Neonatal anesthesia impairs synapsin 1 and synaptotagmin 1, two key regulators of synaptic vesicle docking and fusion

Abstract

Early exposure to anesthetics may interfere with synaptic development and lead to cognitive deficits. We previously demonstrated a decrease in vesicles docked at and within 100 nm from the presynaptic membrane in hippocampal nerve terminals of neonatal rats after anesthesia. Hence, we designed this study to assess the effects of neonatal anesthesia on Synapsin 1 (Syn 1) and Synaptotagmin 1 (Syt 1), two key regulators of vesicle docking and fusion. To test the link between changes in Syn 1 and Syt 1 and behavioral deficits observed after neonatal anesthesia, we also assessed retention memory and fear conditioning in adolescent rats after neonatal anesthesia. Pups received a combination of clinical anesthetics, then Syn 1 and Syt 1 mRNA and protein expression were determined at the peak (postnatal day 8, P8), part-way through (P12) and end of synaptogenesis (P24) in the CA1-subiculum by qPCR and Western Blotting. Anesthesia decreased Syn1 and Syt1 mRNA expression at P8 (p<0.01 and p<0.001) and P12 (p=0.001 and p=0.017), but not P24 (p=0.538 and p=0.671), and impaired Syn1, p-Syn1 and Syt1 protein levels at P8 (p=0.038, p=0.041 and p=0.004, respectively), P12 (p<0.001, p=0.001 and p<0.0001) and P24 (p=0.025, p=0.031 and p=0.001). Anesthetic-challenged rats displayed deficient long-term retention memory (p=0.019) and hippocampus-dependent fear conditioning (p<0.001). These results suggest that anesthetics alter Syn 1 and Syt 1 during synapse assembly and maturation, raising the possibility that anesthetic interference with Syn 1 and Syt 1 could initiate changes in synaptic function that contribute to the cognitive deficits observed after neonatal anesthesia.

Surgery, Anesthesia and Intensive Care Environment Induce Delirium-Like Behaviors and Impairment of Synaptic Function-Related Gene Expression in Aged Mice

“…Hippocampal total RNA was extracted from control (pooled N = 3) and A/S/I animals (pooled N = 3). cDNA synthesis was performed as previously described ( Atluri et al, 2019 ). cDNA template (100 ng/well) was mixed with SsoAdvanced SYBR green 2× master mix and loaded (20 μl/per well) on predesigned 96-well qPCR array plates.…”

“…Western blot analysis was performed as described previously ( Atluri et al, 2019 ). Briefly, hippocampal tissue from control ( N = 5–7) and A/S/I animals ( N = 5-7) was lysed in 0.2 ml ice-cold RIPA buffer in the presence of protease and phosphatase inhibitor cocktails (Thermo Scientific, United States).…”

Neonatal exposures to sevoflurane in rhesus monkeys alter synaptic ultrastructure in later life

“…Exposure of rodents to anesthesia in infancy causes a deterioration of synaptic signaling, as evidenced by suppressed long-term potentiation (LTP), 32 , 36 , 37 , 38 , 39 inhibited vesicular exocytosis, 40 and altered expression of vesicular docking proteins. 41 , 42 Neonatal anesthesia exposures in rodents alter the overall density of synapses in the hippocampus and subiculum, 43 , 44 , 45 reduce large mushroom spines 38 associated with perforated synapses and LTP, 46 and drive proliferation of smaller immature spines and filopodia. 47 , 48 , 49 , 50 These synaptic changes after anesthesia exposure in infancy are a potential mechanism for behavioral disturbances later in life.…”

Neonatal exposures to sevoflurane in rhesus monkeys alter synaptic ultrastructure in later life

“…Hippocampal damage is behaviorally suggested in the present cohort because impairments in visual recognition and disrupted socioemotional behaviors follow neonatal hippocampal lesions (Raper et al, 2017; Zeamer et al, 2010). Further, the effects of early-life anesthesia in the primate CA1 may mirror synaptic impacts of neonatal anesthesia in the rodent CA1, including short- and long-term downregulation of LTP, impaired vesicle docking, and synapse loss (Atluri et al, 2019; De Roo et al, 2009; Schaefer et al, 2020; Wu et al, 2016; H. Zhang et al, 2015).…”

“…Synapses are one likely substrate for the long-term effects of anesthesia on behavior. Exposure of rodents to anesthesia in infancy cause a deterioration of synaptic signaling, as evinced by suppressed long-term potentiation (LTP) (Guo et al, 2018; Jevtovic-Todorovic et al, 2003; Kato et al, 2013; Schaefer et al, 2020; Sun et al, 2020), inhibited vesicular exocytosis (Baumgart et al, 2015), and altered expression of vesicular docking proteins (Atluri et al, 2019; Xiao et al, 2016). Neonatal anesthesia exposures also alter the overall density of synapses in the hippocampus and subiculum of rodents (Amrock et al, 2015; Ju et al, 2019; Lunardi et al, 2010), and could impact the morphology of remaining synapses.…”