Plasma Proteolytic Cascade Activation during Neonatal Cardiopulmonary Bypass Surgery.

BACKGROUND: Neonates undergoing cardiopulmonary bypass (CPB) surgery to correct congenital heart defects often experience excessive bleeding. Exposure of blood to artificial materials during CPB may activate coagulation, complement and inflammatory pathways. In addition, the surgical stress placed on the haemostatic system may result in cross-activation of other plasma proteolytic cascades, which could further complicate physiological responses to the surgical procedure and post-operative recovery. Plasma protease inhibitors undergo distinct conformational changes upon interaction with proteases, and, thereby, can serve as endogenous biosensors to identify activation of the different proteolytic cascades. We tested the hypothesis that changes in the concentration and conformation of protease inhibitors regulating plasma proteolytic cascades during neonatal CPB are associated with post-operative bleeding. PATIENTS AND METHODS: Plasma samples from 44 neonates were obtained at four time points across the surgical procedure. Anti-thrombin, antitrypsin, anti-chymotrypsin, anti-plasmin, C1-inhibitor and tissue factor pathway inhibitor (TFPI) concentrations and conformations were evaluated by enzyme-linked immunosorbent assay, transverse urea gradient gel electrophoresis and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. RESULTS/CONCLUSION: The most striking changes were observed following heparin administration and were associated with the appearance of inactive forms of anti-thrombin and an increase in the plasma concentration of TFPI. Changes in anti-thrombin and TFPI remained evident throughout surgery and into the post-operative period but were not different between patients with or without post-operative bleeding. The concentration of antitrypsin decreased across surgery, but there was no significant accumulation of inactive conformations of any inhibitor besides anti-thrombin, indicating that widespread cross-activation of other plasma proteolytic cascades by coagulation proteases did not occur.

Comparison of the effects on brain stimulation reward of D1 blockade or D2 stimulation combined with AMPA blockade in the extended amygdala and nucleus accumbens.

This report compares the effects on medial forebrain bundle self-stimulation of injecting into either the sublenticular central extended amygdala (SLEAc) or nucleus accumbens shell (NAcS) the D1 dopamine receptor blocker SCH23390 or the D2 dopamine receptor agonist quinpirole alone or in combination with the AMPA glutamate receptor blocker NBQX. These manipulations all render affected neurons less excitable and therefore are expected to increase the stimulation pulse frequency required to maintain half-maximal response rate (required frequency, or RF). Injections were made ipsilateral and contralateral to the stimulation site but not bilaterally. Injecting quinpirole alone or in combination with NBQX was more effective in increasing RF than was injecting SCH23390 either alone or with NBQX. Quinpirole alone and in combination with NBQX was more effective when injected into the SLEAc than into the NAcS, and the combination injection was more effective than quinpirole alone, especially when injected into the SLEAc contralateral to the stimulation site. Maximum response rates were only modestly decreased by any drug injection. These data suggest a stronger role in brain stimulation reward for D2/glutamate than D1/glutamate interactions in the extended amygdala.