Table 4.
Conventional dyes for neuronal labeling.
| Neuronal dye | Labeling properties | Cell loading | |
|---|---|---|---|
| Cytoplasmic | Hydrazides and Biocytins | Intracellular bidirectional tracer Assesment of gap junctions |
enter cells by microinjection and iontophoresis, may cross gap junctions |
| Dextran conjugates | Intracellular bidirectional tracer |
enter cells by microinjection and through resected neuronal terminals | |
| Membrane-bound | Choleratoxin subunit B (CTB) | membrane-bound bidirectional tracer | Binds to plasma membrane glycosphingolipids |
| Lectins (WGA, Phaseolus Vulgaris, DBA, GS) | membrane-bound bidirectional tracer have limited trans-synaptic labeling capacity (WGA) |
Bind various plasma membrane carbohydrates | |
| DiI | Lateral diffusion in plasma membrane Bidirectional tracer Can be used in live or fixed tissue |
Lipohilic dye, incorporates into lipid bilayer | |
| Functional | AM and FM dyes | Non-fluorescent in aqueous solution, become fluorescent upon internalization | Enter cells by endocytosis or through non-selective ion channels Internalization can be activity-dependent |
| Calcium indicator dyes (Fluo-4, Fura-2) | Become fluorescent upon Ca2+ binding, Activity-dependent |
Esterified dyes are membrane permeable, trapped inside cells after cytoplasmic de-esterification | |
| Voltage-sensetive dye (FluoVolt, ANEP) | Become fluorescent upon changes in electrical potential | Bind plasma membranes (FluoVolt), membrane-permeable (ANEP) |