence of anxiety (p=0.005) and depression (p<0.001). That was not the case for controls. Conclusions PDs may impact the degree of preoperative pain interference and the intake of narcotic medication independently from pain intensity ratings.

Smoking has a dose-dependent effect on the incidence of preoperative opioid consumption in female geriatric patients with spine disease.

Tobacco use and narcotic medication have been associated with worse functional outcomes after surgery. Our goal was to investigate potential associations between smoking and preoperative opioid consumption in a geriatric population undergoing spine surgery, and their impact on postoperative outcomes. The records of 536 consecutive patients aged more than 65 years who underwent elective spinal surgery between November 2014 and August 2017 at a single institution were reviewed. Primary outcomes included rates of preoperative opioid consumption and postoperative hospital length of stay and complications. Males were more likely to be smokers than females (p < 0.001), whereas females were more likely to take opioid analgesics preoperatively (p = 0.022). Women with a history of smoking were more likely to have increased preoperative opioid consumption compared to those with no history of smoking (63.64% vs. 42.04%; p < 0.001). Such a relationship was not found in men. Subgroups analysis of female patients with a history of tobacco use comparing current and former smoker status showed that both groups exhibited increased preoperative opioid consumption compared to patients who never smoked (88.89% vs 42.04%; p < 0.001 for current users; 59.42% vs 42.04% for former users; p = 0.008). There was also a dose-depended relationship between smoking and increased preoperative opioid consumption. Geriatric female spine patients with a history of smoking have a higher incidence of preoperative opioid consumption. Opioid intake appears to increase with the number of pack-years, both in patients with a history of smoking and in those who currently smoke.

Electronic Communication Patterns Could Reflect Preoperative Anxiety and Serve as an Early Complication Warning in Elective Spine Surgery Patients with Affective Disorders: A Retrospective Analysis of a Cohort of 1199 Elective Spine Patients.

OBJECTIVE: The analysis of perioperative electronic patient portal (EPP) communication may provide risk stratification and insight for complication prevention in patients with affective disorders (ADs). We aimed to understand how patterns of EPP communication in patients with AD relate to preoperative narcotic use, surgical outcomes, and readmission rates. METHODS: The records of adult patients who underwent elective spinal surgery between January 2010 and August 2017 at a single institution were retrospectively reviewed for analysis. Primary outcomes included preoperative narcotic use, the number of perioperative EPP messages sent, rates of perioperative complications, hospital length of stay, emergency department (ED) visits within 6 weeks, and readmissions within 30 days after surgery. RESULTS: A total of 1199 patients were included in the analysis. Patients with an AD were more likely to take narcotics before surgery (51.69% vs. 41%, P < 0.001) and to have active EPP accounts (75.36% vs. 69.75%, P = 0.014) compared with controls. They were also more likely to send postoperative messages (38.89% vs. 32.75%, P = 0.030) and tended to send more messages (0.67 vs. 0.48, P = 0.034). The AD group had higher rates of postoperative complications (8.21% vs. 3.98%, P = 0.001), ED visits (4.99% vs. 2.43%, P = 0.009), and readmissions postoperatively (2.49% vs. 1.38%, P = 0.049). CONCLUSIONS: AD patients have specific patterns of perioperative EPP communication. They are at a higher risk of postoperative complications. Addressing these concerns early may prevent more serious morbidity and avoid unnecessary ED visits and readmissions, thus reducing costs and improving patient care.

Synaptic vesicle pool-specific modification of neurotransmitter release by intravesicular free radical generation.

