Practical mechanical threshold estimation in rodents using von Frey hairs/Semmes-Weinstein monofilaments: Towards a rational method.

Here, we reconsider the status quo in testing mechanical sensitivity with von Frey's hairs. The aim is to improve paw withdrawal estimates by integrating current psychometric theory, and to maximise the clinical relevance and statistical power of mechanosensory models. A wealth of research into human tactile stimulus perception may be extended to the quantification of laboratory animal behaviour. We start by reviewing each step of the test, from its design and application through to data analysis. Filament range is assessed as a whole; possible test designs are compared; techniques of filament application to mice and rats are considered; curve fitting software is introduced; possibilities for data pooling and curve fitting are evaluated. A rational update of classical methods in line with recent advances in psychometrics and supported by open source software is expected to improve data homogeneity, and Reduce and Refine animal use in accord with the '3R' principles.

The effects of L-NAME on neuronal NOS and SOD1 expression in the DRG-spinal cord network of axotomised Thy 1.2 eGFP mice.

Nitric oxide (NO) plays an important role in pathophysiology of the nervous system. Copper/zinc superoxide dismutase (SOD1) reacts with superoxide, which is also a substrate for NO, to provide antioxidative protection. NO production is greatly altered following nerve injury, therefore we hypothesised that SOD1 and NO may be involved in modulating axotomy responses in dorsal root ganglion (DRG)-spinal network. To investigate this interaction, adult Thy1.2 enhanced membrane-bound green fluorescent protein (eGFP) mice underwent sciatic nerve axotomy and received NG-nitro- 

How do the satellite glia cells of the dorsal root ganglia respond to stressed neurons?--nitric oxide saga from embryonic development to axonal injury in adulthood.

Dorsal root ganglia (DRG) respond to peripheral nerve injury by up-regulating nitric oxide (NO) production by neurons and glia in addition to local fibroblasts, endothelium and macrophages. We hypothesise that NO produced from these cells has specific roles. We have shown that when neuronal NO synthase (nNOS) is blocked in axotomised DRG, neurons undergo degenerative changes (Thippeswamy et al., 2001, 2007a). Further, we demonstrated that increased neuronal NO production, in response to axotomy/growth factor-deprivation in vitro, signals glial cells to produce trophic factors to support neuronal survival (Thippeswamy et al., 2005a). Recently, we found that treating satellite glia-neuron co-cultures with nNOS inhibitor, 7-nitroindazole (7NI), decreases the number of nestin+ cells that show neuron-like morphology. Cultured/axotomised DRG also upregulate inducible NOS (iNOS) in non-neuronal cells. Therefore, it is plausible that degenerative changes following nNOS inhibition are also due to iNOS-mediated excessive NO production by non-neuronal cells, which indeed is cytotoxic. NG-nitro-l-arginine methylester (L-NAME), the pan NOS inhibitor did not significantly change nNOS+ neuron number in axotomised DRG compared to 7NI suggesting that iNOS-mediated NO contributes to the degenerative process. In this paper, these findings from our and others' past work on NO-mediated neuron-glia signalling in axotomised DRG are discussed.