The substantia gelatinosa Rolandi of the rat. Fine structure, cytochemistry (acid phosphatase) and changes after dorsal root section

The rat substantia gelatinosa Rolandi (lamina II) was found to contain synaptic glomeruli at the centre of which was a dark terminal (C-terminal) full of round synaptic vesicles. The C-terminal was presynaptic to several dendritic profiles and to terminals containing sparse pleomorphic synaptic vesicles, and was occasionally postsynaptic at symmetrical contacts to other terminals containing numerous pleomorphic vesicles of which about one-third were elongated. Acid phosphatase activity was observed on, and between, the membranes of the synaptic vesicles of the central bouton, as well as in the hyaloplasm of the peripheral elements of the glomeruli. Dorsal root section caused electrondense degeneration of the central boutons. Acid phosphatase activity disappeared from synaptic vesicle membranes in C-boutons, and gradually filled their dense cytoplasmic matrix. The enzyme disappeared completely from the peripheral profiles.