KEY POINTS: Synaptic transmission is mediated by the release of neurotransmitters from synaptic vesicles in response to stimulation or through the spontaneous fusion of a synaptic vesicle with the presynaptic plasma membrane. There is growing evidence that synaptic vesicles undergoing spontaneous fusion versus those fusing in response to stimuli are functionally distinct. In this study, we acutely probe the effects of intravesicular free radical generation on synaptic vesicles that fuse spontaneously or in response to stimuli. By targeting vesicles that preferentially release spontaneously, we can dissociate the effects of intravesicular free radical generation on spontaneous neurotransmission from evoked neurotransmission and vice versa. Taken together, these results further advance our knowledge of the synapse and the nature of the different synaptic vesicle pools mediating neurotransmission. ABSTRACT: Earlier studies suggest that spontaneous and evoked neurotransmitter release processes are maintained by synaptic vesicles which are segregated into functionally distinct pools. However, direct interrogation of the link between this putative synaptic vesicle pool heterogeneity and neurotransmission has been difficult. To examine this link, we tagged vesicles with horseradish peroxidase (HRP) - a haem-containing plant enzyme - or antibodies against synaptotagmin-1 (syt1). Filling recycling vesicles in hippocampal neurons with HRP and subsequent treatment with hydrogen peroxide (H2 O2 ) modified the properties of neurotransmitter release depending on the route of HRP uptake. While strong depolarization-induced uptake of HRP suppressed evoked release and augmented spontaneous release, HRP uptake during mild activity selectively impaired evoked release, whereas HRP uptake at rest solely potentiated spontaneous release. Expression of a luminal HRP-tagged syt1 construct and subsequent H2 O2 application resulted in a similar increase in spontaneous release and suppression as well as desynchronization of evoked release, recapitulating the canonical syt1 loss-of-function phenotype. An antibody targeting the luminal domain of syt1, on the other hand, showed that augmentation of spontaneous release and suppression of evoked release phenotypes are dissociable depending on whether the antibody uptake occurred at rest or during depolarization. Taken together, these findings indicate that vesicles that maintain spontaneous and evoked neurotransmitter release preserve their identity during recycling and syt1 function in suppression of spontaneous neurotransmission can be acutely dissociated from syt1 function to synchronize synaptic vesicle exocytosis upon stimulation.

Imaging Synaptic Vesicle Exocytosis-Endocytosis with pH-Sensitive Fluorescent Proteins.

The introduction of pHluorin, a pH-sensitive GFP, by Miesenbock and colleagues provided a versatile tool to studies of vesicle trafficking, in particular synaptic vesicle exocytosis and endocytosis. By tagging pHluorin to the luminal region of the synaptic vesicular protein synaptobrevin (also called VAMP, vesicle-associated membrane protein) or other synaptic vesicle-specific proteins such as the vesicular glutamate transporter-1, we are able to directly track synaptic vesicle endocytosis in response to stimuli in a molecularly specific manner. Here, we describe the process of imaging synaptic vesicle endocytosis in response to extracellular stimulation in dissociated neuronal cultures of hippocampal neurons obtained from rats-also applicable to mice-using pHluorin-tagged vesicular glutamate transporter-1 as a reporter.

One month in the life of a neuron: longitudinal single-unit electrophysiology in the monkey visual system.

Conventional recording methods generally preclude following the activity of the same neurons in awake animals across days. This limits our ability to systematically investigate the principles of neuronal specialization, or to study phenomena that evolve over multiple days such as experience-dependent plasticity. To redress this shortcoming, we developed a drivable, chronically implanted microwire recording preparation that allowed us to follow visual responses in inferotemporal (IT) cortex in awake behaving monkeys across multiple days, and in many cases across months. The microwire bundle and other implanted components were MRI compatible and thus permitted in the same animals both functional imaging and long-term recording from multiple neurons in deep structures within a region the approximate size of one voxel (<1 mm). The distinct patterns of stimulus selectivity observed in IT neurons, together with stable features in spike waveforms and interspike interval distributions, allowed us to track individual neurons across weeks and sometimes months. The long-term consistency of visual responses shown here permits large-scale mappings of neuronal properties using massive image libraries presented over the course of days. We demonstrate this possibility by screening the visual responses of single neurons to a set of 10,000 stimuli.