Ultrastructural changes of afferent nerve terminals in the cat medial geniculate body after destruction of the inferior colliculus.

Three to seven days after destruction of the inferior colliculus, changes of the afferent nerve terminals of the cat medial geniculate body were examined morphometrically by thin sectioning and freeze fracture. The results were compared with those of the control. Three and five days after the operation, postsynaptic densities (PSD) of synapses of the afferent nerve terminals increased their width significantly (p less than 0.01) compared with the control. The packing density of intramembrane particles (IMPs) in aggregates at the synaptic site on the postsynaptic E-face decreased significantly (p less than 0.01) during this period. IMPs of 13 nm in diameter within these aggregates decreased. Ring-shaped IMP aggregates having an IMP free area at the center increased. Width of dense materials of the filamentous contact, which is a non-synaptic contact, decreased significantly (p less than 0.01) 3 and 5 days after the operation as compared with the control, but 7 days after the operation they recovered to the level of the control. No significant change was observed in the intervals of dense materials of the filamentous contact after the operation.