Table 1.

Passive and active electrical properties of LS bladder neurons in the absence and presence of UTP or UTP and suramin application

	No UTP(n = 39)	UTP(n = 21)	UTP + SUR(n = 15)
Current injection
RMP (mV)	−63.9 ± 0.9	−55.6 ± 1.5***	−64.9 ± 2.8 ††
Input resistance (MΩ)	242.0 ± 16.5	224.9 ± 23.0	259.4 ± 17.1
Rheobase (pA)	142.4 ± 11.6	82.2 ± 5.2**	146.2 ± 16.5 ††
AP threshold (mV)	−32.6 ± 0.6	−33.84 ± 1.0	−32.45 ± 1.1
AP amplitude (mV)	107.3 ± 2.1	101.2 ± 2.6	109.3 ± 4.4
AP duration (ms)	4.6 ± 0.5	4.7 ± 0.9	4.3 ± 0.9
AP overshoot (ms)	44.5 ± 1.4	42.0 ± 1.2	46.4 ± 1.8
AP falling rate (mV/ms)	19.3 ± 1.5	18.6 ± 1.6	20.5 ± 1.9
AP frequency, 2× rheobase	3.3 ± 0.5	8.7 ± 1.0**	3.1 ± 0.5 †††
No. of cells firing AP inducedby UTP	0/39	10/21**	0/15 ††
ATP (30 μm)
Depolarization (mV)	20.3 ± 2.6	17.6 ± 3.4	NA
No. of APs	1.1 ± 0.4	2.3 ± 0.8	NA
α,β-met ATP (30 μm)
Depolarization (mV)	13.3 ± 1.7	12.94 ± 1.1	NA
No. of APs	0.8 ± 0.5	1.1 ± 0.6	NA

Input resistance was calculated according to the I–V relationship by injecting a series of hyperpolarizing pulses ranging from −300 to 0 pA (30 ms) in 50 pA increments. To determine rheobase, a series of 10 ms current pulses in 20 pA increments (1 s apart) were injected. The maximum current (in picoamperes) that did not evoke an action potential was taken as rheobase. AP threshold was determined from the inflection point at which membrane potential started to dramatically rise and the phase plot slope (the first derivative of membrane potential, dV/dt) reached 10 mV/ms (Naundorf et al., 2006). AP amplitude was measured from resting membrane potential (RMP) to the peak of the AP, AP overshoot was the amplitude from 0 mV to the peak of the AP, AP duration was determined at 50% of the AP amplitude between the rising and falling phases, and the AP falling rate was the velocity of change in potential from the AP peak to RMP.

**p < 0.01,

***p < 0.005 versus no UTP.

^†† p < 0.01,

^††† p < 0.005 versus UTP application. NA, Not applicable.