Giraffes

If pain receptors are involved, wouldn't the limit be how much pain triggering neurotransmitter/hormone it would take to saturate all the receptors? Going further, I think approaching this limit would cause a desensitization of the pain response and ultimately lead to down regulation of those receptors. I think this would be the case because pain is just like any other ligand/receptor interaction. After that, prolonged exposure to that pain would probably cause a normalization to the response via down regulation. What I am curious about though, is if the mind amplifies the pain. I do not think this would be the case because it would not help the body experiencing the pain. If you suffer this pain for long enough and are still alive it might not be causing any real detriment to your well being aside from experiencing the pain itself. Therefore, the brain probably has no reason to amplify the pain at all.