Age-related decrease of potassium currents in glial (Muller) cells of the human retina

Background: Age-dependent alterations have been investigated far less in retinal glial cells than in retinal neurons. We investigated age-dependent alterations of inwardly rectifying potassium (Kir) currents in Muller glial cells of the human retina. Methods: Muller cells were isolated immediately post mortem from donors without a reported history of eye disease, and the amplitudes of Kir currents and of currents through high-voltage-activated (HVA) calcium channels were measured by whole-cell patch clamping. Results: The amplitude of the Kir currents was lower in the cells from donors older than 50 years than in the cells of younger donors; the decrease was strongly correlated with the donor's age (p < 0.001). The current amplitude in the cells from donors older than 60 years was about 40% lower than the amplitude in the cells from donors younger than 50 years. The amplitude of the HVA currents was greater in the cells from donors older than 55 years than in the cells from younger donors; the increase, up to about 500%, was strongly age-dependent (p < 0.001). Interpretation: The age-related decrease in Kir-current amplitude in Muller cells may reflect the neuron loss in the aged retina. Our findings also indicate that retinal glial cells have enhanced cytoplasmic calcium signals in the course of aging.