To characterize the ionic basis for these effects, we recorded the
whole-cell currents of fresh pericytes before, during, and after
addition of PDGF-BB to the perfusate. Under normal metabolic
conditions, exposure to this molecule reversibly increased both
sustained and transient currents (
Fig. 2A ). Based on earlier experiments,
29 we know that fresh
pericytes have sustained nonspecific cation and potassium conductances,
as well a transiently occurring chloride current. Quantification of
these conductances by methods detailed previously
29 showed
that exposure to PDGF-BB more than doubled the activity of the
nonspecific cation channels (
P = 0.007) and the
chloride channels (
P = 0.017), both of which induce
depolarization of retinal pericytes.
29 However, the
potassium currents were not affected significantly (
P =
0.177) by PDGF-BB. Specifically, in the control group (
n = 39) the nonspecific cation current, potassium current, and chloride
charge transfer were −39 ± 8 pA, 74 ± 17 pA, and −11 ± 2 pC, respectively, and in PDGF-BB (
n = 10) these
values were −87 ± 12 pA, 122 ± 20 pA, and −23 ± 6
pC, respectively. Thus, under normal metabolic conditions PDGF-BB
depolarized pericytes by activating nonspecific cation channels and
chloride channels.