Figure 2.

Pulsatile low-frequency Ca²⁺ release from the local dendritic ER does not deplete the Ca²⁺ store in soma. A dopamine neuron was stimulated globally or locally by bath application of 20 mm caffeine or by micropressurized application of 50 mm caffeine, respectively. A, A transmitted image shows an isolated neuron and a micropressurized pipette containing 50 mm caffeine. The two different measured areas are circled in different colors, and Ca²⁺ signals are presented in the same color in E. Scale bar, 10 μm. B, A fluorescence ratio (F ₃₄₀/F ₃₈₀) image of fura-2. C, A subtracted ratio image (ΔR), which was obtained by subtraction of a ratio (F ₃₄₀/F ₃₈₀) image before and after global stimulation of a neuron with caffeine, shows a [Ca²⁺]_c rise throughout the soma and dendrites. D, A subtracted ratio image (ΔR) of a neuron before and after local stimulation of caffeine to a dendrite shows local increase in [Ca²⁺]_c only in the stimulated region of a dendrite (red circle in A). E, Global–local–global stimulations with caffeine elicited [Ca²⁺]_c changes in a dendrite (red circle marked in A) and/or in the soma (green circle marked in A), in a stimulation-dependent manner. Local Ca²⁺ releases within a dendrite by local applications of caffeine (number 2) did not affect the second global Ca²⁺ release (number 3) when compared with the first global Ca²⁺ release (number 1), suggesting that the store was not depleted significantly in this condition.