As previously shown (Madrid et al, 2009; Noel et al, 2009), the thresholds of cold-sensitive DRG neurons varied over a large range (35 15°C) as demonstrated by the simultaneous recordings of four cold-sensitive neurons from vehicle-treated mice (Fig 3A).
The maximum amplitude of the response, the temperature threshold of cold responses and the cell diameter were also determined.
6 Therefore, the thermal threshold of cold triggered pain should be a reliable, sensitive and quantitative end point for assessing OIPN.
Additionally, this behavioural effect is corroborated by the demonstration that HCN blockade on cold-sensing neurons in vitro is able to increase the threshold of cold detection, thereby directly lowering the excitability of this subclass of nociceptors.
An increased expression of these channels or an alteration in their functional properties could lead to the lower thresholds for cold pain and increased sensitivity to cold seen in neuropathic pain states.
Blocking IKD shifted the activation threshold of noxious cold activated neurons to higher temperatures and it was argued that a similar mechanism could account for cold allodynia.
Their finding of an unchanged warmth threshold agrees with our findings while the increased threshold for cold disagrees with our data.
In case you've forgotten, Magoo first appeared in 1949, at the threshold of the cold war, a weak, bumbling, stumbling character, bullied and pushed around by the more powerful figures around him.
Yet in this current study, changes in both warm (C-fiber) and cold sensation (A-delta fiber) thresholds were observed in all three stimulation duration with the increase of cold threshold temperatures and sustained warm threshold temperature elevation.
Hence we examined combinations of cold thresholds from −5.0 to 5.0°C (in 0.1°C gaps) and hot thresholds from 19.0 to 29.0°C (in 0.1°C gaps) to identify the combination that minimized the residual deviance.
The increase of cold threshold with sustained warm threshold temperature elevation as observed in the longer durations of EA suggests that as the duration of EA lengthened, there is a gradual shifting from an initial predominantly spinally mediated analgesic effect to a supraspinally mediated modulatory mechanism of thermal pain.
