Dexmedetomidine attenuates motor deficits via restoring the function of neurons in the nigrostriatal circuit in Parkinson's disease model mice

Dexmedetomidine, an alpha-2 adrenoceptors agonist, provides a neuroprotective effect for dopaminergic neurons in the substantia nigra and attenuates glucose imbalance in the 6-hydroxydopamine animal model of Parkinson's disease

INTRODUCTION

Studies have shown that dexmedetomidine (DEX, an a2-adrenoceptors agonist) provides a neuroprotective effect and influences blood glucose levels. Here, we evaluated the effect of prolonged treatment with low doses of DEX on the survival rate of dopaminergic (DAergic) neurons in the substantia nigra and also serum glucose levels in 6-hydroxydopamine (6-OHDA) - induced Parkinson's disease (PD) in the rat.

MATERIAL AND METHODS

The neurotoxin of 6-OHDA was injected into the medial forebrain bundle by stereotaxic surgery. DEX (25 and 50 µg/kg, i.p) and yohimbine, an a2-adrenoceptor antagonist (1 mg/kg, i.p) were administered before the surgery to the 13 weeks afterward. Apomorphine-induced rotational tests and blood sampling were carried out before the surgery and multiple weeks after that. Thirteen weeks after the surgery, the rats' brain was transcardially perfused to assess the survival rate of DAergic neurons using the tyrosine hydroxylase (TH) immunohistochemistry.

RESULTS

DEX remarkably attenuated the severity of rotational behavior and reversed the progress of the PD. It also increased the number of TH-labeled neurons by up to 60%. The serum glucose levels in 6-OHDA-received rats did not change in the third and seventh weeks after the surgery but decreased significantly in the thirteenth week. Treatment with DEX prevented this decrement in glucose levels. On the other hand, Treatment with yohimbine did not affect PD symptoms and glucose levels.

CONCLUSION

Our data indicate that DEX through neuroprotective activity attenuates the severity of 6-OHDA-induced PD in rats. DEX might also prevent hypoglycemia during the progress of the PD.

Effects of dexmedetomidine dosage on the short-term cognitive function of elderly patients undergoing cardiac surgery

BACKGROUND

This study aimed to investigate the effects of perioperative dexmedetomidine (DEX) infusion rates on the postoperative short-term cognitive function.

METHODS

A total of 88 patients aged ≥ 60 years who underwent cardiac surgery from January 2022 to November 2022 at the First Affiliated Hospital of The University of Science and Technology of China (USTC) were included. Based on a single-center pilot analysis, patients were divided into two groups according to the rate of intraoperative DEX infusion, which started after tracheal intubation and continued until 1 h before extubation in the cardiac surgery intensive care unit. In Group L (n = 44), the infusion rate was 0.1-0.5 µg/kg/h (low-dose group), whereas in Group H (n = 44), the infusion rate was 0.5-0.9 µg/kg/h (high-dose group). Clinical outcomes were then compared between the groups. The Mini-Mental State Evaluation (abbreviated as MMSE1, MMSE2, MMSE3, and MMSE4) scale was used for the assessment of cognitive function, which was conducted on postoperative Days 2 (T1), 7 (T2), 14 (T3), and 28 (T4), with the score from postoperative Day 2 (MMSE1) considered as the primary observation.

RESULTS

Patients in Group L had higher MMSE1 scores compared to those in Group H (26.0 [24.0, 27.0] vs. 24.5 [22.0, 26.0], p = 0.046), and there was no significant difference in the scores between the groups at all subsequent time points. Group H exhibited a higher incidence of hypotension and bradycardia compared to Group L (p = 0.044 and p = 0.047, respectively).

CONCLUSIONS

Compared to a high dose (0.5-0.9 µg/kg/h) of DEX infusion, a low-dose (0.1-0.5 µg/kg/h) infusion started after induction of anesthesia and continued until 1 h before extubation improved postoperative cognitive function scores on postoperative Day 2 in patients aged 60 years and older.

TRIAL REGISTRATION

URL: www.chictr.org.cn with registration number ChiCTR2100055093, registered on 31/12/2021.

Construction and evaluation of an alcohol vapor chamber system

An increasing number of studies demonstrated that alcohol vapor chamber is an effective way to model physical signs of alcohol use disorders. Although researchers are developing different vapor chambers to study chronic alcohol exposure model worldwide, few studies build and modify their own vapor chambers in China. Here, we designed and established an alcohol vapor chamber system for small animals. We described a paradigm showing how to control and monitor alcohol concentration in whole system. The vapor chamber system with several advantages including accommodating up to ten standard mouse cages. Furthermore, the system was tested by evaluating the blood alcohol concentration and neuron injury in mice. Importantly, the alcohol withdrawal after vapor exposure caused motor coordination impairment, anxiolytic- and depression-like behavior. Finally, the N-methyl-D-aspartate receptor (NMDAR)-mediated glutamatergic transmissions in the medial prefrontal cortex was changed after alcohol vapor exposure-induced behaviors. The frequency and amplitude of spontaneous excitatory postsynaptic currents between control and alcohol groups were not different, suggesting that alcohol exposure-induced behaviors are associated with the change in NMDAR response. Taken together, the new alcohol vapor chamber system was constructed, which would help to research the relationship between the stable alcohol exposure and withdrawal behaviors and to study chronic alcohol exposure-induced disorders in China.