Like everyone else who does preclinical pain research, I'm always trying to think about better, more objective, more predictive, and higher throughput assays for assessing mouse nociceptive behavior.
While the problems with our bread-and-butter assays (von Frey, Hargreaves, acetone drop, hot plate, etc.) are recognized by all, the reason these assays predominate still is because the alternatives are not much better.
Operant assays such as conditioned place preference/aversion have been used increasingly to assess cognitive/emotional factors of pain, but these assays take a lot of time and training.
What's nice about CPP/CPA is that they can be partially automated and more objective: you put a mouse in a chamber, use video tracking software, and out pops data. The training takes a lot of user input, but the monitoring is automated and user-independent.
In contrast to the conditioned assays, real-time aversion/preference assays don't capture a rodent's memory of a past experience, but rather report on the current aversion/preference that it feels toward a real-time stimulus. This setup is used most now in optogenetic experiments, where light stimulation drives some place preference in the present moment.
In the pain world, people have used peltier floors to drive temperature preference in real time. But mechanical pain is one of the major modalities we test, and there doesn't seem to be a good real-time preference assay for this.
So the idea I'm proposing is the following:
- Make two chamber without any contextual cues ( clear boxes)
Make the floor in one box some kind of material that does not elicit an aversion during in naive animals, but causes aversion after injury/inflammation.: This is the most challenging part I'd say. Possible candidates for flooring are (1) sandpaper of different grit types (2) some fiber such as cotton or wool that can elicit allodynia, (3) synthetic material such as astroturf.
- Monitor behavior using video tracking, or even better, some homemade sensors (beam-breaks) that can be controlled via Arduino or something. This would help with the expense and throughput.
I think the precedence for such an assay setup are there. We use cotton or wool or whatever to elicit dynamic allodynia when applied by an experimenter. Why not if it is part of the floor?
What are your thoughts? Any ideas for the flooring? And what key considerations am I missing here?