Advancing age alters rapid and spontaneous refilling of caffeine sensitive calcium stores in sympathetic superior cervical ganglion cells

摘要

Intracellular calcium ([Ca²⁺]i) release from SER stores plays an important role in cell signaling. These stores are rapidly refilled via influx through voltage gated calcium channels or spontaneously via store-operated calcium channels (SOCC), and subsequent pumping by smooth endoplasmic reticulum Ca²⁺ -ATPases (SERCA). We measured [Ca²⁺]i transients in isolated Fura-2 loaded superior cervical ganglion (SCG) cells from 6, 12, 20 and 24 month-old F-344 rats. For rapid refilling, [Ca²⁺]i transients were elicited by a 5 sec exposure to K⁺ (S1), caffeine to release Ca²⁺ from SER stores (S2), K⁺ to refill SER Ca²⁺ stores (S3), and caffeine (S4). The % difference between the peak and rate of rise of the first and second caffeine-evoked [Ca²⁺]i transient significantly declined over the age range of 12–24 months. To estimate spontaneous refilling, cells were depolarized for 5 sec with 68 mM K⁺ (control), followed by a 10 sec exposure to 10 mM caffeine “conditioning stimulus” to deplete [Ca²⁺]i stores. Caffeine was then rapidly applied for 5 sec at defined intervals from 60 to 300 sec. Integrated caffeine-evoked [Ca²⁺]i transients were measured and plotted as a percentage of the K⁺ response vs. time. The derivative of the refilling time curves significantly declined over the age range from 12–24 months. Overall, these data suggest that the ability of SCG cells to sustain release of [Ca²⁺]i, following rapid or spontaneous refilling declines with advancing age. Compromised ability to sustain calcium signaling may possibly alter the overall function of adrenergic neurons innervating the cerebrovasculature.