EPTA stains all types of SCZs.
(A) EPTA staining does not interfere with immunogold detection, as shown here for SyPhy immunoreactivity, also proving that SyPhy positive synapses (SyPhy+) are readily recognized in EPTA treated material; arrows point to SCZs from the postsynaptic side. Scale bar = 1 µm. (B) Unlike SyPhy immunoreactivity, EPTA does not fail to detect primary sensory endings (co.aff.) indicated by gold-detection of BDA transported into AVCN after intracochlear injection; p = presynapse, d = dendrite. Arrows point to SCZs from the postsynaptic side, arrowhead indicates presynaptic protrusions of an SCZ. Scale bar = 0.5 µm. (C) Glutamate immunogold staining (Glu+) demonstrated in conjunction with EPTA at POD7, indicating that not all glutamatergic synapses have disappeared from AVCN after cochlear nerve degeneration. Arrows point to SCZ from the dendritic side, arrowheads indicate presynaptic protrusions. Scale bar = 1 µm. (D) ChAT immunogold labeling (ChAT+) combined with EPTA staining at POD7; note that the ChAT-positive nerve ending carries an immature SCZ (asterisk), whereas a nearby ChAT-negative synaptic contact (white arrow) shows a fully differentiated EPTA staining including presynaptic protrusions (arrowheads). Scale bar = 1 µm. (E) Gephyrin immunogold labeling (black particles, Geph+) combined with EPTA staining (dark gray). Arrow points to SCZ from the dendritic (d) side, arrowheads indicate presynaptic (p) protrusions. Scale bar = 0.5 µm. (F) GAP-43 immunogold labeling (GAP-43+) combined with EPTA staining. Again, arrow points to SCZ from the dendritic (d) side, arrowhead indicates presynaptic (p) protrusions. Scale bar = 0.5 µm.