ABSTRACT
Autapses selectively form in specific cell types in many brain regions. Previous studies have also found putative autapses in principal spiny projection neurons (SPNs) in the striatum. However, it remains unclear whether these neurons indeed form physiologically functional autapses. We applied whole-cell recording in striatal slices and identified autaptic cells by the occurrence of prolonged asynchronous release (AR) of neurotransmitters after bursts of high-frequency action potentials (APs). Surprisingly, we found no autaptic AR in SPNs, even in the presence of Sr2+. However, robust autaptic AR was recorded in parvalbumin (PV)-expressing neurons. The autaptic responses were mediated by GABAA receptors and their strength was dependent on AP frequency and number. Further computer simulations suggest that autapses regulate spiking activity in PV cells by providing self-inhibition and thus shape network oscillations. Together, our results indicate that PV neurons, but not SPNs, form functional autapses, which may play important roles in striatal functions.
Subject(s)
Parvalbumins/metabolism , Corpus Striatum/metabolism , Interneurons/physiology , Neurons/metabolism , NeostriatumABSTRACT
Objective:To investigate the predictive value of abnormal heart rate circadian rhythm for all-cause mortality in stage 5 chronic kidney disease (CKD 5) patients.Methods:The retrospective study was performed in CKD 5 patients enrolled from the First Affiliated Hospital of Nanjing Medical University (Jiangsu Province Hospital) and the Affiliated BenQ Hospital of Nanjing Medical University from February, 2011 to December, 2019. A total of 159 healthy volunteers were enrolled as the healthy control group during the same period. The circadian rhythm of heart rate was monitored by 24-hour Holter. Related indices (including 24-hour, daytime and nighttime mean heart rate, night/day heart rate ratio, 24-hour maximum heart rate, 24-hour minimum heart rate and difference between maximum and minimum of 24-hour heart rate) were calculated. Non-dipping heart rate was defined as night/day heart rate ratio greater than 0.9. Cox regression model was used to analyze the risk factors of all-cause mortality in CKD 5 patients. Kaplan-Meier survival curve and Log-rank test were used to compare the differences of cumulative mortality between high ratio group (night/day heart rate ratio>0.91) and low ratio group (night/day heart rate ratio≤0.91). The nonlinear relationship between night/day heart rate ratio and all-cause mortality was analyzed by restricted cubic spline plot. Time-dependent receiver operating characteristic (ROC) curve was used to analyze the predictive value of night/day heart rate ratio for all-cause mortality in CKD 5 patients.Results:A total of 159 healthy volunteers and 221 CKD 5 patients were included in this study. There were 123 males (55.66%) and the age was (52.72±13.13) years old in CKD 5 patients. The total median follow-up time was 50.0 months. Compared with controls, 24-hour, nighttime mean heart rate, 24-hour minimum heart rate in CKD 5 patients were increased (all P<0.05), furthermore, the night/day heart rate ratio was higher [(0.91±0.09) vs (0.81±0.08), P<0.001], showing "non-dipping heart rate". However, the 24-hour maximum heart rate and the difference between maximum and minimum of 24-hour heart rate in CKD 5 patients were lower than controls (both P<0.05). Multivariate Cox regression analysis showed that the increased night/day heart rate ratio (per 0.1 increase, HR=1.557, 95% CI 1.073-2.258, P=0.020) was an independent influencing factor for all-cause mortality in CKD 5 patients. Kaplan-Meier survival curve analysis showed that the cumulative mortality of the high ratio group was significantly increased than that of the low ratio group (Log-rank test χ 2=7.232, P=0.007). From the restricted cubic spline plot, there was a linear effect between night/day heart rate ratio and all-cause mortality ( P=0.141), and when night/day heart rate ratio was above 0.91, the risk of all-cause mortality was significantly increased in CKD 5 patients. According to time-dependent ROC curve, the accuracy of night/day heart rate ratio in predicting all-cause mortality was 70.90% even when the survival time was up to 70.0 months. Conclusions:The circadian rhythm of heart rate in CKD 5 patients displays "non-dipping" state. High night/day heart rate ratio is an independent influencing factor for all-cause mortality in CKD 5 patients.