Table 2.

Action potential properties of DRG neurons corresponding to dermatomes with (Pain+) and without (Pain−) pain

Property	Pain	N	Median	Mean	SD	Pain vs no pain
Rheobase (pA)	−	30	600	718	654	MW: U = 971.5, P = 0.0018
	+	103	180	490	718
AP amplitude (mV)	−	27	83.8	83.2	14.2	MW: U = 1018, P = 0.2980
	+	87	88.5	87.0	11.4
AP overshoot (mV)	−	27	63.9	64.1	10.4	Unpaired t test: t = 1.768 P = 0.798
	+	87	59.7	58.8	14.4
AP rise time (ms)	−	27	3.4	12.1	38.3	MW: U = 418, P < 0.0001
	+	87	17.9	40.7	51.7
AP fall time (ms)	−	27	3.7	4.1	2.5	MW: U = 594, P < 0.0001
	+	87	6.4	7.7	5.4
AP half-amplitude duration (ms)	−	27	2.4	3.0	2.0	MW: U = 640, P = 0.0003
	+	87	4.2	4.7	2.6
AHP amplitude (mV)	−	27	−19.3	−19.1	4.3	Unpaired t test: t = 4.128 P < 0.0001
	+	87	−14.1	−14.2	5.6

AP, action potential; AHP, afterhyperpolarization potential; MW: Mann-Whitney U test; SD, standard deviation; t, the t ratio – the difference between sample means divided by standard error of the difference; U, the U value in the Mann Whitney test – the smaller of two calculations counting the number of times that an observation in group A is larger than B, or number of times that an observation in group B is larger than A. Membrane potential measurements are not corrected for the liquid junction potential, so actual values might be up to 15 mV more negative (see Methods).