Biosynthesis, mode of action, and functional significance of neurosteroids in the purkinje cell.

The brain has traditionally been considered to be a target site of peripheral steroid hormones. In addition to this classical concept, we now know that the brain has the capacity to synthesize steroids de novo from cholesterol, the so-called "neurosteroids." In the middle 1990s, the Purkinje cell, an important cerebellar neuron, was identified as a major site for neurosteroid formation in the brain of mammals and other vertebrates. This discovery has provided the opportunity to understand neuronal neurosteroidogenesis in the brain. In addition, biological actions of neurosteroids are becoming clear by the studies using the Purkinje cell, an excellent cellular model, which is known to play an important role in memory and learning processes. Based on the studies on mammals over the past decade, it is considered that the Purkinje cell actively synthesizes progesterone and estradiol from cholesterol during neonatal life, when cerebellar neuronal circuit formation occurs. Both progesterone and estradiol promote dendritic growth, spinogenesis, and synaptogenesis via each cognate nuclear receptor in the developing Purkinje cell. Such neurosteroid actions mediated by neurotrophic factors may contribute to the formation of cerebellar neuronal circuit during neonatal life. 3α,5α-Tetrahydroprogesterone (allopregnanolone), a progesterone metabolite, is also synthesized in the cerebellum and considered to act as a survival factor of Purkinje cells in the neonate. This review summarizes the current knowledge regarding the biosynthesis, mode of action, and functional significance of neurosteroids in the Purkinje cell during development in terms of synaptic formation of cerebellar neuronal networks.

[Blood lactate levels during fast-track cardiac anesthesia].

BACKGROUND: Lactate is a very sensitive marker of outcomes in critically ill patients. The aim of this study was to investigate the significance of blood lactate measurement during fast-track cardiac anesthesia. METHODS: We examined arterial blood lactate levels of 12 patients following coronary artery bypass graft surgery under intermittent aortic cross clamping with fast-track cardiac anesthesia. Anesthesia was induced with propofol and fentanyl, and maintained with propofol, fentanyl (total 400-1000 micrograms) and isoflurane. Blood samples were collected from a radical artery catheter. RESULTS: At the termination of the extracorporeal circulation, the blood lactate was 10.3 +/- 2.0 (7.4-12.5) mmol.l-1. This value decreased slowly to 1.5 +/- 0.4 mmol.l-1 on the second postoperative day. All patients were extubated within 4 hours after surgery. Vital signs were stable, and no cardiac events occurred perioperatively. CONCLUSIONS: A continuous decline in blood lactate levels was related to a favorable postoperative course. Further research might be required to prevent transient hyperlactecemia at the end of cardiopulmonary bypass.