Fig. 2

Functional terminal density to bursts is regulated by intracellular Mg²⁺ level at individual branches. (a) Colocalization of MgGrn-marked [Mg²⁺]_i and FM4-64-marked functional terminals responding to 5AP bursts input at single branches before (Ctrl 0.8) and after elevating [Mg²⁺]_o for 4 hr (1.2 4hr). (b) N _5AP was linearly correlated with [Mg²⁺]_i (normalized fluorescent intensity of MgGrn) at individual branches before and after elevating [Mg²⁺]_o for 4 hr. Each point represents the data from a branch. (c) [Mg²⁺]_o ‘ON’ and ‘OFF’ experiment. MgGrn marked [Mg²⁺]_i and FM1-43 marked functional terminals responding to 5AP input. “1.2 LT”: elevating [Mg²⁺]_o from 0.8 to 1.2 mM for > 48 hr; “1.2 LT to 0.8 6hr”: decreasing [Mg²⁺]_o from 1.2 to 0.8 mM for 6 hr; “Ctrl + IM 4hr”: adding 1 μM Imipramine (IM) into Ctrl ([Mg²⁺]_o 0.8 mM) for 4 hr. Pseudo-color scale: fluorescent intensity. (d-f) The time-course curves of [Mg²⁺]_i and N _5AP by different treatments shown (c) (n = 5 coverslips for each point). For (c-f), data from sister cultures of the same batch. For (d-f), the mean ± SEM of coverslips was presented. Two-tailed Student’s t-test comparing each time point after [Mg²⁺]_o change to initial [Mg²⁺]_o, *** p < 0.001