Antidepressant-Like and Anxiolytic-Like Effects of ZBD-2, a Novel Ligand for the Translocator Protein (18 kDa).

Activation of translocator protein (18 kDa) (TSPO) plays an important role to mediate rapid anxiolytic efficacy in stress response and stress-related disorders by the production of neurosteroids. However, little is known about the ligand of TSPO on the anxiety-like and depressive behaviors and the underlying mechanisms in chronic unpredictable mild stress (UCMS) mice. In the present study, a novel ligand of TSPO, ZBD-2 [N-benzyl-N-ethyl-2-(7,8-dihydro-7-benzyl-8-oxo-2-phenyl-9H-purin-9-yl) acetamide] synthesized by our laboratory, was used to evaluate the anxiolytic and antidepressant efficacy and to elucidate the underlying mechanisms. ZBD-2 (3 mg/kg) significantly attenuated anxiety-like and depressive behaviors in the UCMS mice, which was blocked by TSPO antagonist PK11195 (3 mg/kg). Treatment of ZBD-2 reversed the decrease in biogenic amines (norepinephrine, dopamine, and serotonin) in the brain region of hippocampus in the UCMS mice. The decreases in TSPO, GluN2B-containing N-methyl-D-aspartate (NMDA) receptors, GluA1, p-GluA1-Ser831, p-GluA1-Ser845, PSD-95, and GABAA-a2 were integrated with the increases of CaMKII and iNOS levels in the hippocampus of the UCMS mice. ZBD-2 significantly reversed the changes of above proteins. However, ZBD-2 or PK11195 treatment did not affect the levels of GluN2A-containing NMDA receptors and the total levels of GAD67. Our study provides strong evidences that ZBD-2 has a therapeutic effect on chronic stress-related disorders such as depression and anxiety through regulating the biogenic amine levels and the synaptic proteins in the hippocampus.

Site-specific effect of guanosine 3',5'-cyclic monophosphate phosphodiesterase inhibition in isolated lamb lungs.

OBJECTIVE: To determine the effect of combining inhaled nitric oxide (NO) with an inhibitor of guanosine 3',5'-cyclic monophosphate-specific phosphodiesterase on total and segmental lung resistances. STUDY DESIGN: A controlled laboratory study in isolated blood-perfused lungs prepared from lambs. SETTING: Animal research facility affiliated with a university teaching hospital. SUBJECTS: Five newborn lambs at <48 hrs of life. INTERVENTIONS: Isolated blood-perfused lungs were prepared and treated with indomethacin (40 microg/mL) to inhibit prostaglandin synthesis. After a baseline period of normoxia (28% oxygen), pulmonary hypertension was induced with the thromboxane mimetic U46619 (0.1-0.4 microg/kg/min). During pulmonary hypertension, lungs were studied with inhaled NO only, with infusion of zaprinast only (0.25 mg/kg bolus and 0.05 mg/kg/min infusion), and with a combination of the two. For each study condition, the total pressure decrease across the lung was measured, and the inflow-outflow occlusion technique was used to partition the total pressure gradient measured at constant flow (100 mL/kg/min) into gradients across relatively noncompliant large arteries and veins and more compliant small arteries and veins. MEASUREMENTS AND MAIN RESULTS: U46619 infusion produced significant pulmonary vasoconstriction. The combination of inhaled NO and zaprinast decreased the total pressure decrease across the lung significantly more than NO alone. This effect was primarily attributable to a significantly greater decrease in gradient across the small artery segment after inhaled NO and zaprinast compared with NO alone. CONCLUSIONS: Guanosine 3',5'-cyclic monophosphate phosphodiesterase inhibition with zaprinast enhances the effect of inhaled NO, particularly in conditions in which small arteries represent the site of resistance. Phosphodiesterase inhibition may be a promising adjunct to inhaled NO for the treatment of persistent pulmonary hypertension.

The cGMP phosphodiesterase inhibitor zaprinast enhances the effect of nitric oxide.

We investigated the effect of zaprinast (M&B 22948), a specific cGMP phosphodiesterase inhibitor, on pulmonary arteries isolated from lambs with persistent pulmonary hypertension following prenatal ligation of the ductus arteriosus. Relaxations to sodium nitroprusside, which donates nitric oxide inside the smooth muscle cell, were significantly decreased in pulmonary arteries from ligated lambs. Pretreatment with 3 x 10(-5) M zaprinast restored them to levels close to those observed in untreated arteries from control animals. Further studies in intact newborn lambs were then conducted under three experimental conditions: (1) NO inhalation at 6 ppm, (2) zaprinast infusion at 0.05 mg/kg/min, and (3) combination therapy of zaprinast infusion in addition to inhaled NO at 6 ppm. Combined therapy with NO and zaprinast decreased the pulmonary artery pressure (34.3 +/- 3%) and pulmonary vascular resistance (64 +/- 7%) and increased pulmonary blood flow (88 +/- 34%) and postductal PaO2 (287 +/- 34%) to a significantly greater extent than NO alone, zaprinast alone, or the sum of these two responses, indicating a true synergistic effect. Zaprinast pretreatment also markedly increased the duration of pulmonary vasodilation to nitric oxide. There was no effect on systemic blood pressure with the combined therapy. We conclude that zaprinast pretreatment significantly enhances the effect of sodium nitroprusside on isolated pulmonary arteries, as well the effect of inhaled NO at 6 ppm in newborn lambs with persistent pulmonary hypertension. We speculate that phosphodiesterase inhibition may increase the response rate to NO or allow the use of much lower inhaled concentrations of NO.