GABAA Receptor Benzodiazepine Binding Sites and Motor Impairments in Parkinson's Disease

Flumazenil is an allosteric modulator of the γ-aminobutyric acid-A receptor (GABAAR) benzodiazepine binding site that could normalize neuronal signaling and improve motor impairments in Parkinson's disease (PD). Little is known about how regional GABAAR availability affects motor symptoms. We investigated the relationship between regional availability of GABAAR benzodiazepine binding sites and motor impairments in PD. Methods: A total of 11 Patients with PD (males; mean age 69.0 ± 4.6 years; Hoehn and Yahr stages 2-3) underwent [11C]flumazenil GABAAR benzodiazepine binding site and [11C]dihydrotetrabenazine vesicular monoamine transporter type-2 (VMAT2) PET imaging and clinical assessment. Stepwise regression analysis was used to predict regional cerebral correlates of the four cardinal UPDRS motor scores using cortical, striatal, thalamic, and cerebellar flumazenil binding estimates. Thalamic GABAAR availability was selectively associated with axial motor scores (R2 = 0.55, F = 11.0, β = -6.4, p = 0.0009). Multi-ligand analysis demonstrated significant axial motor predictor effects by both thalamic GABAAR availability (R2 = 0.47, β = -5.2, F = 7.2, p = 0.028) and striatal VMAT2 binding (R2 = 0.30, β = -3.9, F = 9.1, p = 0.019; total model: R2 = 0.77, F = 11.9, p = 0.0056). Post hoc analysis demonstrated that thalamic [11C]methyl-4-piperidinyl propionate cholinesterase PET and K1 flow delivery findings were not significant confounders. Findings suggest that reduced thalamic GABAAR availability correlates with worsened axial motor impairments in PD, independent of nigrostriatal degeneration. These findings may augur novel non-dopaminergic approaches to treating axial motor impairments in PD.

Challenges and innovations in brain PET analysis of neurodegenerative disorders: a mini-review on partial volume effects, small brain region studies, and reference region selection

Positron Emission Tomography (PET) brain imaging is increasingly utilized in clinical and research settings due to its unique ability to study biological processes and subtle changes in living subjects. However, PET imaging is not without its limitations. Currently, bias introduced by partial volume effect (PVE) and poor signal-to-noise ratios of some radiotracers can hamper accurate quantification. Technological advancements like ultra-high-resolution scanners and improvements in radiochemistry are on the horizon to address these challenges. This will enable the study of smaller brain regions and may require more sophisticated methods (e.g., data-driven approaches like unsupervised clustering) for reference region selection and to improve quantification accuracy. This review delves into some of these critical aspects of PET molecular imaging and offers suggested strategies for improvement. This will be illustrated by showing examples for dopaminergic and cholinergic nerve terminal ligands.

Endothelin-A receptor antagonism improves small bowel graft perfusion and structure after ischemia and reperfusion

BACKGROUND

We hypothesized that endothelin-A (ET-A) receptor activation plays a central role in intestinal ischemia-reperfusion-induced hemodynamic changes and may trigger the process of mucosal barrier destruction. Our aims were to investigate and compare the effects of systemic and intragraft ET-A receptor antagonist therapy during the early revascularization phase of small bowel transplants.

METHODS

In Groups 1, 2, and 3 orthotopic small bowel autotransplants were performed in anesthetized dogs. Group 4 served as sham-operated control. Group 2 was treated i.v. with the ET-A receptor antagonist ETR-p1/fl peptide at the onset of reperfusion. In Group 3, intragraft infusion of the ETR-p1/fl peptide was applied during cold ischemia. The mucosal myeloperoxidase activity and the free radical-producing capacity of the granulocytes passing the intestinal graft were determined, and the systemic hemodynamic features were recorded. The extent of the mucosal injury was determined from tissue biopsies taken after 4 hr of reperfusion.

RESULTS

Reperfusion progressively decreased the mesenteric blood flow, increased the mesenteric vascular resistance, and enhanced the accumulation and free radical production capacity of the leukocytes. These changes were significantly inhibited in Group 2 with systemic (i.v.) administration of the ET-A receptor antagonist. The local, intragraft treatment improved the mesenteric hemodynamic changes and decreased the accumulation but not the activation of the circulating leukocytes. The structural injury of the graft was prevented in both treated groups.

CONCLUSIONS

Endothelins are involved in the hemodynamic events leading to structural injury of the intestinal graft after ischemia-reperfusion. The antagonism of intestinal ET-A receptors by a combination of local and systemic drug delivery offers a rational treatment modality in these conditions.

[Laparoscopic cholecystectomy: analysis of 1122 operations]

The results of 1122 laparoscopic cholecystectomies have been analyzed which were performed within a two year period of time. In 1097 (97.8%) cases the authors managed to carry out the laparoscopic procedure, however in 25 patients (2.2%) the operation had to be converted to an open surgery. There was no hospital mortality, however 1 patient died at home due to pulmonary embolism. (Mortality: 0.09%) According to their survey 758 patients exhibited concurrent medical risk factors and 413 previous abdominal operations increased the "surgical" risk of laparoscopic procedures. 27 early and 46 late postoperative complications have been observed. In 3 instances (0.26%) bile duct injury occurred and in 5 cases (0.44%) reoperations had to be carried out secondary to postoperative complications. Forty patients (3.6%) have had recognized common bile duct stones, these were removed, in part preoperatively (28pts), in part postoperatively (11pts) by endoscopic sphincterotomy (EST). In one case a laparoscopic retrieval of common bile duct stone was accomplished via the dilated cystic duct. 47% of their patients left the hospital on the first day and 78% of them were discharged within 2 days.