Hyperalgesia caused by nerve transection: long-lasting block prevents early hyperalgesia in the receptive field of the surviving nerve

[Postoperative pain therapy in Germany. Status quo]

A great deal of progress has been made in the field of postoperative pain therapy in the last 20 years. Beginning from clinical trials on the effectiveness of individual procedures, such as epidural anesthesia and patient-controlled analgesia, a wide range of healthcare services research as well as basic research with human and animal experiments has been established. Whereas health services research in the 1980s and 1990s focused more on the implementation of acute pain services, outcome-oriented research approaches are nowadays the center of attention. Acute pain registries and pain certification projects initiated in Germany have to be mentioned particularly in this respect. Basic research papers from recent years increasingly address specific aspects of acute postoperative pain and have provided translational approaches that are applied around the world for studying neurobiological mechanisms of postoperative pain. At the same time, interdisciplinary cooperation in research projects has led to a better understanding of complex correlations regarding predictors and mechanisms (including psychosocial aspects) of acute and in recent times also chronic pain after surgery. In parallel, evidence-based medicine has found its way into acute pain medicine in Germany. In 2007, clinical acute pain therapy in Germany was enhanced by S3 level guidelines for the first time; however, the implementation is still incomplete. In future, questions concerning mechanism-based therapy of acute pain need to be equally in the center of attention of research, such as prevention of persisting pain after surgery and acute pain of different origins.

Cyclic nucleotide-gated channel block by hydrolysis-resistant tetracaine derivatives

To meet a pressing need for better cyclic nucleotide-gated (CNG) channel antagonists, we have increased the biological stability of tetracaine-based blockers by synthesizing amide and thioamide linkage substitutions of tetracaine (1) and a higher affinity octyl tail derivative (5). We report the apparent K(D) values, the mechanism of block, and the in vitro hydrolysis rates for these compounds. The ester linkage substitutions did not adversely affect CNG channel block; unexpectedly, thioamide substitution in 1 (compound 8) improved block significantly. Furthermore, the ester linkage substitutions did not appear to affect the mechanism of block in terms of the strong state preference for closed channels. All ester substituted compounds, especially the thioamide substitutions, were more resistant to hydrolysis by serum cholinesterase than their ester counterparts. These findings have implications for dissecting the physiological roles of CNG channels, treating certain forms of retinal degeneration, and possibly the current clinical uses of compound 1.