Fig. 5.

Quantitative analysis of exo-endocytosis based on the comparative uptake of CY3-Syt_lum-Abs and CY2-Syt_lum-Abs. Neurons first were incubated with CY2-Syt_lum-Abs for 10 min in KRH/high K⁺. Then after one additional hour in KRH, which contained tetanus toxin (50 nm) in the case of test condition d, they were incubated with CY3-Syt_lum-Abs for 10 min under the following test conditions: KRH/high K⁺ in a, KRH in b, KRH at 0°C in c, and KRH/high K⁺ in d. Bars represent the ratio between the CY3 and CY2 fluorescence (which was measured at the end of the experiments with a chilled CCD camera) expressed as percentages of the CY3/CY2 ratio observed in the test condition a. Error bars represent SEM.